On Tuesday, October 11, 2016 13:13 CEST, Nandor Han <nandor.han@xxxxxx> wrote: > The residue calculation was taking in consideration that dma > transaction status will be always retrieved in the dma callback > used to inform that dma transfer is complete. However this is not > the case for all subsystems that use dma. Some subsystems use a > timer to check the dma status periodically. > > Therefore the calculation was updated and residue is calculated > accordingly by a) update the residue calculation taking in > consideration the last used buffer index by using *buf_ptail* variable > and b) chn_real_count (number of bytes transferred) is initialized to > zero, when dma channel is created, to avoid using an uninitialized > value in residue calculation when dma status is checked without > waiting dma complete event. The previous patch* apparently introduced an issue that was detectable when using the fsl_ssi audio driver that produced non smooth audio output. This patch fix the issue. I tested this patch by booting it in two different devices and checked that the sound issues related to fsl_ssi driver were fixed. * - https://patchwork.kernel.org/patch/9268463/ > > Signed-off-by: Nandor Han <nandor.han@xxxxxx> Acked-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx> Tested-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx> > --- > drivers/dma/imx-sdma.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index b9629b2..d1651a5 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -298,6 +298,7 @@ struct sdma_engine; > * @event_id1 for channels that use 2 events > * @word_size peripheral access size > * @buf_tail ID of the buffer that was processed > + * @buf_ptail ID of the previous buffer that was processed > * @num_bd max NUM_BD. number of descriptors currently handling > */ > struct sdma_channel { > @@ -309,6 +310,7 @@ struct sdma_channel { > unsigned int event_id1; > enum dma_slave_buswidth word_size; > unsigned int buf_tail; > + unsigned int buf_ptail; > unsigned int num_bd; > unsigned int period_len; > struct sdma_buffer_descriptor *bd; > @@ -700,6 +702,8 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac) > sdmac->chn_real_count = bd->mode.count; > bd->mode.status |= BD_DONE; > bd->mode.count = sdmac->period_len; > + sdmac->buf_ptail = sdmac->buf_tail; > + sdmac->buf_tail = (sdmac->buf_tail + 1) % sdmac->num_bd; > > /* > * The callback is called from the interrupt context in order > @@ -710,9 +714,6 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac) > > dmaengine_desc_get_callback_invoke(&sdmac->desc, NULL); > > - sdmac->buf_tail++; > - sdmac->buf_tail %= sdmac->num_bd; > - > if (error) > sdmac->status = old_status; > } > @@ -1186,6 +1187,8 @@ static struct dma_async_tx_descriptor *sdma_prep_slave_sg( > sdmac->flags = 0; > > sdmac->buf_tail = 0; > + sdmac->buf_ptail = 0; > + sdmac->chn_real_count = 0; > > dev_dbg(sdma->dev, "setting up %d entries for channel %d.\n", > sg_len, channel); > @@ -1288,6 +1291,8 @@ static struct dma_async_tx_descriptor *sdma_prep_dma_cyclic( > sdmac->status = DMA_IN_PROGRESS; > > sdmac->buf_tail = 0; > + sdmac->buf_ptail = 0; > + sdmac->chn_real_count = 0; > sdmac->period_len = period_len; > > sdmac->flags |= IMX_DMA_SG_LOOP; > @@ -1385,7 +1390,7 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan, > u32 residue; > > if (sdmac->flags & IMX_DMA_SG_LOOP) > - residue = (sdmac->num_bd - sdmac->buf_tail) * > + residue = (sdmac->num_bd - sdmac->buf_ptail) * > sdmac->period_len - sdmac->chn_real_count; > else > residue = sdmac->chn_count - sdmac->chn_real_count; > -- > 2.7.1 > -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
