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dmaengine: stm32-dma: avoid 64-bit division in stm32_dma_get_max_width

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[ Upstream commit 2498363310e9b5e5de0e104709adc35c9f3ff7d9 ]

Using the % operator on a 64-bit variable is expensive and can
cause a link failure:

arm-linux-gnueabi-ld: drivers/dma/stm32-dma.o: in function `stm32_dma_get_max_width':
stm32-dma.c:(.text+0x170): undefined reference to `__aeabi_uldivmod'
arm-linux-gnueabi-ld: drivers/dma/stm32-dma.o: in function `stm32_dma_set_xfer_param':
stm32-dma.c:(.text+0x1cd4): undefined reference to `__aeabi_uldivmod'

As we know that we just want to check the alignment in
stm32_dma_get_max_width(), there is no need for a full division, and
using a simple mask is a faster replacement.

Same in stm32_dma_set_xfer_param(), change this to only allow burst
transfers if the address is a multiple of the length.
stm32_dma_get_best_burst just after will take buf_len into account to fix
burst in case of misalignment.

Fixes: b20fd5fa310c ("dmaengine: stm32-dma: fix stm32_dma_get_max_width")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20211103153312.41483-1-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Arnd Bergmann 2021-11-03 16:33:12 +01:00 committed by Greg Kroah-Hartman
parent 4ee1ac7f3c
commit 0bf8323e2c
1 changed files with 3 additions and 3 deletions
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6
drivers/dma/stm32-dma.c
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@ -280,7 +280,7 @@ static enum dma_slave_buswidth stm32_dma_get_max_width(u32 buf_len,
max_width > DMA_SLAVE_BUSWIDTH_1_BYTE)
max_width = max_width >> 1;
if (buf_addr % max_width)
if (buf_addr & (max_width - 1))
max_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
return max_width;
@ -756,7 +756,7 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
* Set memory burst size - burst not possible if address is not aligned on
* the address boundary equal to the size of the transfer
*/
if (buf_addr % buf_len)
if (buf_addr & (buf_len - 1))
src_maxburst = 1;
else
src_maxburst = STM32_DMA_MAX_BURST;
@ -812,7 +812,7 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
* Set memory burst size - burst not possible if address is not aligned on
* the address boundary equal to the size of the transfer
*/
if (buf_addr % buf_len)
if (buf_addr & (buf_len - 1))
dst_maxburst = 1;
else
dst_maxburst = STM32_DMA_MAX_BURST;