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Message-ID: <CAPDyKFo4LVUSLY9=L3qG9caZuhrmie8WdD0vcyQi88L=HAbXjg@mail.gmail.com>
Date: Fri, 11 Jan 2013 13:51:41 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: merez@...eaurora.org
Cc: 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
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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>>
>> 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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