From bb3b2cfeb206f5b10b859e134651b54120e3f530 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linusw@kernel.org>
Date: Tue, 30 Jun 2026 18:05:56 +0100
Subject: ARM: 9480/1: entry: expand comment in __switch_to

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
 drivers/video/fbdev/gbefb.c | 1287 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1287 insertions(+)
 create mode 100644 drivers/video/fbdev/gbefb.c

(limited to 'drivers/video/fbdev/gbefb.c')

diff --git a/drivers/video/fbdev/gbefb.c b/drivers/video/fbdev/gbefb.c
new file mode 100644
index 000000000..cb6ff15a2
--- /dev/null
+++ b/drivers/video/fbdev/gbefb.c
@@ -0,0 +1,1287 @@
+/*
+ *  SGI GBE frame buffer driver
+ *
+ *  Copyright (C) 1999 Silicon Graphics, Inc. - Jeffrey Newquist
+ *  Copyright (C) 2002 Vivien Chappelier <vivien.chappelier@linux-mips.org>
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License. See the file COPYING in the main directory of this archive for
+ *  more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma-direct.h>
+#include <linux/errno.h>
+#include <linux/gfp.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/io.h>
+
+#ifdef CONFIG_MIPS
+#include <asm/addrspace.h>
+#endif
+#include <asm/byteorder.h>
+#include <asm/tlbflush.h>
+
+#include <video/gbe.h>
+
+static struct sgi_gbe *gbe;
+
+struct gbefb_par {
+	struct fb_var_screeninfo var;
+	struct gbe_timing_info timing;
+	int wc_cookie;
+	int valid;
+};
+
+#define GBE_BASE	0x16000000 /* SGI O2 */
+
+/* macro for fastest write-though access to the framebuffer */
+#ifdef CONFIG_MIPS
+#ifdef CONFIG_CPU_R10000
+#define pgprot_fb(_prot) (((_prot) & (~_CACHE_MASK)) | _CACHE_UNCACHED_ACCELERATED)
+#else
+#define pgprot_fb(_prot) (((_prot) & (~_CACHE_MASK)) | _CACHE_CACHABLE_NO_WA)
+#endif
+#endif
+
+/*
+ *  RAM we reserve for the frame buffer. This defines the maximum screen
+ *  size
+ */
+#if CONFIG_FB_GBE_MEM > 8
+#error GBE Framebuffer cannot use more than 8MB of memory
+#endif
+
+#define TILE_SHIFT 16
+#define TILE_SIZE (1 << TILE_SHIFT)
+#define TILE_MASK (TILE_SIZE - 1)
+
+static unsigned int gbe_mem_size = CONFIG_FB_GBE_MEM * 1024*1024;
+static void *gbe_mem;
+static dma_addr_t gbe_dma_addr;
+static phys_addr_t gbe_mem_phys;
+
+static struct {
+	uint16_t *cpu;
+	dma_addr_t dma;
+} gbe_tiles;
+
+static int gbe_revision;
+
+static int ypan, ywrap;
+
+static uint32_t pseudo_palette[16];
+static uint32_t gbe_cmap[256];
+static int gbe_turned_on; /* 0 turned off, 1 turned on */
+
+static char *mode_option = NULL;
+
+/* default CRT mode */
+static struct fb_var_screeninfo default_var_CRT = {
+	/* 640x480, 60 Hz, Non-Interlaced (25.175 MHz dotclock) */
+	.xres		= 640,
+	.yres		= 480,
+	.xres_virtual	= 640,
+	.yres_virtual	= 480,
+	.xoffset	= 0,
+	.yoffset	= 0,
+	.bits_per_pixel	= 8,
+	.grayscale	= 0,
+	.red		= { 0, 8, 0 },
+	.green		= { 0, 8, 0 },
+	.blue		= { 0, 8, 0 },
+	.transp		= { 0, 0, 0 },
+	.nonstd		= 0,
+	.activate	= 0,
+	.height		= -1,
+	.width		= -1,
+	.accel_flags	= 0,
+	.pixclock	= 39722,	/* picoseconds */
+	.left_margin	= 48,
+	.right_margin	= 16,
+	.upper_margin	= 33,
+	.lower_margin	= 10,
+	.hsync_len	= 96,
+	.vsync_len	= 2,
+	.sync		= 0,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+/* default LCD mode */
+static struct fb_var_screeninfo default_var_LCD = {
+	/* 1600x1024, 8 bpp */
+	.xres		= 1600,
+	.yres		= 1024,
+	.xres_virtual	= 1600,
+	.yres_virtual	= 1024,
+	.xoffset	= 0,
+	.yoffset	= 0,
+	.bits_per_pixel	= 8,
+	.grayscale	= 0,
+	.red		= { 0, 8, 0 },
+	.green		= { 0, 8, 0 },
+	.blue		= { 0, 8, 0 },
+	.transp		= { 0, 0, 0 },
+	.nonstd		= 0,
+	.activate	= 0,
+	.height		= -1,
+	.width		= -1,
+	.accel_flags	= 0,
+	.pixclock	= 9353,
+	.left_margin	= 20,
+	.right_margin	= 30,
+	.upper_margin	= 37,
+	.lower_margin	= 3,
+	.hsync_len	= 20,
+	.vsync_len	= 3,
+	.sync		= 0,
+	.vmode		= FB_VMODE_NONINTERLACED
+};
+
+/* default modedb mode */
+/* 640x480, 60 Hz, Non-Interlaced (25.172 MHz dotclock) */
+static struct fb_videomode default_mode_CRT = {
+	.refresh	= 60,
+	.xres		= 640,
+	.yres		= 480,
+	.pixclock	= 39722,
+	.left_margin	= 48,
+	.right_margin	= 16,
+	.upper_margin	= 33,
+	.lower_margin	= 10,
+	.hsync_len	= 96,
+	.vsync_len	= 2,
+	.sync		= 0,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+/* 1600x1024 SGI flatpanel 1600sw */
+static struct fb_videomode default_mode_LCD = {
+	/* 1600x1024, 8 bpp */
+	.xres		= 1600,
+	.yres		= 1024,
+	.pixclock	= 9353,
+	.left_margin	= 20,
+	.right_margin	= 30,
+	.upper_margin	= 37,
+	.lower_margin	= 3,
+	.hsync_len	= 20,
+	.vsync_len	= 3,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static struct fb_videomode *default_mode = &default_mode_CRT;
+static struct fb_var_screeninfo *default_var = &default_var_CRT;
+
+static int flat_panel_enabled = 0;
+
+static void gbe_reset(void)
+{
+	/* Turn on dotclock PLL */
+	gbe->ctrlstat = 0x300aa000;
+}
+
+
+/*
+ * Function:	gbe_turn_off
+ * Parameters:	(None)
+ * Description:	This should turn off the monitor and gbe.  This is used
+ *              when switching between the serial console and the graphics
+ *              console.
