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

On 06/11/2019, Baolin Wang <baolin.wang@linaro.org> wrote:
> On Wed, 6 Nov 2019 at 20:02, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 6/11/19 12:48 PM, Baolin Wang wrote:
>> > On Wed, 6 Nov 2019 at 18:10, Adrian Hunter <adrian.hunter@intel.com>
>> > 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@intel.com>
>> >>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> >>> ---
>> >>> 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.

Before new version, I want to make things clear in case I
misunderstood your points, so you mean I should set always_defer_done
= true for our Spreadtrum host driver in this patch? Or just like
below patch? Thanks.

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 850241f..4bef066 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 ||
((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..a73ce89 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 requests */

struct mmc_request *mrqs_done[SDHCI_MAX_MRQS]; /* Requests done */
struct mmc_command *cmd; /* Current command */
> 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
>


--
Baolin Wang
Best Regards

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