Hi Chris,
I managed to find a solution in which there is no need to check the number
of written / discarded sectors as a trigger for BKOPS status check.
I moved the code that checks the need to stop the BKOPS to mmc/block code,
in which there is no need for additional claim_host and remove_host
operations.
Please review this patch.
Thanks,
Maya
On Sun, November 25, 2012 3:56 am, Maya Erez wrote:
> Devices have various maintenance operations need to perform internally.
> In order to reduce latencies during time critical operations like read
> and write, it is better to execute maintenance operations in other
> times - when the host is not being serviced. Such operations are called
> Background operations (BKOPS).
> The device notifies the status of the BKOPS need by updating BKOPS_STATUS
> (EXT_CSD byte [246]).
>
> According to the standard a host that supports BKOPS shall check the
> status periodically and start background operations as needed, so that
> the device has enough time for its maintenance operations.
>
> This patch adds support for this periodic check of the BKOPS status.
> Since foreground operations are of higher priority than background
> operations the host will check the need for BKOPS when it is idle,
> and in case of an incoming request the BKOPS operation will be
> interrupted.
>
> When the mmcqd thread is idle, a delayed work is created to check the
> need for BKOPS. The time to start the delayed work is calculated based
> on the host controller suspend timeout, in case it was set. If not, a
> default time is used.
> If BKOPS are required in level 1, which is non-blocking, there will be
> polling of the card status to wait for the BKOPS completion and prevent
> suspend that will interrupt the BKOPS.
> If the card raised an exception, the need for urgent BKOPS (level 2/3)
> will be checked immediately and if needed, the BKOPS will be performed
> without waiting for the next idle time.
>
> Signed-off-by: Maya Erez <merez@xxxxxxxxxxxxxx>
>
> ---
> This patch is based on the periodic BKOPS implementation in version 8 of
> "support BKOPS feature for eMMC" patch.
> The patch was modified to answer the following issues:
> - In order to prevent a race condition between going into suspend and
> starting BKOPS,
> the suspend timeout of the host controller is taking into accound in
> determination of the start time
> of the delayed work
> - Since mmc_start_bkops is called from two contexts now, mmc_claim_host
> was moved to the beginning of the function
> - Also, the check of doing_bkops should be protected when determing if an
> HPI is needed due to the same reason.
>
> Changes in v3:
> - Move the call to stop_bkops to block.c.
> This allows us to remove the mmc_claim_host from inside the function
> and doesn't cause additional degradation
> due to un-neccessary calim host operation
>
> Changes in v2:
> - Check the number of written / discarded sectors as the trigger for
> checking the BKOPS need.
> - Code review fixes
>
> ---
> drivers/mmc/card/block.c | 8 ++-
> drivers/mmc/card/queue.c | 2 +
> drivers/mmc/core/core.c | 178
> +++++++++++++++++++++++++++++++++++++++++++---
> drivers/mmc/core/mmc.c | 23 ++++++
> include/linux/mmc/card.h | 35 +++++++++
> include/linux/mmc/core.h | 3 +
> 6 files changed, 237 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 172a768..40b4ae3 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -1394,9 +1394,15 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq,
> struct request *req)
> struct mmc_blk_data *md = mq->data;
> struct mmc_card *card = md->queue.card;
>
> - if (req && !mq->mqrq_prev->req)
> + if (req && !mq->mqrq_prev->req) {
> /* claim host only for the first request */
> mmc_claim_host(card->host);
> + if (card->ext_csd.bkops_en &&
> + card->bkops_info.started_delayed_bkops) {
> + card->bkops_info.started_delayed_bkops = false;
> + mmc_stop_bkops(card);
> + }
> + }
>
> ret = mmc_blk_part_switch(card, md);
> if (ret) {
> diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
> index fadf52e..9d0c96a 100644
> --- a/drivers/mmc/card/queue.c
> +++ b/drivers/mmc/card/queue.c
> @@ -51,6 +51,7 @@ static int mmc_queue_thread(void *d)
