6.17-stable review patch. If anyone has any objections, please let me know.
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From: Arnd Bergmann arnd@arndb.de
[ Upstream commit d6ddd9beb1a5c32acb9b80f5c2cd8b17f41371d1 ]
Short MMIO transfers that are not a multiple of four bytes in size need a special case for the final bytes, however the existing implementation is not endian-safe and introduces an incorrect byteswap on big-endian kernels.
This usually does not cause problems because most systems are little-endian and most transfers are multiple of four bytes long, but still needs to be fixed to avoid the extra byteswap.
Change the special case for both i3c_writel_fifo() and i3c_readl_fifo() to use non-byteswapping writesl() and readsl() with a single element instead of the byteswapping writel()/readl() that are meant for individual MMIO registers. As data is copied between a FIFO and a memory buffer, the writesl()/readsl() loops are typically based on __raw_readl()/ __raw_writel(), resulting in the order of bytes in the FIFO to match the order in the buffer, regardless of the CPU endianess.
The earlier versions in the dw-i3c and i3c-master-cdns had a correct implementation, but the generic version that was recently added broke it.
Fixes: 733b439375b4 ("i3c: master: Add inline i3c_readl_fifo() and i3c_writel_fifo()") Cc: Manikanta Guntupalli manikanta.guntupalli@amd.com Signed-off-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Jorge Marques jorge.marques@analog.com Link: https://lore.kernel.org/r/20250924201837.3691486-1-arnd@kernel.org Signed-off-by: Alexandre Belloni alexandre.belloni@bootlin.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/i3c/internals.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h index 0d857cc68cc5d..79ceaa5f5afd6 100644 --- a/drivers/i3c/internals.h +++ b/drivers/i3c/internals.h @@ -38,7 +38,11 @@ static inline void i3c_writel_fifo(void __iomem *addr, const void *buf, u32 tmp = 0;
memcpy(&tmp, buf + (nbytes & ~3), nbytes & 3); - writel(tmp, addr); + /* + * writesl() instead of writel() to keep FIFO + * byteorder on big-endian targets + */ + writesl(addr, &tmp, 1); } }
@@ -55,7 +59,11 @@ static inline void i3c_readl_fifo(const void __iomem *addr, void *buf, if (nbytes & 3) { u32 tmp;
- tmp = readl(addr); + /* + * readsl() instead of readl() to keep FIFO + * byteorder on big-endian targets + */ + readsl(addr, &tmp, 1); memcpy(buf + (nbytes & ~3), &tmp, nbytes & 3); } }