sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 428 insertions, 0 deletions

diff --git a/drivers/video/fbdev/ocfb.c b/drivers/video/fbdev/ocfb.c
new file mode 100644
index 000000000..893888260
--- /dev/null
+++ b/drivers/video/fbdev/ocfb.c
@@ -0,0 +1,428 @@
+/*
+ * OpenCores VGA/LCD 2.0 core frame buffer driver
+ *
+ * Copyright (C) 2013 Stefan Kristiansson, stefan.kristiansson@saunalahti.fi
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2.  This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+/* OCFB register defines */
+#define OCFB_CTRL	0x000
+#define OCFB_STAT	0x004
+#define OCFB_HTIM	0x008
+#define OCFB_VTIM	0x00c
+#define OCFB_HVLEN	0x010
+#define OCFB_VBARA	0x014
+#define OCFB_PALETTE	0x800
+
+#define OCFB_CTRL_VEN	0x00000001 /* Video Enable */
+#define OCFB_CTRL_HIE	0x00000002 /* HSync Interrupt Enable */
+#define OCFB_CTRL_PC	0x00000800 /* 8-bit Pseudo Color Enable*/
+#define OCFB_CTRL_CD8	0x00000000 /* Color Depth 8 */
+#define OCFB_CTRL_CD16	0x00000200 /* Color Depth 16 */
+#define OCFB_CTRL_CD24	0x00000400 /* Color Depth 24 */
+#define OCFB_CTRL_CD32	0x00000600 /* Color Depth 32 */
+#define OCFB_CTRL_VBL1	0x00000000 /* Burst Length 1 */
+#define OCFB_CTRL_VBL2	0x00000080 /* Burst Length 2 */
+#define OCFB_CTRL_VBL4	0x00000100 /* Burst Length 4 */
+#define OCFB_CTRL_VBL8	0x00000180 /* Burst Length 8 */
+
+#define PALETTE_SIZE	256
+
+#define OCFB_NAME	"OC VGA/LCD"
+
+static char *mode_option;
+
+static const struct fb_videomode default_mode = {
+	/* 640x480 @ 60 Hz, 31.5 kHz hsync */
+	NULL, 60, 640, 480, 39721, 40, 24, 32, 11, 96, 2,
+	0, FB_VMODE_NONINTERLACED
+};
+
+struct ocfb_dev {
+	struct fb_info info;
+	void __iomem *regs;
+	/* flag indicating whether the regs are little endian accessed */
+	int little_endian;
+	/* Physical and virtual addresses of framebuffer */
+	dma_addr_t fb_phys;
+	void __iomem *fb_virt;
+	u32 pseudo_palette[PALETTE_SIZE];
+};
+
+#ifndef MODULE
+static int __init ocfb_setup(char *options)
+{
+	char *curr_opt;
+
+	if (!options || !*options)
+		return 0;
+
+	while ((curr_opt = strsep(&options, ",")) != NULL) {
+		if (!*curr_opt)
+			continue;
+		mode_option = curr_opt;
+	}
+
+	return 0;
+}
+#endif
+
+static inline u32 ocfb_readreg(struct ocfb_dev *fbdev, loff_t offset)
+{
+	if (fbdev->little_endian)
+		return ioread32(fbdev->regs + offset);
+	else
+		return ioread32be(fbdev->regs + offset);
+}
+
+static void ocfb_writereg(struct ocfb_dev *fbdev, loff_t offset, u32 data)
+{
+	if (fbdev->little_endian)
+		iowrite32(data, fbdev->regs + offset);
+	else
+		iowrite32be(data, fbdev->regs + offset);
+}
+
+static int ocfb_setupfb(struct ocfb_dev *fbdev)
+{
+	unsigned long bpp_config;
+	struct fb_var_screeninfo *var = &fbdev->info.var;
+	struct device *dev = fbdev->info.device;
+	u32 hlen;
+	u32 vlen;
+
+	/* Disable display */
+	ocfb_writereg(fbdev, OCFB_CTRL, 0);
+
+	/* Register framebuffer address */
+	fbdev->little_endian = 0;
+	ocfb_writereg(fbdev, OCFB_VBARA, fbdev->fb_phys);
+
+	/* Detect endianess */
+	if (ocfb_readreg(fbdev, OCFB_VBARA) != fbdev->fb_phys) {
+		fbdev->little_endian = 1;
+		ocfb_writereg(fbdev, OCFB_VBARA, fbdev->fb_phys);
+	}
+
+	/* Horizontal timings */
+	ocfb_writereg(fbdev, OCFB_HTIM, (var->hsync_len - 1) << 24 |
+		      (var->left_margin - 1) << 16 | (var->xres - 1));
+
+	/* Vertical timings */
+	ocfb_writereg(fbdev, OCFB_VTIM, (var->vsync_len - 1) << 24 |
+		      (var->upper_margin - 1) << 16 | (var->yres - 1));
+
+	/* Total length of frame */
