Re: [PATCH v8] mmc: support BKOPS feature for eMMC

[Jaehoon Chung <jh80.chung@samsung.com>]

On 05/11/2012 08:40 PM, S, Venkatraman wrote:

> On Thu, May 10, 2012 at 7:07 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> Enable eMMC background operations (BKOPS) feature.
>>
>> If URGENT_BKOPS is set after a response, note that BKOPS
>> are required. After all I/O requests are finished, run
>> BKOPS if required. Should read/write operations be requested
>> during BKOPS, first issue HPI to interrupt the ongoing BKOPS
>> and then service the request.
>> If BKOPS-STATUS is upper than LEVEL2, need to check until clear
>> the BKOPS-STATUS vaule.
>>
>> If you want to enable this feature, set MMC_CAP2_BKOPS.
>> And if you want to set the BKOPS_EN bit in ext_csd register,
>> use the MMC_CAP2_INIT_BKOPS.
>>
>> When BKOPS_STATUS is Level-3, if we're waiting for done, it spent 60~80sec.
>> So Added timeout value. if timeout value is set to 0, send hpi command.
>>
>> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>> ---
>> Changelog V8:
>>        - Remove host->lock spin lock reviewed by Adrian
>>        - Support periodic start bkops
>>        - when bkops_status is level-3, if timeout is set to 0, send hpi.
>>        - Move the start-bkops point
>> Changelog V7:
>>        - Use HPI command when issued URGENT_BKOPS
>>        - Recheck until clearing the bkops-status bit.
>> Changelog V6:
>>        - Add the flag of check-bkops-status.
>>          (For fixing async_req problem)
>>        - Add the capability for MMC_CAP2_INIT_BKOPS.
>>          (When unset the bkops_en bit in ext_csd register)
>>        - modify the wrong condition.
>> Changelog V5:
>>        - Rebase based on the latest mmc-next.
>>        - modify codes based-on Chris's comment
>> Changelog V4:
>>        - Add mmc_read_bkops_status
>>        - When URGENT_BKOPS(level2-3), didn't use HPI command.
>>        - In mmc_switch(), use R1B/R1 according to level.
>> Changelog V3:
>>        - move the bkops setting's location in mmc_blk_issue_rw_rq
>>        - modify condition checking
>>        - bkops_en is assigned ext_csd[EXT_CSD_BKOPS_EN] instead of "1"
>>        - remove the unused code
>>        - change pr_debug instead of pr_warn in mmc_send_hpi_cmd
>>        - Add the Future consideration suggested by Per
>> Changelog V2:
>>        - Use EXCEPTION_STATUS instead of URGENT_BKOPS
>>        - Add function to check Exception_status(for eMMC4.5)
>> ---
>>  drivers/mmc/card/queue.c   |    2 +
>>  drivers/mmc/core/core.c    |  170 +++++++++++++++++++++++++++++++++++++++++++-
>>  drivers/mmc/core/host.c    |    1 +
>>  drivers/mmc/core/mmc.c     |   18 +++++
>>  drivers/mmc/core/mmc_ops.c |    4 +
>>  include/linux/mmc/card.h   |   16 ++++
>>  include/linux/mmc/core.h   |    5 ++
>>  include/linux/mmc/host.h   |    4 +
>>  include/linux/mmc/mmc.h    |   20 +++++
>>  9 files changed, 238 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
>> index e360a97..e4a2cde 100644
>> --- a/drivers/mmc/card/queue.c
>> +++ b/drivers/mmc/card/queue.c
>> @@ -66,6 +66,8 @@ static int mmc_queue_thread(void *d)
>>                spin_unlock_irq(q->queue_lock);
>>
>>                if (req || mq->mqrq_prev->req) {
>> +                       if (mmc_card_doing_bkops(mq->card))
>> +                               mmc_stop_bkops(mq->card);
>>                        set_current_state(TASK_RUNNING);
>>                        mq->issue_fn(mq, req);
>>                } else {
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 0b6141d..91a03d5 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -175,6 +175,13 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
>>                if (mrq->done)
>>                        mrq->done(mrq);
>>
>> +               /*
>> +                * Check BKOPS urgency from each R1 response
>> +                */
>> +               if (host->card && mmc_card_mmc(host->card) &&
>> +                       (cmd->resp[0] & R1_EXCEPTION_EVENT))
>> +                       mmc_card_set_check_bkops(host->card);
>> +
>>                mmc_host_clk_release(host);
>>        }
>>  }
>> @@ -245,6 +252,76 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
>>        host->ops->request(host, mrq);
>>  }
>>
>> +static void mmc_send_bkops_cmd(struct mmc_card *card)
>> +{
>> +       int err;
>> +
>> +       BUG_ON(!card);
>> +
>> +       err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>> +                       EXT_CSD_BKOPS_START, 1, 0);
>> +       if (err) {
>> +               pr_warning("%s: error %d starting bkops\n",
>> +                          mmc_hostname(card->host), err);
>> +               mmc_card_clr_need_bkops(card);
>> +               return;
>> +       }
>> +
>> +       mmc_card_clr_need_bkops(card);
>> +       mmc_card_set_doing_bkops(card);
>> +
>> +}
>> +
>> +void mmc_start_periodic_bkops(struct work_struct *work)
> 
> There's nothing periodic about this function, by looking at the contents.
> Maybe this one should be called mmc_start_bkops ..

