linux-kernel - Re: [PATCH v3 3/4] mmc: host: hsq: Handle an unusual case of returing busy

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Date:   Fri, 3 Apr 2020 09:21:19 +0800
From:   Baolin Wang <baolin.wang7@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] mmc: host: hsq: Handle an unusual case of returing busy

Hi Adrian,

On Thu, Apr 2, 2020 at 6:45 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> On 19/03/20 12:54 pm, Baolin Wang wrote:
> > There is an unusual case that the card is busy when trying to send a
> > command, and we can not polling the card status in interrupt context
> > by using request_atomic() to dispatch requests.
> >
> > Thus we should queue a work to try again in the non-atomic context
> > in case the host releases the busy signal later.
>
> I think this should be part of patch 1

OK. Will move these changes into patch 1.

>
> >
> > Signed-off-by: Baolin Wang <baolin.wang7@...il.com>
>
> Sorry for the slow reply.
>
> > ---
> >  drivers/mmc/host/mmc_hsq.c | 37 ++++++++++++++++++++++++++++++++++++-
> >  drivers/mmc/host/mmc_hsq.h |  1 +
> >  2 files changed, 37 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
> > index fdbaa98..3edad11 100644
> > --- a/drivers/mmc/host/mmc_hsq.c
> > +++ b/drivers/mmc/host/mmc_hsq.c
> > @@ -15,11 +15,33 @@
> >  #define HSQ_NUM_SLOTS        64
> >  #define HSQ_INVALID_TAG      HSQ_NUM_SLOTS
> >
> > +static void mmc_hsq_retry_handler(struct work_struct *work)
> > +{
> > +     struct mmc_hsq *hsq = container_of(work, struct mmc_hsq, retry_work);
> > +     struct mmc_host *mmc = hsq->mmc;
> > +     struct mmc_request *mrq = hsq->mrq;
> > +     struct mmc_data *data = mrq->data;
> > +
> > +     if (mmc->ops->request) {
>
> ->request() is not an optional mmc operation so checking it is not necessary.

Yes, will remove the checking.

>
> > +             mmc->ops->request(mmc, mrq);
> > +             return;
> > +     }
> > +
> > +     /*
> > +      * If host does not supply the callback in normal context to
> > +      * handle request, just finish this request.
> > +      */
> > +     data->error = -EBUSY;
> > +     data->bytes_xfered = 0;
> > +     mmc_hsq_finalize_request(mmc, mrq);
> > +}
> > +
> >  static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
> >  {
> >       struct mmc_host *mmc = hsq->mmc;
> >       struct hsq_slot *slot;
> >       unsigned long flags;
> > +     int ret = 0;
> >
> >       spin_lock_irqsave(&hsq->lock, flags);
> >
> > @@ -42,9 +64,21 @@ static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
> >       spin_unlock_irqrestore(&hsq->lock, flags);
> >
> >       if (mmc->ops->request_atomic)
> > -             mmc->ops->request_atomic(mmc, hsq->mrq);
> > +             ret = mmc->ops->request_atomic(mmc, hsq->mrq);
> >       else
> >               mmc->ops->request(mmc, hsq->mrq);
> > +
> > +     /*
> > +      * If returning BUSY from request_atomic(), which means the card
> > +      * may be busy now, and we should change to non-atomic context to
> > +      * try again for this unusual case, to avoid time-consuming operations
> > +      * in the atomic context.
> > +      *
> > +      * Note: we can ignore other error cases, since the host driver
> > +      * will handle them.
> > +      */
> > +     if (ret == -EBUSY)
> > +             schedule_work(&hsq->retry_work);
>
> Let's add a warning for unexpected return values i.e.
>
>         WARN_ON_ONCE(ret && ret != -EBUSY);

Sure. Thanks for your comments.

>
>
> >  }
> >
> >  static void mmc_hsq_update_next_tag(struct mmc_hsq *hsq, int remains)
> > @@ -327,6 +361,7 @@ int mmc_hsq_init(struct mmc_hsq *hsq, struct mmc_host *mmc)
> >       hsq->mmc->cqe_private = hsq;
> >       mmc->cqe_ops = &mmc_hsq_ops;
> >
> > +     INIT_WORK(&hsq->retry_work, mmc_hsq_retry_handler);
> >       spin_lock_init(&hsq->lock);
> >       init_waitqueue_head(&hsq->wait_queue);
> >
> > diff --git a/drivers/mmc/host/mmc_hsq.h b/drivers/mmc/host/mmc_hsq.h
> > index d51beb7..81f6c4f 100644
> > --- a/drivers/mmc/host/mmc_hsq.h
> > +++ b/drivers/mmc/host/mmc_hsq.h
> > @@ -12,6 +12,7 @@ struct mmc_hsq {
> >       wait_queue_head_t wait_queue;
> >       struct hsq_slot *slot;
> >       spinlock_t lock;
> > +     struct work_struct retry_work;
> >
> >       int next_tag;
> >       int num_slots;
> >
>


-- 
Baolin Wang