On Thu, May 8, 2014 at 2:42 AM, Yuvaraj Kumar <yuvaraj.cd@xxxxxxxxx> wrote:
> Any comments on this patch?
>
I'll just add that without this fix, running the tuning loop for UHS
modes is not reliable on dw_mmc because errors will happen and you
will eventually hit this race and hang. This can happen any time
there is tuning like during boot or during resume from suspend.
> On Thu, Mar 27, 2014 at 11:48 AM, Yuvaraj Kumar C D
> <yuvaraj.cd@xxxxxxxxx> wrote:
>> From: Doug Anderson <dianders@xxxxxxxxxxxx>
>>
>> If we happened to get a data error at just the wrong time the dw_mmc
>> driver could get into a state where it would never complete its
>> request. That would leave the caller just hanging there.
>>
>> We fix this two ways and both of the two fixes on their own appear to
>> fix the problems we've seen:
>>
>> 1. Fix a race in the tasklet where the interrupt setting the data
>> error happens _just after_ we check for it, then we get a
>> EVENT_XFER_COMPLETE. We fix this by repeating a bit of code.
>> 2. Fix it so that if we detect that we've got an error in the "data
>> busy" state and we're not going to do anything else we end the
>> request and unblock anyone waiting.
>>
>> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
>> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@xxxxxxxxx>
>> ---
>> drivers/mmc/host/dw_mmc.c | 47 +++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 47 insertions(+)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 1d77431..4c589f1 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -1300,6 +1300,14 @@ static void dw_mci_tasklet_func(unsigned long priv)
>> /* fall through */
>>
>> case STATE_SENDING_DATA:
>> + /*
>> + * We could get a data error and never a transfer
>> + * complete so we'd better check for it here.
>> + *
>> + * Note that we don't really care if we also got a
>> + * transfer complete; stopping the DMA and sending an
>> + * abort won't hurt.
>> + */
>> if (test_and_clear_bit(EVENT_DATA_ERROR,
>> &host->pending_events)) {
>> dw_mci_stop_dma(host);
>> @@ -1313,7 +1321,29 @@ static void dw_mci_tasklet_func(unsigned long priv)
>> break;
>>
>> set_bit(EVENT_XFER_COMPLETE, &host->completed_events);
>> +
>> + /*
>> + * Handle an EVENT_DATA_ERROR that might have shown up
>> + * before the transfer completed. This might not have
>> + * been caught by the check above because the interrupt
>> + * could have gone off between the previous check and
>> + * the check for transfer complete.
>> + *
>> + * Technically this ought not be needed assuming we
>> + * get a DATA_COMPLETE eventually (we'll notice the
>> + * error and end the request), but it shouldn't hurt.
>> + *
>> + * This has the advantage of sending the stop command.
>> + */
>> + if (test_and_clear_bit(EVENT_DATA_ERROR,
>> + &host->pending_events)) {
>> + dw_mci_stop_dma(host);
>> + send_stop_abort(host, data);
>> + state = STATE_DATA_ERROR;
>> + break;
>> + }
>> prev_state = state = STATE_DATA_BUSY;
>> +
>> /* fall through */
>>
>> case STATE_DATA_BUSY:
>> @@ -1336,6 +1366,23 @@ static void dw_mci_tasklet_func(unsigned long priv)
>> /* stop command for open-ended transfer*/
>> if (data->stop)
>> send_stop_abort(host, data);
>> + } else {
>> + /*
>> + * If we don't have a command complete now we'll
>> + * never get one since we just reset everything;
>> + * better end the request.
>> + *
>> + * If we do have a command complete we'll fall
>> + * through to the SENDING_STOP command and
>> + * everything will be peachy keen.
>> + *
>> + * TODO: I guess we shouldn't send a stop?
>> + */
>> + if (!test_bit(EVENT_CMD_COMPLETE,
>> + &host->pending_events)) {
>> + dw_mci_request_end(host, mrq);
>> + goto unlock;
>> + }
>> }
>>
>> /*
>> --
>> 1.7.10.4
>>
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