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

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Date:   Thu, 2 Apr 2020 13:45:03 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Baolin Wang <baolin.wang7@...il.com>, ulf.hansson@...aro.org
Cc:     orsonzhai@...il.com, zhang.lyra@...il.com, arnd@...db.de,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] mmc: host: hsq: Handle an unusual case of returing
 busy

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

> 
> 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.

> +		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);


>  }
>  
>  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;
>