Re: [PATCH v5 4/4] mmc: host: sdhci: Add a variable to defer to complete data requests if needed

[Baolin Wang]

On Wed, 6 Nov 2019 at 20:02, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 6/11/19 12:48 PM, Baolin Wang wrote:
> > On Wed, 6 Nov 2019 at 18:10, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> >>
> >> On 29/10/19 7:43 AM, Baolin Wang wrote:
> >>> When using the host software queue, it will trigger the next request in
> >>> irq handler without a context switch. But the sdhci_request() can not be
> >>> called in interrupt context when using host software queue for some host
> >>> drivers, due to the get_cd() ops can be sleepable.
> >>>
> >>> But for some host drivers, such as Spreadtrum host driver, the card is
> >>> nonremovable, so the get_cd() ops is not sleepable, which means we can
> >>> complete the data request and trigger the next request in irq handler
> >>> to remove the context switch for the Spreadtrum host driver.
> >>>
> >>> Thus we still need introduce a variable in struct sdhci_host to indicate
> >>> that we will always to defer to complete data requests if the sdhci_request()
> >>> can not be called in interrupt context for some host drivers, when using
> >>> the host software queue.
> >>>
> >>> Suggested-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> >>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
> >>> ---
> >>>  drivers/mmc/host/sdhci.c |    2 +-
> >>>  drivers/mmc/host/sdhci.h |    1 +
> >>>  2 files changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> >>> index 850241f..9cf2130 100644
> >>> --- a/drivers/mmc/host/sdhci.c
> >>> +++ b/drivers/mmc/host/sdhci.c
> >>> @@ -3035,7 +3035,7 @@ static inline bool sdhci_defer_done(struct sdhci_host *host,
> >>>  {
> >>>       struct mmc_data *data = mrq->data;
> >>>
> >>> -     return host->pending_reset ||
> >>> +     return host->pending_reset || (host->always_defer_done && data) ||
>
> To move ahead in the meantime without a new host API, just defer always i.e.

OK.

And I'll wait for a while to see if Ulf will post some comments for
this patch set before new version. Thanks.

>
> +     return host->pending_reset || host->always_defer_done ||
>
> >>
> >> I didn't realize you still wanted to call the request function in interrupt
> >> context.  In my view that needs a new host API
> >> i.e. int (*request_atomic)(struct mmc_host *mmc, struct mmc_request *mrq)
> >
> > Actually there are no documentation said that the
> > mmc_host_ops->request() is a sleepable API, so I introduce a
> > host->always_defer_done flag to decide if the request can be called in
> > interrupt context or not, since for some host drivers, the request()
> > implementation can be called in interrupt context.
> >
> > Yes, I agree a new host API is more reasonable, if you do not like the
> > current approach, I can add new patches to introduce the new
> > request_atomic() API. But can I create another separate patch set to
> > do this? since in this patch set, the Spreadtrum host driver's
> > request() implementation can be called in interrupt context. Or you
> > still want these changes introducing new request_atomic() can be done
> > in this patch set? Thanks.
> >
> >>
> >>>              ((host->flags & SDHCI_REQ_USE_DMA) && data &&
> >>>               data->host_cookie == COOKIE_MAPPED);
> >>>  }
> >>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> >>> index d89cdb9..38fbd18 100644
> >>> --- a/drivers/mmc/host/sdhci.h
> >>> +++ b/drivers/mmc/host/sdhci.h
> >>> @@ -533,6 +533,7 @@ struct sdhci_host {
> >>>       bool pending_reset;     /* Cmd/data reset is pending */
> >>>       bool irq_wake_enabled;  /* IRQ wakeup is enabled */
> >>>       bool v4_mode;           /* Host Version 4 Enable */
> >>> +     bool always_defer_done; /* Always defer to complete data requests */
> >>>
> >>>       struct mmc_request *mrqs_done[SDHCI_MAX_MRQS];  /* Requests done */
> >>>       struct mmc_command *cmd;        /* Current command */
> >>>
> >>
> >
> >
>


-- 
Baolin Wang
Best Regards