+ */
+
+static void gbe_turn_off(void)
+{
+	int i;
+	unsigned int val, y, vpixen_off;
+
+	gbe_turned_on = 0;
+
+	/* check if pixel counter is on */
+	val = gbe->vt_xy;
+	if (GET_GBE_FIELD(VT_XY, FREEZE, val) == 1)
+		return;
+
+	/* turn off DMA */
+	val = gbe->ovr_control;
+	SET_GBE_FIELD(OVR_CONTROL, OVR_DMA_ENABLE, val, 0);
+	gbe->ovr_control = val;
+	udelay(1000);
+	val = gbe->frm_control;
+	SET_GBE_FIELD(FRM_CONTROL, FRM_DMA_ENABLE, val, 0);
+	gbe->frm_control = val;
+	udelay(1000);
+	val = gbe->did_control;
+	SET_GBE_FIELD(DID_CONTROL, DID_DMA_ENABLE, val, 0);
+	gbe->did_control = val;
+	udelay(1000);
+
+	/* We have to wait through two vertical retrace periods before
+	 * the pixel DMA is turned off for sure. */
+	for (i = 0; i < 10000; i++) {
+		val = gbe->frm_inhwctrl;
+		if (GET_GBE_FIELD(FRM_INHWCTRL, FRM_DMA_ENABLE, val)) {
+			udelay(10);
+		} else {
+			val = gbe->ovr_inhwctrl;
+			if (GET_GBE_FIELD(OVR_INHWCTRL, OVR_DMA_ENABLE, val)) {
+				udelay(10);
+			} else {
+				val = gbe->did_inhwctrl;
+				if (GET_GBE_FIELD(DID_INHWCTRL, DID_DMA_ENABLE, val)) {
+					udelay(10);
+				} else
+					break;
+			}
+		}
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn off DMA timed out\n");
+
+	/* wait for vpixen_off */
+	val = gbe->vt_vpixen;
+	vpixen_off = GET_GBE_FIELD(VT_VPIXEN, VPIXEN_OFF, val);
+
+	for (i = 0; i < 100000; i++) {
+		val = gbe->vt_xy;
+		y = GET_GBE_FIELD(VT_XY, Y, val);
+		if (y < vpixen_off)
+			break;
+		udelay(1);
+	}
+	if (i == 100000)
+		printk(KERN_ERR
+		       "gbefb: wait for vpixen_off timed out\n");
+	for (i = 0; i < 10000; i++) {
+		val = gbe->vt_xy;
+		y = GET_GBE_FIELD(VT_XY, Y, val);
+		if (y > vpixen_off)
+			break;
+		udelay(1);
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: wait for vpixen_off timed out\n");
+
+	/* turn off pixel counter */
+	val = 0;
+	SET_GBE_FIELD(VT_XY, FREEZE, val, 1);
+	gbe->vt_xy = val;
+	mdelay(10);
+	for (i = 0; i < 10000; i++) {
+		val = gbe->vt_xy;
+		if (GET_GBE_FIELD(VT_XY, FREEZE, val) != 1)
+			udelay(10);
+		else
+			break;
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn off pixel clock timed out\n");
+
+	/* turn off dot clock */
+	val = gbe->dotclock;
+	SET_GBE_FIELD(DOTCLK, RUN, val, 0);
+	gbe->dotclock = val;
+	mdelay(10);
+	for (i = 0; i < 10000; i++) {
+		val = gbe->dotclock;
+		if (GET_GBE_FIELD(DOTCLK, RUN, val))
+			udelay(10);
+		else
+			break;
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn off dotclock timed out\n");
+
+	/* reset the frame DMA FIFO */
+	val = gbe->frm_size_tile;
+	SET_GBE_FIELD(FRM_SIZE_TILE, FRM_FIFO_RESET, val, 1);
+	gbe->frm_size_tile = val;
+	SET_GBE_FIELD(FRM_SIZE_TILE, FRM_FIFO_RESET, val, 0);
+	gbe->frm_size_tile = val;
+}
+
+static void gbe_turn_on(void)
+{
+	unsigned int val, i;
+
+	/*
+	 * Check if pixel counter is off, for unknown reason this
+	 * code hangs Visual Workstations
+	 */
+	if (gbe_revision < 2) {
+		val = gbe->vt_xy;
+		if (GET_GBE_FIELD(VT_XY, FREEZE, val) == 0)
+			return;
+	}
+
+	/* turn on dot clock */
+	val = gbe->dotclock;
+	SET_GBE_FIELD(DOTCLK, RUN, val, 1);
+	gbe->dotclock = val;
+	mdelay(10);
+	for (i = 0; i < 10000; i++) {
+		val = gbe->dotclock;
+		if (GET_GBE_FIELD(DOTCLK, RUN, val) != 1)
+			udelay(10);
+		else
+			break;
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn on dotclock timed out\n");
+
+	/* turn on pixel counter */
+	val = 0;
+	SET_GBE_FIELD(VT_XY, FREEZE, val, 0);
+	gbe->vt_xy = val;
+	mdelay(10);
+	for (i = 0; i < 10000; i++) {
+		val = gbe->vt_xy;
+		if (GET_GBE_FIELD(VT_XY, FREEZE, val))
+			udelay(10);
+		else
+			break;
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn on pixel clock timed out\n");
+
+	/* turn on DMA */
+	val = gbe->frm_control;
+	SET_GBE_FIELD(FRM_CONTROL, FRM_DMA_ENABLE, val, 1);
+	gbe->frm_control = val;
+	udelay(1000);
+	for (i = 0; i < 10000; i++) {
+		val = gbe->frm_inhwctrl;
+		if (GET_GBE_FIELD(FRM_INHWCTRL, FRM_DMA_ENABLE, val) != 1)
+			udelay(10);
+		else
+			break;
+	}
+	if (i == 10000)
+		printk(KERN_ERR "gbefb: turn on DMA timed out\n");
+
+	gbe_turned_on = 1;
+}
+
+static void gbe_loadcmap(void)
+{
+	int i, j;
+
+	for (i = 0; i < 256; i++) {
+		for (j = 0; j < 1000 && gbe->cm_fifo >= 63; j++)
+			udelay(10);
+		if (j == 1000)
+			printk(KERN_ERR "gbefb: cmap FIFO timeout\n");
+
+		gbe->cmap[i] = gbe_cmap[i];
+	}
+}
+
+/*
+ *  Blank the display.
