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Subject[PATCH AUTOSEL 4.14 22/35] mtd: spi-nor: Fix Cadence QSPI page fault kernel panic
Date
From: Thor Thayer <thor.thayer@linux.intel.com>

[ Upstream commit a6a66f80c85e8e20573ca03fabf32445954a88d5 ]

The current Cadence QSPI driver caused a kernel panic sporadically
when writing to QSPI. The problem was caused by writing more bytes
than needed because the QSPI operated on 4 bytes at a time.
<snip>
[ 11.202044] Unable to handle kernel paging request at virtual address bffd3000
[ 11.209254] pgd = e463054d
[ 11.211948] [bffd3000] *pgd=2fffb811, *pte=00000000, *ppte=00000000
[ 11.218202] Internal error: Oops: 7 [#1] SMP ARM
[ 11.222797] Modules linked in:
[ 11.225844] CPU: 1 PID: 1317 Comm: systemd-hwdb Not tainted 4.17.7-d0c45cd44a8f
[ 11.235796] Hardware name: Altera SOCFPGA Arria10
[ 11.240487] PC is at __raw_writesl+0x70/0xd4
[ 11.244741] LR is at cqspi_write+0x1a0/0x2cc
</snip>
On a page boundary limit the number of bytes copied from the tx buffer
to remain within the page.

This patch uses a temporary buffer to hold the 4 bytes to write and then
copies only the bytes required from the tx buffer.

Reported-by: Adrian Amborzewicz <adrian.ambrozewicz@intel.com>
Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/mtd/spi-nor/cadence-quadspi.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
index 8d89204b90d2..f22dd34f4f83 100644
--- a/drivers/mtd/spi-nor/cadence-quadspi.c
+++ b/drivers/mtd/spi-nor/cadence-quadspi.c
@@ -625,9 +625,23 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
reg_base + CQSPI_REG_INDIRECTWR);

while (remaining > 0) {
+ size_t write_words, mod_bytes;
+
write_bytes = remaining > page_size ? page_size : remaining;
- iowrite32_rep(cqspi->ahb_base, txbuf,
- DIV_ROUND_UP(write_bytes, 4));
+ write_words = write_bytes / 4;
+ mod_bytes = write_bytes % 4;
+ /* Write 4 bytes at a time then single bytes. */
+ if (write_words) {
+ iowrite32_rep(cqspi->ahb_base, txbuf, write_words);
+ txbuf += (write_words * 4);
+ }
+ if (mod_bytes) {
+ unsigned int temp = 0xFFFFFFFF;
+
+ memcpy(&temp, txbuf, mod_bytes);
+ iowrite32(temp, cqspi->ahb_base);
+ txbuf += mod_bytes;
+ }

ret = wait_for_completion_timeout(&cqspi->transfer_complete,
msecs_to_jiffies
@@ -638,7 +652,6 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
goto failwr;
}

- txbuf += write_bytes;
remaining -= write_bytes;

if (remaining > 0)
--
2.17.1
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