From: Amelie Delaunay <amelie.delaunay@foss.st.com> To: Vinod Koul <vkoul@kernel.org>, Maxime Coquelin <mcoquelin.stm32@gmail.com>, Alexandre Torgue <alexandre.torgue@foss.st.com> Cc: <dmaengine@vger.kernel.org>, <linux-stm32@st-md-mailman.stormreply.com>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>, Amelie Delaunay <amelie.delaunay@foss.st.com>, Arnd Bergmann <arnd@arndb.de>, kernel test robot <lkp@intel.com> Subject: [PATCH 1/1] dmaengine: stm32-dma: avoid 64-bit division in stm32_dma_get_max_width Date: Wed, 3 Nov 2021 16:33:12 +0100 [thread overview] Message-ID: <20211103153312.41483-1-amelie.delaunay@foss.st.com> (raw) From: Arnd Bergmann <arnd@arndb.de> 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> --- drivers/dma/stm32-dma.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c index 2283c500f4ce..83a37a6955a3 100644 --- a/drivers/dma/stm32-dma.c +++ b/drivers/dma/stm32-dma.c @@ -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; @@ -757,7 +757,7 @@ 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; @@ -813,7 +813,7 @@ 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; -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Amelie Delaunay <amelie.delaunay@foss.st.com> To: Vinod Koul <vkoul@kernel.org>, Maxime Coquelin <mcoquelin.stm32@gmail.com>, Alexandre Torgue <alexandre.torgue@foss.st.com> Cc: <dmaengine@vger.kernel.org>, <linux-stm32@st-md-mailman.stormreply.com>, <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>, Amelie Delaunay <amelie.delaunay@foss.st.com>, Arnd Bergmann <arnd@arndb.de>, kernel test robot <lkp@intel.com> Subject: [PATCH 1/1] dmaengine: stm32-dma: avoid 64-bit division in stm32_dma_get_max_width Date: Wed, 3 Nov 2021 16:33:12 +0100 [thread overview] Message-ID: <20211103153312.41483-1-amelie.delaunay@foss.st.com> (raw) From: Arnd Bergmann <arnd@arndb.de> 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> --- drivers/dma/stm32-dma.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c index 2283c500f4ce..83a37a6955a3 100644 --- a/drivers/dma/stm32-dma.c +++ b/drivers/dma/stm32-dma.c @@ -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; @@ -757,7 +757,7 @@ 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; @@ -813,7 +813,7 @@ 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; -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2021-11-03 15:33 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-03 15:33 Amelie Delaunay [this message] 2021-11-03 15:33 ` [PATCH 1/1] dmaengine: stm32-dma: avoid 64-bit division in stm32_dma_get_max_width Amelie Delaunay 2021-11-09 5:50 ` Vinod Koul 2021-11-09 5:50 ` Vinod Koul
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