+ */
+static int gbefb_blank(int blank, struct fb_info *info)
+{
+	/* 0 unblank, 1 blank, 2 no vsync, 3 no hsync, 4 off */
+	switch (blank) {
+	case FB_BLANK_UNBLANK:		/* unblank */
+		gbe_turn_on();
+		gbe_loadcmap();
+		break;
+
+	case FB_BLANK_NORMAL:		/* blank */
+		gbe_turn_off();
+		break;
+
+	default:
+		/* Nothing */
+		break;
+	}
+	return 0;
+}
+
+/*
+ *  Setup flatpanel related registers.
+ */
+static void gbefb_setup_flatpanel(struct gbe_timing_info *timing)
+{
+	int fp_wid, fp_hgt, fp_vbs, fp_vbe;
+	u32 outputVal = 0;
+
+	SET_GBE_FIELD(VT_FLAGS, HDRV_INVERT, outputVal,
+		(timing->flags & FB_SYNC_HOR_HIGH_ACT) ? 0 : 1);
+	SET_GBE_FIELD(VT_FLAGS, VDRV_INVERT, outputVal,
+		(timing->flags & FB_SYNC_VERT_HIGH_ACT) ? 0 : 1);
+	gbe->vt_flags = outputVal;
+
+	/* Turn on the flat panel */
+	fp_wid = 1600;
+	fp_hgt = 1024;
+	fp_vbs = 0;
+	fp_vbe = 1600;
+	timing->pll_m = 4;
+	timing->pll_n = 1;
+	timing->pll_p = 0;
+
+	outputVal = 0;
+	SET_GBE_FIELD(FP_DE, ON, outputVal, fp_vbs);
+	SET_GBE_FIELD(FP_DE, OFF, outputVal, fp_vbe);
+	gbe->fp_de = outputVal;
+	outputVal = 0;
+	SET_GBE_FIELD(FP_HDRV, OFF, outputVal, fp_wid);
+	gbe->fp_hdrv = outputVal;
+	outputVal = 0;
+	SET_GBE_FIELD(FP_VDRV, ON, outputVal, 1);
+	SET_GBE_FIELD(FP_VDRV, OFF, outputVal, fp_hgt + 1);
+	gbe->fp_vdrv = outputVal;
+}
+
+struct gbe_pll_info {
+	int clock_rate;
+	int fvco_min;
+	int fvco_max;
+};
+
+static struct gbe_pll_info gbe_pll_table[2] = {
+	{ 20, 80, 220 },
+	{ 27, 80, 220 },
+};
+
+static int compute_gbe_timing(struct fb_var_screeninfo *var,
+			      struct gbe_timing_info *timing)
+{
+	int pll_m, pll_n, pll_p, error, best_m, best_n, best_p, best_error;
+	int pixclock;
+	struct gbe_pll_info *gbe_pll;
+
+	if (gbe_revision < 2)
+		gbe_pll = &gbe_pll_table[0];
+	else
+		gbe_pll = &gbe_pll_table[1];
+
+	/* Determine valid resolution and timing
+	 * GBE crystal runs at 20Mhz or 27Mhz
+	 * pll_m, pll_n, pll_p define the following frequencies
+	 * fvco = pll_m * 20Mhz / pll_n
+	 * fout = fvco / (2**pll_p) */
+	best_error = 1000000000;
+	best_n = best_m = best_p = 0;
+	for (pll_p = 0; pll_p < 4; pll_p++)
+		for (pll_m = 1; pll_m < 256; pll_m++)
+			for (pll_n = 1; pll_n < 64; pll_n++) {
+				pixclock = (1000000 / gbe_pll->clock_rate) *
+						(pll_n << pll_p) / pll_m;
+
+				error = var->pixclock - pixclock;
+
+				if (error < 0)
+					error = -error;
+
+				if (error < best_error &&
+				    pll_m / pll_n >
+				    gbe_pll->fvco_min / gbe_pll->clock_rate &&
+ 				    pll_m / pll_n <
+				    gbe_pll->fvco_max / gbe_pll->clock_rate) {
+					best_error = error;
+					best_m = pll_m;
+					best_n = pll_n;
+					best_p = pll_p;
+				}
+			}
+
+	if (!best_n || !best_m)
+		return -EINVAL;	/* Resolution to high */
+
+	pixclock = (1000000 / gbe_pll->clock_rate) *
+		(best_n << best_p) / best_m;
+
+	/* set video timing information */
+	if (timing) {
+		timing->width = var->xres;
+		timing->height = var->yres;
+		timing->pll_m = best_m;
+		timing->pll_n = best_n;
+		timing->pll_p = best_p;
+		timing->cfreq = gbe_pll->clock_rate * 1000 * timing->pll_m /
+			(timing->pll_n << timing->pll_p);
+		timing->htotal = var->left_margin + var->xres +
+				var->right_margin + var->hsync_len;
+		timing->vtotal = var->upper_margin + var->yres +
+				var->lower_margin + var->vsync_len;
+		timing->fields_sec = 1000 * timing->cfreq / timing->htotal *
+				1000 / timing->vtotal;
+		timing->hblank_start = var->xres;
+		timing->vblank_start = var->yres;
+		timing->hblank_end = timing->htotal;
+		timing->hsync_start = var->xres + var->right_margin + 1;
