iio: proximity: vl53l0x-i2c: claim direct mode for raw readsgrafted

vl53l0x_read_raw() starts a single-shot ranging measurement and reads
back the result. Once the triggered buffer is enabled the sensor runs in
continuous mode and its data-ready interrupt is routed to the trigger,
so a concurrent in_distance_raw read disturbs the streaming setup and
never gets its completion, returning -ETIMEDOUT.

The original submission claimed direct mode here, but it was dropped
during review because the driver had no buffer support at the time [1].
Continuous (buffered) mode was later added without restoring the
claim [2], reintroducing the conflict.

Reject direct reads while buffered capture is active by claiming direct
mode around the measurement, as the vl53l1x sibling already does.

Fixes: 762186c6e7b1 ("iio: proximity: vl53l0x-i2c: Added continuous mode support")
Link: https://lore.kernel.org/linux-iio/20180911160300.GA9212@himanshu-Vostro-3559/ [1]
Link: https://lore.kernel.org/linux-iio/20240909101508.263085-3-abhashkumarjha123@gmail.com/ [2]
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

1 files changed, 101 insertions, 0 deletions

diff --git a/drivers/mtd/devices/ms02-nv.h b/drivers/mtd/devices/ms02-nv.h
new file mode 100644
index 000000000..737e4735d
--- /dev/null
+++ b/drivers/mtd/devices/ms02-nv.h
@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *	Copyright (c) 2001, 2003  Maciej W. Rozycki
+ *
+ *	DEC MS02-NV (54-20948-01) battery backed-up NVRAM module for
+ *	DECstation/DECsystem 5000/2x0 and DECsystem 5900 and 5900/260
+ *	systems.
+ */
+
+#include <linux/ioport.h>
+#include <linux/mtd/mtd.h>
+
+/*
+ * Addresses are decoded as follows:
+ *
+ * 0x000000 - 0x3fffff	SRAM
+ * 0x400000 - 0x7fffff	CSR
+ *
+ * Within the SRAM area the following ranges are forced by the system
+ * firmware:
+ *
+ * 0x000000 - 0x0003ff	diagnostic area, destroyed upon a reboot
+ * 0x000400 - ENDofRAM	storage area, available to operating systems
+ *
+ * but we can't really use the available area right from 0x000400 as
+ * the first word is used by the firmware as a status flag passed
+ * from an operating system.  If anything but the valid data magic
+ * ID value is found, the firmware considers the SRAM clean, i.e.
+ * containing no valid data, and disables the battery resulting in
+ * data being erased as soon as power is switched off.  So the choice
+ * for the start address of the user-available is 0x001000 which is
+ * nicely page aligned.  The area between 0x000404 and 0x000fff may
+ * be used by the driver for own needs.
+ *
+ * The diagnostic area defines two status words to be read by an
+ * operating system, a magic ID to distinguish a MS02-NV board from
+ * anything else and a status information providing results of tests
+ * as well as the size of SRAM available, which can be 1MiB or 2MiB
+ * (that's what the firmware handles; no idea if 2MiB modules ever
+ * existed).
+ *
+ * The firmware only handles the MS02-NV board if installed in the
+ * last (15th) slot, so for any other location the status information
+ * stored in the SRAM cannot be relied upon.  But from the hardware
+ * point of view there is no problem using up to 14 such boards in a
+ * system -- only the 1st slot needs to be filled with a DRAM module.
+ * The MS02-NV board is ECC-protected, like other MS02 memory boards.
+ *
+ * The state of the battery as provided by the CSR is reflected on
+ * the two onboard LEDs.  When facing the battery side of the board,
+ * with the LEDs at the top left and the battery at the bottom right
+ * (i.e. looking from the back side of the system box), their meaning
+ * is as follows (the system has to be powered on):
+ *
+ * left LED		battery disable status: lit = enabled
+ * right LED		battery condition status: lit = OK
+ */
+
+/* MS02-NV iomem register offsets. */
+#define MS02NV_CSR		0x400000	/* control & status register */
+
+/* MS02-NV CSR status bits. */
+#define MS02NV_CSR_BATT_OK	0x01		/* battery OK */
+#define MS02NV_CSR_BATT_OFF	0x02		/* battery disabled */
+
+
+/* MS02-NV memory offsets. */
+#define MS02NV_DIAG		0x0003f8	/* diagnostic status */
+#define MS02NV_MAGIC		0x0003fc	/* MS02-NV magic ID */
+#define MS02NV_VALID		0x000400	/* valid data magic ID */
+#define MS02NV_RAM		0x001000	/* user-exposed RAM start */
+
+/* MS02-NV diagnostic status bits. */
+#define MS02NV_DIAG_TEST	0x01		/* SRAM test done (?) */
+#define MS02NV_DIAG_RO		0x02		/* SRAM r/o test done */
+#define MS02NV_DIAG_RW		0x04		/* SRAM r/w test done */
+#define MS02NV_DIAG_FAIL	0x08		/* SRAM test failed */
+#define MS02NV_DIAG_SIZE_MASK	0xf0		/* SRAM size mask */
+#define MS02NV_DIAG_SIZE_SHIFT	0x10		/* SRAM size shift (left) */
+
+/* MS02-NV general constants. */
+#define MS02NV_ID		0x03021966	/* MS02-NV magic ID value */
+#define MS02NV_VALID_ID		0xbd100248	/* valid data magic ID value */
+#define MS02NV_SLOT_SIZE	0x800000	/* size of the address space
+						   decoded by the module */
+
+
+typedef volatile u32 ms02nv_uint;
+
+struct ms02nv_private {
+	struct mtd_info *next;
+	struct {
+		struct resource *module;
+		struct resource *diag_ram;
+		struct resource *user_ram;
+		struct resource *csr;
+	} resource;
+	u_char *addr;
+	size_t size;
+	u_char *uaddr;
+};