> -----Original Message----- > From: linux-omap-owner@xxxxxxxxxxxxxxx [mailto:linux-omap- > owner@xxxxxxxxxxxxxxx] On Behalf Of Peter Ujfalusi > Sent: Friday, October 01, 2010 6:06 PM > To: Tony Lindgren > Cc: linux-omap@xxxxxxxxxxxxxxx; Jarkko Nikula; Liam Girdwood > Subject: [PATCH v3 2/2] OMAP3: DMA: Errata: 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). > Just fyi, FIFO drain errata is not applicable for OMAP4 SDMA IP version. Patch looks good to me. > 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> > Acked-by: Jarkko Nikula <jhnikula@xxxxxxxxx> Acked-by : Santosh Shilimkar <santosh.shilimkar@xxxxxx> > --- > arch/arm/plat-omap/dma.c | 36 > +++++++++++++++++++++++++++++++- > arch/arm/plat-omap/include/plat/dma.h | 3 ++ > 2 files changed, 37 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c > index 7115884..b298361 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> > @@ -1018,8 +1019,39 @@ 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 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
