[PATCH 08/10] drm/i915/spi: align 64bit read and write

[Alexander Usyskin]

GSC SPI HW errors on quad access overlapping 1K border.
Align 64bit read and write to avoid readq/writeq over 1K border.

Signed-off-by: Alexander Usyskin <alexander.usyskin at intel.com>
---
 drivers/gpu/drm/i915/spi/intel_spi_drv.c | 36 ++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/i915/spi/intel_spi_drv.c b/drivers/gpu/drm/i915/spi/intel_spi_drv.c
index 39369a0c64a0..22b804ebadc0 100644
--- a/drivers/gpu/drm/i915/spi/intel_spi_drv.c
+++ b/drivers/gpu/drm/i915/spi/intel_spi_drv.c
@@ -14,6 +14,7 @@
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/delay.h>
 #include "spi/intel_spi.h"
+#include "i915_reg_defs.h"
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
@@ -232,6 +233,24 @@ static ssize_t spi_write(struct i915_spi *spi, u8 region,
 		len_s -= to_shift;
 	}
 
+	if (!IS_ALIGNED(to, sizeof(u64)) &&
+	    ((to ^ (to + len_s)) & REG_GENMASK(31, 10))) {
+		/*
+		 * Workaround reads/writes across 1k-aligned addresses
+		 * (start u32 before 1k, end u32 after)
+		 * as this fails on hardware.
+		 */
+		u32 data;
+
+		memcpy(&data, &buf[0], sizeof(u32));
+		spi_write32(spi, to, data);
+		if (spi_error(spi))
+			return -EIO;
+		buf += sizeof(u32);
+		to += sizeof(u32);
+		len_s -= sizeof(u32);
+	}
+
 	len8 = ALIGN_DOWN(len_s, sizeof(u64));
 	for (i = 0; i < len8; i += sizeof(u64)) {
 		u64 data;
@@ -290,6 +309,23 @@ static ssize_t spi_read(struct i915_spi *spi, u8 region,
 		from += from_shift;
 	}
 
+	if (!IS_ALIGNED(from, sizeof(u64)) &&
+	    ((from ^ (from + len_s)) & REG_GENMASK(31, 10))) {
+		/*
+		 * Workaround reads/writes across 1k-aligned addresses
+		 * (start u32 before 1k, end u32 after)
+		 * as this fails on hardware.
+		 */
+		u32 data = spi_read32(spi, from);
+
+		if (spi_error(spi))
+			return -EIO;
+		memcpy(&buf[0], &data, sizeof(data));
+		len_s -= sizeof(u32);
+		buf += sizeof(u32);
+		from += sizeof(u32);
+	}
+
 	len8 = ALIGN_DOWN(len_s, sizeof(u64));
 	for (i = 0; i < len8; i += sizeof(u64)) {
 		u64 data = spi_read64(spi, from + i);
-- 
2.34.1