RE: [PATCH v2] mmc: dw_mmc: Make sure we don't get stuck when we get an error

Seungwon Jeon
2014-07-27T14:15:12Z

Hi Chris & Ulf,

I hope you find this patch for next.

Thanks,
Seungwon Jeon

On Wed, May 21, 2014, Seungwon Jeon wrote:
> On Wed, May 21, 2014, Doug Anderson wrote:
> > 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@chromium.org>
> > Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@gmail.com>
>
> It will be applied after "mmc: dw_mmc: change to use recommended reset procedure"
>
> Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
>
> Thanks,
> Seungwon Jeon
>
> > ---
> > Changes in v2:
> > - Removed TODO
> > - Set cmd to NULL before calling dw_mci_request_end()
> >
> > drivers/mmc/host/dw_mmc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 46 insertions(+)
> >
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index cced599..54ec8b0 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -1318,6 +1318,14 @@ 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);
> > @@ -1331,7 +1339,29 @@ 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:
> > @@ -1354,6 +1384,22 @@ 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.
> > + */
> > + if (!test_bit(EVENT_CMD_COMPLETE,
> > + &host->pending_events)) {
> > + host->cmd = NULL;
> > + dw_mci_request_end(host, mrq);
> > + goto unlock;
> > + }
> > }
> >
> > /*
> > --
> > 1.9.1.423.g4596e3a
> >
> > --
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