Hi,
On Fri, Oct 01, 2010 at 01:04:55PM +0200, ext Peter Ujfalusi wrote:
> 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@xxxxxxxxx>
> ---
> arch/arm/plat-omap/dma.c | 35 +++++++++++++++++++++++++++++++-
> arch/arm/plat-omap/include/plat/dma.h | 3 ++
> 2 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
> index 7115884..287a00e 100644
> --- a/arch/arm/plat-omap/dma.c
> +++ b/arch/arm/plat-omap/dma.c
[snip]
> + l = sys_cf = dma_read(OCP_SYSCONFIG);
Shouldn't it be avoided?
Regards,
David
> + 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 completed 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 776ba44..cf66f85 100644
> --- a/arch/arm/plat-omap/include/plat/dma.h
> +++ b/arch/arm/plat-omap/include/plat/dma.h
> @@ -335,6 +335,9 @@
> #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
> --
> 1.7.3
>
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