[PATCH] mtd: spear_smi: Fix nonalignment not handled in memcpy_toio

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Any write with either dd or flashcp to a device driven by the
spear_smi.c driver will pass through the spear_smi_cpy_toio()
function. This function will get called for chunks of up to 256 bytes.
If the amount of data is smaller, we may have a problem if the data
length is not 4-byte aligned. In this situation, the kernel panics
during the memcpy:

    # dd if=/dev/urandom bs=1001 count=1 of=/dev/mtd6
    spear_smi_cpy_toio [620] dest c9070000, src c7be8800, len 256
    spear_smi_cpy_toio [620] dest c9070100, src c7be8900, len 256
    spear_smi_cpy_toio [620] dest c9070200, src c7be8a00, len 256
    spear_smi_cpy_toio [620] dest c9070300, src c7be8b00, len 233
    Unhandled fault: external abort on non-linefetch (0x808) at 0xc90703e8
    [...]
    PC is at memcpy+0xcc/0x330

Workaround this issue by using the alternate _memcpy_toio() method
which at least does not present the same problem.

Fixes: f18dbbb1bfe0 ("mtd: ST SPEAr: Add SMI driver for serial NOR flash")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---

Hello,

This patch could not be tested with a mainline kernel (only compiled)
but was tested with a stable 4.14.x kernel. I have really no idea why
memcpy fails in this situation that's why I propose this workaround
but I bet there is something deeper not working.

Thanks,
Miquèl

 drivers/mtd/devices/spear_smi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/spear_smi.c b/drivers/mtd/devices/spear_smi.c
index 986f81d2f93e..d888625a3244 100644
--- a/drivers/mtd/devices/spear_smi.c
+++ b/drivers/mtd/devices/spear_smi.c
@@ -614,7 +614,7 @@ static inline int spear_smi_cpy_toio(struct spear_smi *dev, u32 bank,
 	ctrlreg1 = readl(dev->io_base + SMI_CR1);
 	writel((ctrlreg1 | WB_MODE) & ~SW_MODE, dev->io_base + SMI_CR1);
 
-	memcpy_toio(dest, src, len);
+	_memcpy_toio(dest, src, len);
 
 	writel(ctrlreg1, dev->io_base + SMI_CR1);
 
-- 
2.20.1


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