From 3e57f1626b5febe5cc99aa6870377deef3ae03cc Mon Sep 17 00:00:00 2001 From: Jarkko Nikula Date: Mon, 11 Oct 2010 14:18:45 -0700 Subject: omap: dma: Fix buffering disable bit setting for omap24xx An errata workaround for omap24xx is not setting the buffering disable bit 25 what is the purpose but channel enable bit 7 instead. Background for this fix is the DMA stalling issue with ASoC omap-mcbsp driver. Peter Ujfalusi has found an issue in recording that the DMA stall could happen if there were a buffer overrun detected by ALSA and the DMA was stopped and restarted due that. This problem is known to occur on both OMAP2420 and OMAP3. It can recover on OMAP3 after dma free, dma request and reconfiguration cycle. However, on OMAP2420 it seems that only way to recover is a reset. Problem was not visible before the commit c12abc0. That commit changed that the McBSP transmitter/receiver is released from reset only when needed. That is, only enabled McBSP transmitter without transmission was able to prevent this DMA stall problem in receiving side and underlying problem did not show up until now. McBSP transmitter itself seems to no be reason since DMA stall does not recover by enabling the transmission after stall. Debugging showed that there were a DMA write active during DMA stop time and it never completed even when restarting the DMA. Experimenting showed that the DMA buffering disable bit could be used to avoid stalling when using source synchronized transfers. However that could have performance hit and OMAP3 TRM states that buffering disable is not allowed for destination synchronized transfers so subsequent patch will implement a method to complete DMA writes when stopping. This patch is based on assumtion that complete lock-up on OMAP2420 is different but related problem. I don't have access to OMAP2420 errata but I believe this old workaround here is put for a reason but unfortunately a wrong bit was typed and problem showed up only now. Signed-off-by: Jarkko Nikula Signed-off-by: Peter Ujfalusi Acked-by: Manjunath Kondaiah G Signed-off-by: Tony Lindgren --- arch/arm/plat-omap/dma.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'arch/arm/plat-omap/dma.c') diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index ec7eddf9e525..420cef370b33 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -996,11 +996,17 @@ void omap_start_dma(int lch) l = dma_read(CCR(lch)); /* - * Errata: On ES2.0 BUFFERING disable must be set. - * This will always fail on ES1.0 + * Errata: Inter Frame DMA buffering issue (All OMAP2420 and + * OMAP2430ES1.0): DMA will wrongly buffer elements if packing and + * bursting is enabled. This might result in data gets stalled in + * FIFO at the end of the block. + * Workaround: DMA channels must have BUFFERING_DISABLED bit set to + * guarantee no data will stay in the DMA FIFO in case inter frame + * buffering occurs. */ - if (cpu_is_omap24xx()) - l |= OMAP_DMA_CCR_EN; + if (cpu_is_omap2420() || + (cpu_is_omap2430() && (omap_type() == OMAP2430_REV_ES1_0))) + l |= OMAP_DMA_CCR_BUFFERING_DISABLE; l |= OMAP_DMA_CCR_EN; dma_write(l, CCR(lch)); -- cgit v1.2.2 From 0e4905c0199d683497833be60a428c784d7575b8 Mon Sep 17 00:00:00 2001 From: Peter Ujfalusi Date: Mon, 11 Oct 2010 14:18:56 -0700 Subject: OMAP3: DMA: Errata i541: sDMA FIFO draining does not finish Implement the suggested workaround for OMAP3 regarding to sDMA draining issue, when the channel is disabled on the fly. This errata affects the following configuration: sDMA transfer is source synchronized Buffering is enabled SmartStandby is selected. The issue can be easily reproduced by creating overrun situation while recording audio. Either introduce load to the CPU: nice -19 arecord -D hw:0 -M -B 10000 -F 5000 -f dat > /dev/null & \ dd if=/dev/urandom of=/dev/null or suspending the arecord, and resuming it: arecord -D hw:0 -M -B 10000 -F 5000 -f dat > /dev/null CTRL+Z; fg; CTRL+Z; fg; ... In case of overrun audio stops DMA, and restarts it (without reseting the sDMA channel). When we hit this errata in stop case (sDMA drain did not complete), at the coming start the sDMA will not going to be operational (it is still draining). This leads to DMA stall condition. On OMAP3 we can recover with sDMA channel reset, it has been observed that by introducing unrelated sDMA activity might also help (reading from MMC for example). The same errata exists for OMAP2, where the suggestion is to disable the buffering to avoid this type of error. On OMAP3 the suggestion is to set sDMA to NoStandby before disabling the channel, and wait for the drain to finish, than configure sDMA to SmartStandby again. Signed-off-by: Peter Ujfalusi Acked-by: Jarkko Nikula Acked-by : Santosh Shilimkar Acked-by : Manjunath Kondaiah G Signed-off-by: Tony Lindgren --- arch/arm/plat-omap/dma.c | 36 ++++++++++++++++++++++++++++++++++-- 1 file changed, 34 insertions(+), 2 deletions(-) (limited to 'arch/arm/plat-omap/dma.c') diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index 420cef370b33..f5c5b8da9a87 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include @@ -1024,8 +1025,39 @@ void omap_stop_dma(int lch) dma_write(0, CICR(lch)); l = dma_read(CCR(lch)); - l &= ~OMAP_DMA_CCR_EN; - dma_write(l, CCR(lch)); + /* OMAP3 Errata i541: sDMA FIFO draining does not finish */ + if (cpu_is_omap34xx() && (l & OMAP_DMA_CCR_SEL_SRC_DST_SYNC)) { + int i = 0; + u32 sys_cf; + + /* Configure No-Standby */ + l = dma_read(OCP_SYSCONFIG); + sys_cf = l; + l &= ~DMA_SYSCONFIG_MIDLEMODE_MASK; + l |= DMA_SYSCONFIG_MIDLEMODE(DMA_IDLEMODE_NO_IDLE); + dma_write(l , OCP_SYSCONFIG); + + l = dma_read(CCR(lch)); + l &= ~OMAP_DMA_CCR_EN; + dma_write(l, CCR(lch)); + + /* Wait for sDMA FIFO drain */ + l = dma_read(CCR(lch)); + while (i < 100 && (l & (OMAP_DMA_CCR_RD_ACTIVE | + OMAP_DMA_CCR_WR_ACTIVE))) { + udelay(5); + i++; + l = dma_read(CCR(lch)); + } + if (i >= 100) + printk(KERN_ERR "DMA drain did not complete on " + "lch %d\n", lch); + /* Restore OCP_SYSCONFIG */ + dma_write(sys_cf, OCP_SYSCONFIG); + } else { + l &= ~OMAP_DMA_CCR_EN; + dma_write(l, CCR(lch)); + } if (!omap_dma_in_1510_mode() && dma_chan[lch].next_lch != -1) { int next_lch, cur_lch = lch; -- cgit v1.2.2