> {
> struct mmc_queue *mq = d;
> struct request_queue *q = mq->queue;
> + struct mmc_card *card = mq->card;
>
> current->flags |= PF_MEMALLOC;
>
> @@ -83,6 +84,7 @@ static int mmc_queue_thread(void *d)
> set_current_state(TASK_RUNNING);
> break;
> }
> + mmc_start_delayed_bkops(card);
> up(&mq->thread_sem);
> schedule();
> down(&mq->thread_sem);
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 06c42cf..72ae15b 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -253,9 +253,36 @@ mmc_start_request(struct mmc_host *host, struct
> mmc_request *mrq)
> }
>
> /**
> + * mmc_start_delayed_bkops() - Start a delayed work to check for
> + * the need of non urgent BKOPS
> + *
> + * @card: MMC card to start BKOPS on
> + */
> +void mmc_start_delayed_bkops(struct mmc_card *card)
> +{
> + if (!card || !card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
> + return;
> +
> + pr_debug("%s: %s: queueing delayed_bkops_work\n",
> + mmc_hostname(card->host), __func__);
> +
> + /*
> + * cancel_delayed_bkops_work will prevent a race condition between
> + * fetching a request by the mmcqd and the delayed work, in case
> + * it was removed from the queue work but not started yet
> + */
> + card->bkops_info.cancel_delayed_work = false;
> + card->bkops_info.started_delayed_bkops = true;
> + queue_delayed_work(system_nrt_wq, &card->bkops_info.dw,
> + msecs_to_jiffies(
> + card->bkops_info.delay_ms));
> +}
> +EXPORT_SYMBOL(mmc_start_delayed_bkops);
> +
> +/**
> * mmc_start_bkops - start BKOPS for supported cards
> * @card: MMC card to start BKOPS
> - * @form_exception: A flag to indicate if this function was
> + * @from_exception: A flag to indicate if this function was
> * called due to an exception raised by the card
> *
> * Start background operations whenever requested.
> @@ -269,25 +296,47 @@ void mmc_start_bkops(struct mmc_card *card, bool
> from_exception)
> bool use_busy_signal;
>
> BUG_ON(!card);
> -
> - if (!card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
> + if (!card->ext_csd.bkops_en)
> return;
>
> + mmc_claim_host(card->host);
> +
> + if ((card->bkops_info.cancel_delayed_work) && !from_exception) {
> + pr_debug("%s: %s: cancel_delayed_work was set, exit\n",
> + mmc_hostname(card->host), __func__);
> + card->bkops_info.cancel_delayed_work = false;
> + goto out;
> + }
> +
> + if (mmc_card_doing_bkops(card)) {
> + pr_debug("%s: %s: already doing bkops, exit\n",
> + mmc_hostname(card->host), __func__);
> + goto out;
> + }
> +
> err = mmc_read_bkops_status(card);
> if (err) {
> pr_err("%s: Failed to read bkops status: %d\n",
> mmc_hostname(card->host), err);
> - return;
> + goto out;
> }
>
> if (!card->ext_csd.raw_bkops_status)
> - return;
> + goto out;
>
> + pr_info("%s: %s: card->ext_csd.raw_bkops_status = 0x%x\n",
> + mmc_hostname(card->host), __func__,
> + card->ext_csd.raw_bkops_status);
> +
> + /*
> + * If the function was called due to exception but there is no need
> + * for urgent BKOPS, BKOPs will be performed by the delayed BKOPs
> + * work, before going to suspend
> + */
> if (card->ext_csd.raw_bkops_status < EXT_CSD_BKOPS_LEVEL_2 &&
> from_exception)
> - return;
> + goto out;
>
> - mmc_claim_host(card->host);
> if (card->ext_csd.raw_bkops_status >= EXT_CSD_BKOPS_LEVEL_2) {
> timeout = MMC_BKOPS_MAX_TIMEOUT;
> use_busy_signal = true;
> @@ -309,13 +358,108 @@ void mmc_start_bkops(struct mmc_card *card, bool
> from_exception)
> * bkops executed synchronously, otherwise
> * the operation is in progress
> */
> - if (!use_busy_signal)
> + if (!use_busy_signal) {
> mmc_card_set_doing_bkops(card);
> + pr_debug("%s: %s: starting the polling thread\n",
> + mmc_hostname(card->host), __func__);
> + queue_work(system_nrt_wq,
> + &card->bkops_info.poll_for_completion);
> + }
> +
> out:
> mmc_release_host(card->host);
> }
> EXPORT_SYMBOL(mmc_start_bkops);
>
> +/**
> + * mmc_bkops_completion_polling() - Poll on the card status to
> + * wait for the non-blocking BKOPS completion
> + * @work: The completion polling work
> + *
> + * The on-going reading of the card status will prevent the card
> + * from getting into suspend while it is in the middle of
> + * performing BKOPS.
