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authorPeter Ujfalusi <peter.ujfalusi@nokia.com>2010-10-11 14:18:56 -0700
committerTony Lindgren <tony@atomide.com>2010-10-11 14:18:56 -0700
commit0e4905c0199d683497833be60a428c784d7575b8 (patch)
tree943933b19b9e3f1a0340d044d544c6c3db4c6d67
parent3e57f1626b5febe5cc99aa6870377deef3ae03cc (diff)
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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 <peter.ujfalusi@nokia.com> Acked-by: Jarkko Nikula <jhnikula@gmail.com> Acked-by : Santosh Shilimkar <santosh.shilimkar@ti.com> Acked-by : Manjunath Kondaiah G <manjugk@ti.com> Signed-off-by: Tony Lindgren <tony@atomide.com>
-rw-r--r--arch/arm/plat-omap/dma.c36
-rw-r--r--arch/arm/plat-omap/include/plat/dma.h3
2 files changed, 37 insertions, 2 deletions
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index 420cef370b3..f5c5b8da9a8 100644
--- a/arch/arm/plat-omap/dma.c
+++ b/arch/arm/plat-omap/dma.c
@@ -30,6 +30,7 @@
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/slab.h>
+#include <linux/delay.h>
#include <asm/system.h>
#include <mach/hardware.h>
@@ -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;
diff --git a/arch/arm/plat-omap/include/plat/dma.h b/arch/arm/plat-omap/include/plat/dma.h
index 6f70f7cfe91..0cce4ca83aa 100644
--- a/arch/arm/plat-omap/include/plat/dma.h
+++ b/arch/arm/plat-omap/include/plat/dma.h
@@ -337,6 +337,9 @@
#define OMAP2_DMA_MISALIGNED_ERR_IRQ (1 << 11)
#define OMAP_DMA_CCR_EN (1 << 7)
+#define OMAP_DMA_CCR_RD_ACTIVE (1 << 9)
+#define OMAP_DMA_CCR_WR_ACTIVE (1 << 10)
+#define OMAP_DMA_CCR_SEL_SRC_DST_SYNC (1 << 24)
#define OMAP_DMA_CCR_BUFFERING_DISABLE (1 << 25)
#define OMAP_DMA_DATA_TYPE_S8 0x00