dmaengine: at_hdmac: remove clear-on-read in atc_dostart()
Subsystems (2)
PATCH 1/1 dmaengine: at_hdmac: remove clear-on-read in atc_dostart()
This loop on EBCISR register was designed to clear IRQ sources before enabling a DMA channel. This register is clear-on-read so a race condition can appear if another channel is already active and has just finished its transfer. Removing this read on EBCISR is fixing the issue as there is no case where an IRQ could be pending: we already make sure that this register is drained at probe() time and during resume.
--- drivers/dma/at_hdmac.c | 4 ---- 1 file changed, 4 deletions(-)
drivers/dma/at_hdmac.c +0 -4
@@ -221,10 +221,6 @@ static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)vdbg_dump_regs (atchan); -/* clear any pending interrupt */ -while (dma_readl (atdma,EBCISR )) -cpu_relax (); -channel_writel (atchan,SADDR ,0 );channel_writel (atchan,DADDR ,0 );channel_writel (atchan,CTRLA ,0 );
Signature · 1 line
1.7.10
PATCH 1/1 dmaengine: at_hdmac: remove clear-on-read in atc_dostart()
On 04/16/2012 02:46 PM, Nicolas Ferre :
Quoted 9 lines
This loop on EBCISR register was designed to clear IRQ sources before enabling a DMA channel. This register is clear-on-read so a race condition can appear if another channel is already active and has just finished its transfer. Removing this read on EBCISR is fixing the issue as there is no case where an IRQ could be pending: we already make sure that this register is drained at
probe()time and during resume.Signed-off-by Nicolas Ferre <[email protected]>Cc stable <[email protected]>
Vinod,
Could you please take this patch as a fix for 3.4-rc?
Thanks, best regards,
Quoted 19 lines
--- drivers/dma/at_hdmac.c | 4 ---- 1 file changed, 4 deletions(-)drivers/dma/at_hdmac.c +0
-4@@ -221,10 +221,6 @@ static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)vdbg_dump_regs (atchan); -/* clear any pending interrupt */ -while (dma_readl (atdma,EBCISR )) -cpu_relax (); -channel_writel (atchan,SADDR ,0 );channel_writel (atchan,DADDR ,0 );channel_writel (atchan,CTRLA ,0 );
Signature · 1 line
Nicolas Ferre
PATCH 1/1 dmaengine: at_hdmac: remove clear-on-read in atc_dostart()
In reply to Nicolas FerreQuoted 9 lines · Nicolas Ferre
This loop on EBCISR register was designed to clear IRQ sources before enabling a DMA channel. This register is clear-on-read so a race condition can appear if another channel is already active and has just finished its transfer. Removing this read on EBCISR is fixing the issue as there is no case where an IRQ could be pending: we already make sure that this register is drained at
probe()time and during resume.Signed-off-by Nicolas Ferre <[email protected]>Cc stable <[email protected]>
Applied thanks.
Quoted 19 lines
--- drivers/dma/at_hdmac.c | 4 ---- 1 file changed, 4 deletions(-)drivers/dma/at_hdmac.c +0
-4@@ -221,10 +221,6 @@ static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)vdbg_dump_regs (atchan); -/* clear any pending interrupt */ -while (dma_readl (atdma,EBCISR )) -cpu_relax (); -channel_writel (atchan,SADDR ,0 );channel_writel (atchan,DADDR ,0 );channel_writel (atchan,CTRLA ,0 );
Signature · 1 line
~Vinod