> + * Since the non blocking BKOPS can be interrupted by a fetched
> + * request we also check IF mmc_card_doing_bkops in each
> + * iteration.
> + */
> +void mmc_bkops_completion_polling(struct work_struct *work)
> +{
> + struct mmc_card *card = container_of(work, struct mmc_card,
> + bkops_info.poll_for_completion);
> + unsigned long timeout_jiffies = jiffies +
> + msecs_to_jiffies(BKOPS_COMPLETION_POLLING_TIMEOUT_MS);
> + u32 status;
> + int err;
> +
> + /*
> + * Wait for the BKOPs to complete. Keep reading the status to prevent
> + * the host from getting into suspend
> + */
> + do {
> + mmc_claim_host(card->host);
> +
> + if (!mmc_card_doing_bkops(card))
> + goto out;
> +
> + err = mmc_send_status(card, &status);
> + if (err) {
> + pr_err("%s: error %d requesting status\n",
> + mmc_hostname(card->host), err);
> + goto out;
> + }
> +
> + /*
> + * Some cards mishandle the status bits, so make sure to check
> + * both the busy indication and the card state.
> + */
> + if ((status & R1_READY_FOR_DATA) &&
> + (R1_CURRENT_STATE(status) != R1_STATE_PRG)) {
> + pr_debug("%s: %s: completed BKOPs, exit polling\n",
> + mmc_hostname(card->host), __func__);
> + mmc_card_clr_doing_bkops(card);
> + card->bkops_info.started_delayed_bkops = false;
> + goto out;
> + }
> +
> + mmc_release_host(card->host);
> +
> + /*
> + * Sleep before checking the card status again to allow the
> + * card to complete the BKOPs operation
> + */
> + msleep(BKOPS_COMPLETION_POLLING_INTERVAL_MS);
> + } while (time_before(jiffies, timeout_jiffies));
> +
> + pr_err("%s: %s: exit polling due to timeout\n",
> + mmc_hostname(card->host), __func__);
> +
> + return;
> +out:
> + mmc_release_host(card->host);
> +}
> +
> +/**
> + * mmc_start_idle_time_bkops() - check if a non urgent BKOPS is
> + * needed
> + * @work: The idle time BKOPS work
> + */
> +void mmc_start_idle_time_bkops(struct work_struct *work)
> +{
> + struct mmc_card *card = container_of(work, struct mmc_card,
> + bkops_info.dw.work);
> +
> + /*
> + * Prevent a race condition between mmc_stop_bkops and the delayed
> + * BKOPS work in case the delayed work is executed on another CPU
> + */
> + if (card->bkops_info.cancel_delayed_work)
> + return;
> +
> + mmc_start_bkops(card, false);
> +}
> +EXPORT_SYMBOL(mmc_start_idle_time_bkops);
> +
> static void mmc_wait_done(struct mmc_request *mrq)
> {
> complete(&mrq->completion);
> @@ -582,6 +726,17 @@ int mmc_stop_bkops(struct mmc_card *card)
> int err = 0;
>
> BUG_ON(!card);
> +
> + /*
> + * Notify the delayed work to be cancelled, in case it was already
> + * removed from the queue, but was not started yet
> + */
> + card->bkops_info.cancel_delayed_work = true;
> + if (delayed_work_pending(&card->bkops_info.dw))
> + cancel_delayed_work_sync(&card->bkops_info.dw);
> + if (!mmc_card_doing_bkops(card))
> + goto out;
> +
> err = mmc_interrupt_hpi(card);
>
> /*
> @@ -593,6 +748,7 @@ int mmc_stop_bkops(struct mmc_card *card)
> err = 0;
> }
>
> +out:
> return err;
> }
> EXPORT_SYMBOL(mmc_stop_bkops);
> @@ -2506,15 +2662,15 @@ int mmc_pm_notify(struct notifier_block
> *notify_block,
> switch (mode) {
> case PM_HIBERNATION_PREPARE:
> case PM_SUSPEND_PREPARE:
> - if (host->card && mmc_card_mmc(host->card) &&
> - mmc_card_doing_bkops(host->card)) {
> + if (host->card && mmc_card_mmc(host->card)) {
> + mmc_claim_host(host);
> err = mmc_stop_bkops(host->card);
> + mmc_release_host(host);
> if (err) {
> pr_err("%s: didn't stop bkops\n",
> mmc_hostname(host));
> return err;
> }
> - mmc_card_clr_doing_bkops(host->card);
> }
>
> spin_lock_irqsave(&host->lock, flags);
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 7cc4638..dba76e3 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1258,6 +1258,29 @@ static int mmc_init_card(struct mmc_host *host, u32
> ocr,
> }
> }
>
> + if (!oldcard) {
> + if (card->ext_csd.bkops_en) {
> + INIT_DELAYED_WORK(&card->bkops_info.dw,
> + mmc_start_idle_time_bkops);
> + INIT_WORK(&card->bkops_info.poll_for_completion,
> + mmc_bkops_completion_polling);
> +
> + /*
> + * Calculate the time to start the BKOPs checking.