+		timing->hsync_end = timing->hsync_start + var->hsync_len;
+		timing->vblank_end = timing->vtotal;
+		timing->vsync_start = var->yres + var->lower_margin + 1;
+		timing->vsync_end = timing->vsync_start + var->vsync_len;
+	}
+
+	return pixclock;
+}
+
+static void gbe_set_timing_info(struct gbe_timing_info *timing)
+{
+	int temp;
+	unsigned int val;
+
+	/* setup dot clock PLL */
+	val = 0;
+	SET_GBE_FIELD(DOTCLK, M, val, timing->pll_m - 1);
+	SET_GBE_FIELD(DOTCLK, N, val, timing->pll_n - 1);
+	SET_GBE_FIELD(DOTCLK, P, val, timing->pll_p);
+	SET_GBE_FIELD(DOTCLK, RUN, val, 0);	/* do not start yet */
+	gbe->dotclock = val;
+	mdelay(10);
+
+	/* setup pixel counter */
+	val = 0;
+	SET_GBE_FIELD(VT_XYMAX, MAXX, val, timing->htotal);
+	SET_GBE_FIELD(VT_XYMAX, MAXY, val, timing->vtotal);
+	gbe->vt_xymax = val;
+
+	/* setup video timing signals */
+	val = 0;
+	SET_GBE_FIELD(VT_VSYNC, VSYNC_ON, val, timing->vsync_start);
+	SET_GBE_FIELD(VT_VSYNC, VSYNC_OFF, val, timing->vsync_end);
+	gbe->vt_vsync = val;
+	val = 0;
+	SET_GBE_FIELD(VT_HSYNC, HSYNC_ON, val, timing->hsync_start);
+	SET_GBE_FIELD(VT_HSYNC, HSYNC_OFF, val, timing->hsync_end);
+	gbe->vt_hsync = val;
+	val = 0;
+	SET_GBE_FIELD(VT_VBLANK, VBLANK_ON, val, timing->vblank_start);
+	SET_GBE_FIELD(VT_VBLANK, VBLANK_OFF, val, timing->vblank_end);
+	gbe->vt_vblank = val;
+	val = 0;
+	SET_GBE_FIELD(VT_HBLANK, HBLANK_ON, val,
+		      timing->hblank_start - 5);
+	SET_GBE_FIELD(VT_HBLANK, HBLANK_OFF, val,
+		      timing->hblank_end - 3);
+	gbe->vt_hblank = val;
+
+	/* setup internal timing signals */
+	val = 0;
+	SET_GBE_FIELD(VT_VCMAP, VCMAP_ON, val, timing->vblank_start);
+	SET_GBE_FIELD(VT_VCMAP, VCMAP_OFF, val, timing->vblank_end);
+	gbe->vt_vcmap = val;
+	val = 0;
+	SET_GBE_FIELD(VT_HCMAP, HCMAP_ON, val, timing->hblank_start);
+	SET_GBE_FIELD(VT_HCMAP, HCMAP_OFF, val, timing->hblank_end);
+	gbe->vt_hcmap = val;
+
+	val = 0;
+	temp = timing->vblank_start - timing->vblank_end - 1;
+	if (temp > 0)
+		temp = -temp;
+
+	if (flat_panel_enabled)
+		gbefb_setup_flatpanel(timing);
+
+	SET_GBE_FIELD(DID_START_XY, DID_STARTY, val, (u32) temp);
+	if (timing->hblank_end >= 20)
+		SET_GBE_FIELD(DID_START_XY, DID_STARTX, val,
+			      timing->hblank_end - 20);
+	else
+		SET_GBE_FIELD(DID_START_XY, DID_STARTX, val,
+			      timing->htotal - (20 - timing->hblank_end));
+	gbe->did_start_xy = val;
+
+	val = 0;
+	SET_GBE_FIELD(CRS_START_XY, CRS_STARTY, val, (u32) (temp + 1));
+	if (timing->hblank_end >= GBE_CRS_MAGIC)
+		SET_GBE_FIELD(CRS_START_XY, CRS_STARTX, val,
+			      timing->hblank_end - GBE_CRS_MAGIC);
+	else
+		SET_GBE_FIELD(CRS_START_XY, CRS_STARTX, val,
+			      timing->htotal - (GBE_CRS_MAGIC -
+						timing->hblank_end));
+	gbe->crs_start_xy = val;
+
+	val = 0;
+	SET_GBE_FIELD(VC_START_XY, VC_STARTY, val, (u32) temp);
+	SET_GBE_FIELD(VC_START_XY, VC_STARTX, val, timing->hblank_end - 4);
+	gbe->vc_start_xy = val;
+
+	val = 0;
+	temp = timing->hblank_end - GBE_PIXEN_MAGIC_ON;
+	if (temp < 0)
+		temp += timing->htotal;	/* allow blank to wrap around */
+
+	SET_GBE_FIELD(VT_HPIXEN, HPIXEN_ON, val, temp);
+	SET_GBE_FIELD(VT_HPIXEN, HPIXEN_OFF, val,
+		      ((temp + timing->width -
+			GBE_PIXEN_MAGIC_OFF) % timing->htotal));
+	gbe->vt_hpixen = val;
+
+	val = 0;
+	SET_GBE_FIELD(VT_VPIXEN, VPIXEN_ON, val, timing->vblank_end);
+	SET_GBE_FIELD(VT_VPIXEN, VPIXEN_OFF, val, timing->vblank_start);
+	gbe->vt_vpixen = val;
+
+	/* turn off sync on green */
+	val = 0;
+	SET_GBE_FIELD(VT_FLAGS, SYNC_LOW, val, 1);
+	gbe->vt_flags = val;
+}
+
+/*
+ *  Set the hardware according to 'par'.
