04.02.2020 15:02, Jon Hunter пишет:
>
> On 02/02/2020 22:28, Dmitry Osipenko wrote:
>> There is no harm in keeping DMA active in the case of error condition,
>> which should never happen in practice anyways. This will become useful
>> for the next patch, which will keep RPM enabled only during of DMA
>> transfer, and thus, it will be much nicer if cyclic DMA handler could
>> not touch the DMA-enable state.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>> ---
>> drivers/dma/tegra20-apb-dma.c | 9 +++++----
>> 1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>> index c7dc27ef1856..50abce608318 100644
>> --- a/drivers/dma/tegra20-apb-dma.c
>> +++ b/drivers/dma/tegra20-apb-dma.c
>> @@ -571,9 +571,7 @@ static bool handle_continuous_head_request(struct tegra_dma_channel *tdc,
>> */
>> hsgreq = list_first_entry(&tdc->pending_sg_req, typeof(*hsgreq), node);
>> if (!hsgreq->configured) {
>> - tegra_dma_stop(tdc);
>> - dev_err(tdc2dev(tdc), "Error in DMA transfer, aborting DMA\n");
>> - tegra_dma_abort_all(tdc);
>> + dev_err_ratelimited(tdc2dev(tdc), "Error in DMA transfer\n");
>
> While we are at it, a more descriptive error message could be good here.
> I believe that this condition would indicate a potential underrun condition.
Yes, this error indicates the underrun and indeed the error message
could be improved. I'll change it in v8.
>> return false;
>> }
>>
>> @@ -772,7 +770,10 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
>> if (!list_empty(&tdc->pending_sg_req) && was_busy) {
>> sgreq = list_first_entry(&tdc->pending_sg_req, typeof(*sgreq),
>> node);
>> - sgreq->dma_desc->bytes_transferred +=
>> + dma_desc = sgreq->dma_desc;
>> +
>> + if (dma_desc->dma_status != DMA_ERROR)
>> + dma_desc->bytes_transferred +=
>> get_current_xferred_count(tdc, sgreq, wcount);
>
> I am wondering if we need to check this here? I assume that the transfer
> count would still reflect the amount of data transferred, even if some
> was dropped. We will never know how much data was lost.
I'm wondering too.. stopping DMA in a error case removes this ambiguity
and that's why in my previous answer to v6 I suggested to drop this patch.
Do you think it's worth to keep this patch?