> + * The idle time of the host controller should be taken
> + * into account in order to prevent a race condition
> + * before starting BKOPs and going into suspend.
> + * If the host controller didn't set its idle time,
> + * a default value is used.
> + */
> + card->bkops_info.delay_ms = MMC_IDLE_BKOPS_TIME_MS;
> + if (card->bkops_info.host_suspend_tout_ms)
> + card->bkops_info.delay_ms = min(
> + card->bkops_info.delay_ms,
> + card->bkops_info.host_suspend_tout_ms/2);
> + }
> + }
> +
> if (!oldcard)
> host->card = card;
>
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 943550d..224e2a5 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -208,6 +208,39 @@ struct mmc_part {
> #define MMC_BLK_DATA_AREA_GP (1<<2)
> };
>
> +/**
> + * struct mmc_bkops_info - BKOPS data
> + * @dw: Idle time bkops delayed work
> + * @host_suspend_tout_ms: The host controller idle time,
> + * before getting into suspend
> + * @delay_ms: The time to start the BKOPS
> + * delayed work once MMC thread is idle
> + * @poll_for_completion: Poll on BKOPS completion
> + * @cancel_delayed_work: A flag to indicate if the delayed work
> + * should be cancelled
> + * @started_delayed_bkops: A flag to indicate if the delayed
> + * work was scheduled
> + * @sectors_changed: number of sectors written or
> + * discard since the last idle BKOPS were scheduled
> + */
> +struct mmc_bkops_info {
> + struct delayed_work dw;
> + unsigned int host_suspend_tout_ms;
> + unsigned int delay_ms;
> +/*
> + * A default time for checking the need for non urgent BKOPS once mmcqd
> + * is idle.
> + */
> +#define MMC_IDLE_BKOPS_TIME_MS 2000
> + struct work_struct poll_for_completion;
> +/* Polling timeout and interval for waiting on non-blocking BKOPs
> completion */
> +#define BKOPS_COMPLETION_POLLING_TIMEOUT_MS 10000 /* in ms */
> +#define BKOPS_COMPLETION_POLLING_INTERVAL_MS 1000 /* in ms */
> + bool cancel_delayed_work;
> + bool started_delayed_bkops;
> + unsigned int sectors_changed;
> +};
> +
> /*
> * MMC device
> */
> @@ -276,6 +309,8 @@ struct mmc_card {
> struct dentry *debugfs_root;
> struct mmc_part part[MMC_NUM_PHY_PARTITION]; /* physical partitions */
> unsigned int nr_parts;
> +
> + struct mmc_bkops_info bkops_info;
> };
>
> /*
> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
> index 9b9cdaf..665d345 100644
> --- a/include/linux/mmc/core.h
> +++ b/include/linux/mmc/core.h
> @@ -145,6 +145,9 @@ extern int mmc_app_cmd(struct mmc_host *, struct
> mmc_card *);
> extern int mmc_wait_for_app_cmd(struct mmc_host *, struct mmc_card *,
> struct mmc_command *, int);
> extern void mmc_start_bkops(struct mmc_card *card, bool from_exception);
> +extern void mmc_start_delayed_bkops(struct mmc_card *card);
> +extern void mmc_start_idle_time_bkops(struct work_struct *work);
> +extern void mmc_bkops_completion_polling(struct work_struct *work);
> extern int __mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int,
> bool);
> extern int mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int);
>
> --
> 1.7.3.3
> --
> QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