+ */
+
+static int gbefb_set_par(struct fb_info *info)
+{
+	int i;
+	unsigned int val;
+	int wholeTilesX, partTilesX, maxPixelsPerTileX;
+	int height_pix;
+	int xpmax, ypmax;	/* Monitor resolution */
+	int bytesPerPixel;	/* Bytes per pixel */
+	struct gbefb_par *par = (struct gbefb_par *) info->par;
+
+	compute_gbe_timing(&info->var, &par->timing);
+
+	bytesPerPixel = info->var.bits_per_pixel / 8;
+	info->fix.line_length = info->var.xres_virtual * bytesPerPixel;
+	xpmax = par->timing.width;
+	ypmax = par->timing.height;
+
+	/* turn off GBE */
+	gbe_turn_off();
+
+	/* set timing info */
+	gbe_set_timing_info(&par->timing);
+
+	/* initialize DIDs */
+	val = 0;
+	switch (bytesPerPixel) {
+	case 1:
+		SET_GBE_FIELD(WID, TYP, val, GBE_CMODE_I8);
+		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
+		break;
+	case 2:
+		SET_GBE_FIELD(WID, TYP, val, GBE_CMODE_ARGB5);
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		break;
+	case 4:
+		SET_GBE_FIELD(WID, TYP, val, GBE_CMODE_RGB8);
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		break;
+	}
+	SET_GBE_FIELD(WID, BUF, val, GBE_BMODE_BOTH);
+
+	for (i = 0; i < 32; i++)
+		gbe->mode_regs[i] = val;
+
+	/* Initialize interrupts */
+	gbe->vt_intr01 = 0xffffffff;
+	gbe->vt_intr23 = 0xffffffff;
+
+	/* HACK:
+	   The GBE hardware uses a tiled memory to screen mapping. Tiles are
+	   blocks of 512x128, 256x128 or 128x128 pixels, respectively for 8bit,
+	   16bit and 32 bit modes (64 kB). They cover the screen with partial
+	   tiles on the right and/or bottom of the screen if needed.
+	   For example in 640x480 8 bit mode the mapping is:
+
+	   <-------- 640 ----->
+	   <---- 512 ----><128|384 offscreen>
+	   ^  ^
+	   | 128    [tile 0]        [tile 1]
+	   |  v
+	   ^
+	   4 128    [tile 2]        [tile 3]
+	   8  v
+	   0  ^
+	   128    [tile 4]        [tile 5]
+	   |  v
+	   |  ^
+	   v  96    [tile 6]        [tile 7]
+	   32 offscreen
+
+	   Tiles have the advantage that they can be allocated individually in
+	   memory. However, this mapping is not linear at all, which is not
+	   really convenient. In order to support linear addressing, the GBE
+	   DMA hardware is fooled into thinking the screen is only one tile
+	   large and but has a greater height, so that the DMA transfer covers
+	   the same region.
+	   Tiles are still allocated as independent chunks of 64KB of
+	   continuous physical memory and remapped so that the kernel sees the
+	   framebuffer as a continuous virtual memory. The GBE tile table is
+	   set up so that each tile references one of these 64k blocks:
+
+	   GBE -> tile list    framebuffer           TLB   <------------ CPU
+	          [ tile 0 ] -> [ 64KB ]  <- [ 16x 4KB page entries ]     ^
+	             ...           ...              ...       linear virtual FB
+	          [ tile n ] -> [ 64KB ]  <- [ 16x 4KB page entries ]     v
+
+
+	   The GBE hardware is then told that the buffer is 512*tweaked_height,
+	   with tweaked_height = real_width*real_height/pixels_per_tile.
+	   Thus the GBE hardware will scan the first tile, filing the first 64k
+	   covered region of the screen, and then will proceed to the next
+	   tile, until the whole screen is covered.
+
+	   Here is what would happen at 640x480 8bit:
+
+	   normal tiling               linear
+	   ^   11111111111111112222    11111111111111111111  ^
+	   128 11111111111111112222    11111111111111111111 102 lines
+	       11111111111111112222    11111111111111111111  v
+	   V   11111111111111112222    11111111222222222222
+	       33333333333333334444    22222222222222222222
+	       33333333333333334444    22222222222222222222
+	       <      512     >        <  256 >               102*640+256 = 64k
+
+	   NOTE: The only mode for which this is not working is 800x600 8bit,
+	   as 800*600/512 = 937.5 which is not integer and thus causes
+	   flickering.
+	   I guess this is not so important as one can use 640x480 8bit or
+	   800x600 16bit anyway.