+	hlen = var->left_margin + var->right_margin + var->hsync_len +
+		var->xres;
+
+	vlen = var->upper_margin + var->lower_margin + var->vsync_len +
+		var->yres;
+
+	ocfb_writereg(fbdev, OCFB_HVLEN, (hlen - 1) << 16 | (vlen - 1));
+
+	bpp_config = OCFB_CTRL_CD8;
+	switch (var->bits_per_pixel) {
+	case 8:
+		if (!var->grayscale)
+			bpp_config |= OCFB_CTRL_PC;  /* enable palette */
+		break;
+
+	case 16:
+		bpp_config |= OCFB_CTRL_CD16;
+		break;
+
+	case 24:
+		bpp_config |= OCFB_CTRL_CD24;
+		break;
+
+	case 32:
+		bpp_config |= OCFB_CTRL_CD32;
+		break;
+
+	default:
+		dev_err(dev, "no bpp specified\n");
+		break;
+	}
+
+	/* maximum (8) VBL (video memory burst length) */
+	bpp_config |= OCFB_CTRL_VBL8;
+
+	/* Enable output */
+	ocfb_writereg(fbdev, OCFB_CTRL, (OCFB_CTRL_VEN | bpp_config));
+
+	return 0;
+}
+
+static int ocfb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			  unsigned blue, unsigned transp,
+			  struct fb_info *info)
+{
+	struct ocfb_dev *fbdev = (struct ocfb_dev *)info->par;
+	u32 color;
+
+	if (regno >= info->cmap.len) {
+		dev_err(info->device, "regno >= cmap.len\n");
+		return 1;
+	}
+
+	if (info->var.grayscale) {
+		/* grayscale = 0.30*R + 0.59*G + 0.11*B */
+		red = green = blue = (red * 77 + green * 151 + blue * 28) >> 8;
+	}
+
+	red >>= (16 - info->var.red.length);
+	green >>= (16 - info->var.green.length);
+	blue >>= (16 - info->var.blue.length);
+	transp >>= (16 - info->var.transp.length);
+
+	if (info->var.bits_per_pixel == 8 && !info->var.grayscale) {
+		regno <<= 2;
+		color = (red << 16) | (green << 8) | blue;
+		ocfb_writereg(fbdev, OCFB_PALETTE + regno, color);
+	} else {
+		((u32 *)(info->pseudo_palette))[regno] =
+			(red << info->var.red.offset) |
+			(green << info->var.green.offset) |
+			(blue << info->var.blue.offset) |
+			(transp << info->var.transp.offset);
+	}
+
+	return 0;
+}
+
+static int ocfb_init_fix(struct ocfb_dev *fbdev)
+{
+	struct fb_var_screeninfo *var = &fbdev->info.var;
+	struct fb_fix_screeninfo *fix = &fbdev->info.fix;
+
+	strcpy(fix->id, OCFB_NAME);
+
+	fix->line_length = var->xres * var->bits_per_pixel/8;
+	fix->smem_len = fix->line_length * var->yres;
+	fix->type = FB_TYPE_PACKED_PIXELS;
+
+	if (var->bits_per_pixel == 8 && !var->grayscale)
+		fix->visual = FB_VISUAL_PSEUDOCOLOR;
+	else
+		fix->visual = FB_VISUAL_TRUECOLOR;
+
+	return 0;
+}
+
+static int ocfb_init_var(struct ocfb_dev *fbdev)
+{
+	struct fb_var_screeninfo *var = &fbdev->info.var;
+
+	var->accel_flags = FB_ACCEL_NONE;
+	var->activate = FB_ACTIVATE_NOW;
+	var->xres_virtual = var->xres;
+	var->yres_virtual = var->yres;
+
+	switch (var->bits_per_pixel) {
+	case 8:
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		var->red.offset = 0;
+		var->red.length = 8;
+		var->green.offset = 0;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		break;
+
+	case 16:
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		var->red.offset = 11;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 6;
+		var->blue.offset = 0;
+		var->blue.length  = 5;
+		break;
+
+	case 24:
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		var->red.offset = 16;
+		var->red.length = 8;
+		var->green.offset = 8;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		break;
+
+	case 32:
+		var->transp.offset = 24;
+		var->transp.length = 8;
+		var->red.offset = 16;
+		var->red.length = 8;
+		var->green.offset = 8;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		break;
+	}
+
+	return 0;
+}
+
