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Date: Fri, 11 Jan 2013 11:39:36 -0800
From: merez@...eaurora.org
To: "Ulf Hansson" <ulf.hansson@...aro.org>
Cc: merez@...eaurora.org, linux-mmc@...r.kernel.org,
linux-arm-msm@...r.kernel.org,
"open list" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] mmc: core: Add support for idle time BKOPS
Thanks, Ulf. Your help is appreciated.
> On 10 January 2013 10:22, <merez@...eaurora.org> wrote:
>> Hi Ulf,
>>
>> See below.
>>
>> Thanks,
>> Maya
>>> Hi Maya,
>>>
>>> On 24 December 2012 14:51, Maya Erez <merez@...eaurora.org> 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 can be set by the
>>>> host
>>>> controller. If this time is not set, a default time is used.
>>>
>>> I believe I have asked this question before; Have you considered to
>>> use runtime PM autosuspend feature instead of adding a delayed work to
>>> handle idle BKOPS?
>>> Similar how sdio is doing mmc_power_save|restore, but for sd/mmc we
>>> handle the BKOPS instead. My feeling is that it could simplify this
>>> patch quite significantly.
>>>
>>> It would be interesting to hear about your view of this idea.
>>
>> Sorry for not responding to this idea earlier.
>> As I am not familiar enough with runtime suspend it's hard for me to
>> specify if this can work or not. Can you please point me to the function
>> which handles the autosuspend that you think could be a good candidate
>> for
>> doing the BKOPS check.
>> Lately we encountered many issues regarding BKOPS and had to change the
>> implementation. I will upload a new patch soon (still with the delayed
>> work usage) and we can continue the discussion on the new patch.
>>
>
> I will take the liberty to put together a kind of a skeleton patch for
> how we could make use of runtime PM for this kind of features that is
> supposed to be executed in the background. You can then base your
> patches on top of that, I think that could be a way forward.
>
> In the meanwhile I will continue to follow up on your Idle BKOPS patches.
>
>>>
>>>> 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@...eaurora.org>
>>>>
>>>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>>>> index 21056b9..64bbf75 100644
>>>> --- a/drivers/mmc/card/block.c
>>>> +++ b/drivers/mmc/card/block.c
>>>> @@ -1473,9 +1473,15 @@ 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 aaed768..36cef94 100644
>>>> --- a/drivers/mmc/core/core.c
>>>> +++ b/drivers/mmc/core/core.c
>>>> @@ -256,6 +256,33 @@ 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
>>>> @@ -272,25 +299,47 @@ 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;
>>>> @@ -319,6 +368,27 @@ out:
>>>> }
>>>> EXPORT_SYMBOL(mmc_start_bkops);
>>>>
>>>> +/**
>>>> + * 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);
>>>> @@ -585,6 +655,17 @@ 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);
>>>>
>>>> /*
>>>> @@ -596,6 +677,7 @@ int mmc_stop_bkops(struct mmc_card *card)
>>>> err = 0;
>>>> }
>>>>
>>>> +out:
>>>> return err;
>>>> }
>>>> EXPORT_SYMBOL(mmc_stop_bkops);
>>>> @@ -2536,15 +2618,15 @@ 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 e6e3911..f68624a 100644
>>>> --- a/drivers/mmc/core/mmc.c
>>>> +++ b/drivers/mmc/core/mmc.c
>>>> @@ -1275,6 +1275,26 @@ 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);
>>>> +
>>>> + /*
>>>> + * Calculate the time to start the BKOPs
>>>> checking.
>>>> + * The host controller can set this time in
>>>> order to
>>>> + * prevent a race condition before starting
>>>> BKOPs
>>>> + * and going into suspend.
>>>> + * If the host controller didn't set this
>>>> time,
>>>> + * a default value is used.
>>>> + */
>>>> + card->bkops_info.delay_ms =
>>>> MMC_IDLE_BKOPS_TIME_MS;
>>>> + if (card->bkops_info.host_delay_ms)
>>>> + card->bkops_info.delay_ms =
>>>> +
>>>> card->bkops_info.host_delay_ms;
>>>> + }
>>>> + }
>>>> +
>>>> if (!oldcard)
>>>> host->card = card;
>>>>
>>>> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
>>>> index 5c69315..ca4cf19 100644
>>>> --- a/include/linux/mmc/card.h
>>>> +++ b/include/linux/mmc/card.h
>>>> @@ -210,6 +210,30 @@ struct mmc_part {
>>>> #define MMC_BLK_DATA_AREA_RPMB (1<<3)
>>>> };
>>>>
>>>> +/**
>>>> + * struct mmc_bkops_info - BKOPS data
>>>> + * @dw: Idle time bkops delayed work
>>>> + * @host_delay_ms: The host controller time to start bkops
>>>> + * @delay_ms: The time to start the BKOPS
>>>> + * delayed work once MMC thread is idle
>>>> + * @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
>>>> + */
>>>> +struct mmc_bkops_info {
>>>> + struct delayed_work dw;
>>>> + unsigned int host_delay_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
>>>> + bool cancel_delayed_work;
>>>> + bool started_delayed_bkops;
>>>> +};
>>>> +
>>>> /*
>>>> * MMC device
>>>> */
>>>> @@ -278,6 +302,8 @@ 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 5bf7c22..c6426c6 100644
>>>> --- a/include/linux/mmc/core.h
>>>> +++ b/include/linux/mmc/core.h
>>>> @@ -145,6 +145,8 @@ 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 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
>>>> --
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>>>> Please read the FAQ at http://www.tux.org/lkml/
>>>
>>> Kind regards
>>> Ulf Hansson
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
>>> the body of a message to majordomo@...r.kernel.org
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>>>
>>
>>
>
> Kind regards
> Ulf Hansson
>
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