+	 */
+
+	/* Tell gbe about the tiles table location */
+	/* tile_ptr -> [ tile 1 ] -> FB mem */
+	/*             [ tile 2 ] -> FB mem */
+	/*               ...                */
+	val = 0;
+	SET_GBE_FIELD(FRM_CONTROL, FRM_TILE_PTR, val, gbe_tiles.dma >> 9);
+	SET_GBE_FIELD(FRM_CONTROL, FRM_DMA_ENABLE, val, 0); /* do not start */
+	SET_GBE_FIELD(FRM_CONTROL, FRM_LINEAR, val, 0);
+	gbe->frm_control = val;
+
+	maxPixelsPerTileX = 512 / bytesPerPixel;
+	wholeTilesX = 1;
+	partTilesX = 0;
+
+	/* Initialize the framebuffer */
+	val = 0;
+	SET_GBE_FIELD(FRM_SIZE_TILE, FRM_WIDTH_TILE, val, wholeTilesX);
+	SET_GBE_FIELD(FRM_SIZE_TILE, FRM_RHS, val, partTilesX);
+
+	switch (bytesPerPixel) {
+	case 1:
+		SET_GBE_FIELD(FRM_SIZE_TILE, FRM_DEPTH, val,
+			      GBE_FRM_DEPTH_8);
+		break;
+	case 2:
+		SET_GBE_FIELD(FRM_SIZE_TILE, FRM_DEPTH, val,
+			      GBE_FRM_DEPTH_16);
+		break;
+	case 4:
+		SET_GBE_FIELD(FRM_SIZE_TILE, FRM_DEPTH, val,
+			      GBE_FRM_DEPTH_32);
+		break;
+	}
+	gbe->frm_size_tile = val;
+
+	/* compute tweaked height */
+	height_pix = xpmax * ypmax / maxPixelsPerTileX;
+
+	val = 0;
+	SET_GBE_FIELD(FRM_SIZE_PIXEL, FB_HEIGHT_PIX, val, height_pix);
+	gbe->frm_size_pixel = val;
+
+	/* turn off DID and overlay DMA */
+	gbe->did_control = 0;
+	gbe->ovr_width_tile = 0;
+
+	/* Turn off mouse cursor */
+	gbe->crs_ctl = 0;
+
+	/* Turn on GBE */
+	gbe_turn_on();
+
+	/* Initialize the gamma map */
+	udelay(10);
+	for (i = 0; i < 256; i++)
+		gbe->gmap[i] = (i << 24) | (i << 16) | (i << 8);
+
+	/* Initialize the color map */
+	for (i = 0; i < 256; i++)
+		gbe_cmap[i] = (i << 8) | (i << 16) | (i << 24);
+
+	gbe_loadcmap();
+
+	return 0;
+}
+
+static void gbefb_encode_fix(struct fb_fix_screeninfo *fix,
+			     struct fb_var_screeninfo *var)
+{
+	memset(fix, 0, sizeof(struct fb_fix_screeninfo));
+	strcpy(fix->id, "SGI GBE");
+	fix->smem_start = (unsigned long) gbe_mem;
+	fix->smem_len = gbe_mem_size;
+	fix->type = FB_TYPE_PACKED_PIXELS;
+	fix->type_aux = 0;
+	fix->accel = FB_ACCEL_NONE;
+	switch (var->bits_per_pixel) {
+	case 8:
+		fix->visual = FB_VISUAL_PSEUDOCOLOR;
+		break;
+	default:
+		fix->visual = FB_VISUAL_TRUECOLOR;
+		break;
+	}
+	fix->ywrapstep = 0;
+	fix->xpanstep = 0;
+	fix->ypanstep = 0;
+	fix->line_length = var->xres_virtual * var->bits_per_pixel / 8;
+	fix->mmio_start = GBE_BASE;
+	fix->mmio_len = sizeof(struct sgi_gbe);
+}
+
+/*
+ *  Set a single color register. The values supplied are already
+ *  rounded down to the hardware's capabilities (according to the
+ *  entries in the var structure). Return != 0 for invalid regno.
+ */
+
+static int gbefb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			     unsigned blue, unsigned transp,
+			     struct fb_info *info)
+{
+	int i;
+
+	if (regno > 255)
+		return 1;
+	red >>= 8;
+	green >>= 8;
+	blue >>= 8;
+
+	if (info->var.bits_per_pixel <= 8) {
+		gbe_cmap[regno] = (red << 24) | (green << 16) | (blue << 8);
+		if (gbe_turned_on) {
+			/* wait for the color map FIFO to have a free entry */
+			for (i = 0; i < 1000 && gbe->cm_fifo >= 63; i++)
+				udelay(10);
+			if (i == 1000) {
+				printk(KERN_ERR "gbefb: cmap FIFO timeout\n");
+				return 1;
+			}
+			gbe->cmap[regno] = gbe_cmap[regno];
+		}
+	} else if (regno < 16) {
+		switch (info->var.bits_per_pixel) {
+		case 15:
+		case 16:
+			red >>= 3;
+			green >>= 3;
+			blue >>= 3;
+			pseudo_palette[regno] =
+				(red << info->var.red.offset) |
+				(green << info->var.green.offset) |
+				(blue << info->var.blue.offset);
+			break;
+		case 32:
+			pseudo_palette[regno] =
+				(red << info->var.red.offset) |
+				(green << info->var.green.offset) |
+				(blue << info->var.blue.offset);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ *  Check video mode validity, eventually modify var to best match.