+static const struct fb_ops ocfb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg	= ocfb_setcolreg,
+};
+
+static int ocfb_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+	struct ocfb_dev *fbdev;
+	int fbsize;
+
+	fbdev = devm_kzalloc(&pdev->dev, sizeof(*fbdev), GFP_KERNEL);
+	if (!fbdev)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, fbdev);
+
+	fbdev->info.fbops = &ocfb_ops;
+	fbdev->info.device = &pdev->dev;
+	fbdev->info.par = fbdev;
+
+	/* Video mode setup */
+	if (!fb_find_mode(&fbdev->info.var, &fbdev->info, mode_option,
+			  NULL, 0, &default_mode, 16)) {
+		dev_err(&pdev->dev, "No valid video modes found\n");
+		return -EINVAL;
+	}
+	ocfb_init_var(fbdev);
+	ocfb_init_fix(fbdev);
+
+	fbdev->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fbdev->regs))
+		return PTR_ERR(fbdev->regs);
+
+	/* Allocate framebuffer memory */
+	fbsize = fbdev->info.fix.smem_len;
+	fbdev->fb_virt = dma_alloc_coherent(&pdev->dev, PAGE_ALIGN(fbsize),
+					    &fbdev->fb_phys, GFP_KERNEL);
+	if (!fbdev->fb_virt) {
+		dev_err(&pdev->dev,
+			"Frame buffer memory allocation failed\n");
+		return -ENOMEM;
+	}
+	fbdev->info.fix.smem_start = fbdev->fb_phys;
+	fbdev->info.screen_base = fbdev->fb_virt;
+	fbdev->info.pseudo_palette = fbdev->pseudo_palette;
+
+	/* Clear framebuffer */
+	memset_io(fbdev->fb_virt, 0, fbsize);
+
+	/* Setup and enable the framebuffer */
+	ocfb_setupfb(fbdev);
+
+	if (fbdev->little_endian)
+		fbdev->info.flags |= FBINFO_FOREIGN_ENDIAN;
+
+	/* Allocate color map */
+	ret = fb_alloc_cmap(&fbdev->info.cmap, PALETTE_SIZE, 0);
+	if (ret) {
+		dev_err(&pdev->dev, "Color map allocation failed\n");
+		goto err_dma_free;
+	}
+
+	/* Register framebuffer */
+	ret = register_framebuffer(&fbdev->info);
+	if (ret) {
+		dev_err(&pdev->dev, "Framebuffer registration failed\n");
+		goto err_dealloc_cmap;
+	}
+
+	return 0;
+
+err_dealloc_cmap:
+	fb_dealloc_cmap(&fbdev->info.cmap);
+
+err_dma_free:
+	dma_free_coherent(&pdev->dev, PAGE_ALIGN(fbsize), fbdev->fb_virt,
+			  fbdev->fb_phys);
+
+	return ret;
+}
+
+static void ocfb_remove(struct platform_device *pdev)
+{
+	struct ocfb_dev *fbdev = platform_get_drvdata(pdev);
+
+	unregister_framebuffer(&fbdev->info);
+	fb_dealloc_cmap(&fbdev->info.cmap);
+	dma_free_coherent(&pdev->dev, PAGE_ALIGN(fbdev->info.fix.smem_len),
+			  fbdev->fb_virt, fbdev->fb_phys);
+
+	/* Disable display */
+	ocfb_writereg(fbdev, OCFB_CTRL, 0);
+
+	platform_set_drvdata(pdev, NULL);
+}
+
+static const struct of_device_id ocfb_match[] = {
+	{ .compatible = "opencores,ocfb", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ocfb_match);
+
+static struct platform_driver ocfb_driver = {
+	.probe  = ocfb_probe,
+	.remove = ocfb_remove,
+	.driver = {
+		.name = "ocfb_fb",
+		.of_match_table = ocfb_match,
+	}
+};
+
+/*
+ * Init and exit routines
+ */
+static int __init ocfb_init(void)
+{
+#ifndef MODULE
+	char *option = NULL;
+
+	if (fb_get_options("ocfb", &option))
+		return -ENODEV;
+	ocfb_setup(option);
+#endif
+	return platform_driver_register(&ocfb_driver);
+}
+
+static void __exit ocfb_exit(void)
+{
+	platform_driver_unregister(&ocfb_driver);
+}
+
+module_init(ocfb_init);
+module_exit(ocfb_exit);
+
+MODULE_AUTHOR("Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>");
+MODULE_DESCRIPTION("OpenCores VGA/LCD 2.0 frame buffer driver");
+MODULE_LICENSE("GPL v2");
+module_param(mode_option, charp, 0);
+MODULE_PARM_DESC(mode_option, "Video mode ('<xres>x<yres>[-<bpp>][@refresh]')");