+ */
+static int gbefb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	unsigned int line_length;
+	struct gbe_timing_info timing;
+	int ret;
+
+	/* Limit bpp to 8, 16, and 32 */
+	if (var->bits_per_pixel <= 8)
+		var->bits_per_pixel = 8;
+	else if (var->bits_per_pixel <= 16)
+		var->bits_per_pixel = 16;
+	else if (var->bits_per_pixel <= 32)
+		var->bits_per_pixel = 32;
+	else
+		return -EINVAL;
+
+	/* Check the mode can be mapped linearly with the tile table trick. */
+	/* This requires width x height x bytes/pixel be a multiple of 512 */
+	if ((var->xres * var->yres * var->bits_per_pixel) & 4095)
+		return -EINVAL;
+
+	var->grayscale = 0;	/* No grayscale for now */
+
+	ret = compute_gbe_timing(var, &timing);
+	var->pixclock = ret;
+	if (ret < 0)
+		return -EINVAL;
+
+	/* Adjust virtual resolution, if necessary */
+	if (var->xres > var->xres_virtual || (!ywrap && !ypan))
+		var->xres_virtual = var->xres;
+	if (var->yres > var->yres_virtual || (!ywrap && !ypan))
+		var->yres_virtual = var->yres;
+
+	if (var->vmode & FB_VMODE_CONUPDATE) {
+		var->vmode |= FB_VMODE_YWRAP;
+		var->xoffset = info->var.xoffset;
+		var->yoffset = info->var.yoffset;
+	}
+
+	/* No grayscale for now */
+	var->grayscale = 0;
+
+	/* Memory limit */
+	line_length = var->xres_virtual * var->bits_per_pixel / 8;
+	if (line_length * var->yres_virtual > gbe_mem_size)
+		return -ENOMEM;	/* Virtual resolution too high */
+
+	switch (var->bits_per_pixel) {
+	case 8:
+		var->red.offset = 0;
+		var->red.length = 8;
+		var->green.offset = 0;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case 16:		/* RGB 1555 */
+		var->red.offset = 10;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 5;
+		var->blue.offset = 0;
+		var->blue.length = 5;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case 32:		/* RGB 8888 */
+		var->red.offset = 24;
+		var->red.length = 8;
+		var->green.offset = 16;
+		var->green.length = 8;
+		var->blue.offset = 8;
+		var->blue.length = 8;
+		var->transp.offset = 0;
+		var->transp.length = 8;
+		break;
+	}
+	var->red.msb_right = 0;
+	var->green.msb_right = 0;
+	var->blue.msb_right = 0;
+	var->transp.msb_right = 0;
+
+	var->left_margin = timing.htotal - timing.hsync_end;
+	var->right_margin = timing.hsync_start - timing.width;
+	var->upper_margin = timing.vtotal - timing.vsync_end;
+	var->lower_margin = timing.vsync_start - timing.height;
+	var->hsync_len = timing.hsync_end - timing.hsync_start;
+	var->vsync_len = timing.vsync_end - timing.vsync_start;
+
+	return 0;
+}
+
+static int gbefb_mmap(struct fb_info *info,
+			struct vm_area_struct *vma)
+{
+	unsigned long size = vma->vm_end - vma->vm_start;
+	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+	unsigned long addr;
+	unsigned long phys_addr, phys_size;
+	u16 *tile;
+
+	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
+
+	/* check range */
+	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
+		return -EINVAL;
+	if (size > gbe_mem_size)
+		return -EINVAL;
+	if (offset > gbe_mem_size - size)
+		return -EINVAL;
+
+	/* remap using the fastest write-through mode on architecture */
+	/* try not polluting the cache when possible */
+#ifdef CONFIG_MIPS
+	pgprot_val(vma->vm_page_prot) =
+		pgprot_fb(pgprot_val(vma->vm_page_prot));
+#endif
+	/* VM_IO | VM_DONTEXPAND | VM_DONTDUMP are set by remap_pfn_range() */
+
+	/* look for the starting tile */
+	tile = &gbe_tiles.cpu[offset >> TILE_SHIFT];
+	addr = vma->vm_start;
+	offset &= TILE_MASK;
+
+	/* remap each tile separately */
+	do {
+		phys_addr = (((unsigned long) (*tile)) << TILE_SHIFT) + offset;
+		if ((offset + size) < TILE_SIZE)
+			phys_size = size;
+		else
+			phys_size = TILE_SIZE - offset;
+
+		if (remap_pfn_range(vma, addr, phys_addr >> PAGE_SHIFT,
+						phys_size, vma->vm_page_prot))
+			return -EAGAIN;
+
+		offset = 0;
+		size -= phys_size;
+		addr += phys_size;
+		tile++;
+	} while (size);
+
+	return 0;
+}
+
+static const struct fb_ops gbefb_ops = {
+	.owner		= THIS_MODULE,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
+	.fb_check_var	= gbefb_check_var,
+	.fb_set_par	= gbefb_set_par,
+	.fb_setcolreg	= gbefb_setcolreg,
+	.fb_blank	= gbefb_blank,
+	__FB_DEFAULT_IOMEM_OPS_DRAW,
+	.fb_mmap	= gbefb_mmap,
+};
+
+/*
+ * sysfs
+ */
+
+static ssize_t gbefb_show_memsize(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%u\n", gbe_mem_size);
+}
+
+static DEVICE_ATTR(size, S_IRUGO, gbefb_show_memsize, NULL);
+
+static ssize_t gbefb_show_rev(struct device *device, struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", gbe_revision);
+}
+
+static DEVICE_ATTR(revision, S_IRUGO, gbefb_show_rev, NULL);
+
+static struct attribute *gbefb_attrs[] = {
+	&dev_attr_size.attr,
+	&dev_attr_revision.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(gbefb);
+
+/*
+ * Initialization
+ */
+
+static int gbefb_setup(char *options)
+{
+	char *this_opt;
+
+	if (!options || !*options)
+		return 0;
+
+	while ((this_opt = strsep(&options, ",")) != NULL) {
+		if (!strncmp(this_opt, "monitor:", 8)) {
+			if (!strncmp(this_opt + 8, "crt", 3)) {
+				flat_panel_enabled = 0;
+				default_var = &default_var_CRT;
+				default_mode = &default_mode_CRT;
+			} else if (!strncmp(this_opt + 8, "1600sw", 6) ||
+				   !strncmp(this_opt + 8, "lcd", 3)) {
+				flat_panel_enabled = 1;
+				default_var = &default_var_LCD;
+				default_mode = &default_mode_LCD;
+			}
+		} else if (!strncmp(this_opt, "mem:", 4)) {
+			gbe_mem_size = memparse(this_opt + 4, &this_opt);
+			if (gbe_mem_size > CONFIG_FB_GBE_MEM * 1024 * 1024)
+				gbe_mem_size = CONFIG_FB_GBE_MEM * 1024 * 1024;
+			if (gbe_mem_size < TILE_SIZE)
+				gbe_mem_size = TILE_SIZE;
+		} else
+			mode_option = this_opt;
+	}
+	return 0;
+}
+
+static int gbefb_probe(struct platform_device *p_dev)
+{
+	int i, ret = 0;
+	struct fb_info *info;
+	struct gbefb_par *par;
+#ifndef MODULE
+	char *options = NULL;
+#endif
+
+	info = framebuffer_alloc(sizeof(struct gbefb_par), &p_dev->dev);
+	if (!info)
+		return -ENOMEM;
+
+#ifndef MODULE
+	if (fb_get_options("gbefb", &options)) {
+		ret = -ENODEV;
+		goto out_release_framebuffer;
+	}
+	gbefb_setup(options);
+#endif
+
+	if (!request_mem_region(GBE_BASE, sizeof(struct sgi_gbe), "GBE")) {
+		printk(KERN_ERR "gbefb: couldn't reserve mmio region\n");
+		ret = -EBUSY;
+		goto out_release_framebuffer;
+	}
+
+	gbe = (struct sgi_gbe *) devm_ioremap(&p_dev->dev, GBE_BASE,
+					      sizeof(struct sgi_gbe));
+	if (!gbe) {
+		printk(KERN_ERR "gbefb: couldn't map mmio region\n");
+		ret = -ENXIO;
+		goto out_release_mem_region;
+	}
+	gbe_revision = gbe->ctrlstat & 15;
+
+	gbe_tiles.cpu = dmam_alloc_coherent(&p_dev->dev,
+				GBE_TLB_SIZE * sizeof(uint16_t),
+				&gbe_tiles.dma, GFP_KERNEL);
+	if (!gbe_tiles.cpu) {
+		printk(KERN_ERR "gbefb: couldn't allocate tiles table\n");
+		ret = -ENOMEM;
+		goto out_release_mem_region;
+	}
+
+	if (gbe_mem_phys) {
+		/* memory was allocated at boot time */
+		gbe_mem = devm_ioremap_wc(&p_dev->dev, gbe_mem_phys,
+					  gbe_mem_size);
+		if (!gbe_mem) {
+			printk(KERN_ERR "gbefb: couldn't map framebuffer\n");
+			ret = -ENOMEM;
+			goto out_release_mem_region;
+		}
+
+		gbe_dma_addr = 0;
+	} else {
+		/* try to allocate memory with the classical allocator
+		 * this has high chance to fail on low memory machines */
+		gbe_mem = dmam_alloc_attrs(&p_dev->dev, gbe_mem_size,
+				&gbe_dma_addr, GFP_KERNEL,
+				DMA_ATTR_WRITE_COMBINE);
+		if (!gbe_mem) {
+			printk(KERN_ERR "gbefb: couldn't allocate framebuffer memory\n");
+			ret = -ENOMEM;
+			goto out_release_mem_region;
+		}
+
+		gbe_mem_phys = dma_to_phys(&p_dev->dev, gbe_dma_addr);
+	}
+
+	par = info->par;
+	par->wc_cookie = arch_phys_wc_add(gbe_mem_phys, gbe_mem_size);
+
+	/* map framebuffer memory into tiles table */
+	for (i = 0; i < (gbe_mem_size >> TILE_SHIFT); i++)
+		gbe_tiles.cpu[i] = (gbe_mem_phys >> TILE_SHIFT) + i;
+
+	info->fbops = &gbefb_ops;
+	info->pseudo_palette = pseudo_palette;
+	info->screen_base = gbe_mem;
+	fb_alloc_cmap(&info->cmap, 256, 0);
+
+	/* reset GBE */
+	gbe_reset();
+
+	/* turn on default video mode */
+	if (fb_find_mode(&par->var, info, mode_option, NULL, 0,
+			 default_mode, 8) == 0)
+		par->var = *default_var;
+	info->var = par->var;
+	gbefb_check_var(&par->var, info);
+	gbefb_encode_fix(&info->fix, &info->var);
+
+	if (register_framebuffer(info) < 0) {
+		printk(KERN_ERR "gbefb: couldn't register framebuffer\n");
+		ret = -ENXIO;
+		goto out_gbe_unmap;
+	}
+
+	platform_set_drvdata(p_dev, info);
+
+	fb_info(info, "%s rev %d @ 0x%08x using %dkB memory\n",
+		info->fix.id, gbe_revision, (unsigned)GBE_BASE,
+		gbe_mem_size >> 10);
+
+	return 0;
+
+out_gbe_unmap:
+	arch_phys_wc_del(par->wc_cookie);
+out_release_mem_region:
+	release_mem_region(GBE_BASE, sizeof(struct sgi_gbe));
+out_release_framebuffer:
+	framebuffer_release(info);
+
+	return ret;
+}
+
+static void gbefb_remove(struct platform_device* p_dev)
+{
+	struct fb_info *info = platform_get_drvdata(p_dev);
+	struct gbefb_par *par = info->par;
+
+	unregister_framebuffer(info);
+	gbe_turn_off();
+	arch_phys_wc_del(par->wc_cookie);
+	release_mem_region(GBE_BASE, sizeof(struct sgi_gbe));
+	framebuffer_release(info);
+}
+
+static struct platform_driver gbefb_driver = {
+	.probe = gbefb_probe,
+	.remove = gbefb_remove,
+	.driver = {
+		.name = "gbefb",
+		.dev_groups = gbefb_groups,
+	},
+};
+
+static struct platform_device *gbefb_device;
+
+static int __init gbefb_init(void)
+{
+	int ret = platform_driver_register(&gbefb_driver);
+	if (IS_ENABLED(CONFIG_SGI_IP32) && !ret) {
+		gbefb_device = platform_device_alloc("gbefb", 0);
+		if (gbefb_device) {
+			ret = platform_device_add(gbefb_device);
+		} else {
+			ret = -ENOMEM;
+		}
+		if (ret) {
+			platform_device_put(gbefb_device);
+			platform_driver_unregister(&gbefb_driver);
+		}
+	}
+	return ret;
+}
+
+static void __exit gbefb_exit(void)
+{
+	platform_device_unregister(gbefb_device);
+	platform_driver_unregister(&gbefb_driver);
+}
+
+module_init(gbefb_init);
+module_exit(gbefb_exit);
+
+MODULE_LICENSE("GPL");
-- 
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