Well...i will checked this point..i tested with eMMC4.5 card...In my case, working this function.
But in your case, didn't work nothing..i will rework to this point after debugging.

> 
>> +{
>> +       struct mmc_host *host = container_of(work, struct mmc_host,
>> +                       start_bkops.work);
>> +
>> +       mmc_card_set_check_bkops(host->card);
> Why is this being set here. The condition should be in the caller context.
> 
>> +
>> +       mmc_claim_host(host);
>> +       mmc_start_bkops(host->card);
>> +       mmc_release_host(host);
>> +}
>> +EXPORT_SYMBOL(mmc_start_periodic_bkops);
>> +
>> +/**
>> + *     mmc_start_bkops - start BKOPS for supported cards
>> + *     @card: MMC card to start BKOPS
>> + *
>> + *     Start background operations whenever requested.
>> + *     when the urgent BKOPS bit is set in a R1 command response
>> + *     then background operations should be started immediately.
>> +*/
>> +void mmc_start_bkops(struct mmc_card *card)
> 
> .. and this one should be called __mmc_start_bkops() ?

Sure..i will change that.

> 
>> +{
>> +       BUG_ON(!card);
>> +       if (!card->ext_csd.bkops_en || !(card->host->caps2 & MMC_CAP2_BKOPS))
>> +               return;
>> +
>> +       if (mmc_card_check_bkops(card)) {
>> +               mmc_card_clr_check_bkops(card);
>> +               if (mmc_is_exception_event(card, EXT_CSD_URGENT_BKOPS)) {
>> +                       if (card->ext_csd.raw_bkops_status)
>> +                               mmc_card_set_need_bkops(card);
> 
> This breaks abstraction. Why check ext_csd even after URGENT_BKOPS is set ?

You means that need not to check ext_csd?
Well I didn't think so, we need to check bkops-status register

> 
>> +               } else
>> +                       mmc_card_clr_need_bkops(card);
>> +       }
>> +
>> +       /*
>> +        * If card_need_bkops_flag didn't set, then do nothing just
>> +        * return
>> +        */
>> +       if (mmc_card_doing_bkops(card) || !mmc_card_need_bkops(card))
>> +               goto check_bkops;
>> +
>> +       mmc_send_bkops_cmd(card);
>> +
>> +check_bkops:
>> +       queue_delayed_work(system_nrt_wq, &card->host->start_bkops, 5 * HZ);
> 
> IIUC, queue_delayed_work->start_bkops = mmc_start_periodic_bkops ->
> mmc_start_bkops -> queue_delayed_work
> .. ad infinitum ?

Actually, i want to get review for this point..How did you think about?

> 
>> +}
>> +EXPORT_SYMBOL(mmc_start_bkops);
>> +
>>  static void mmc_wait_done(struct mmc_request *mrq)
>>  {
>>        complete(&mrq->completion);
>> @@ -348,8 +425,10 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
>>        struct mmc_async_req *data = host->areq;
>>
>>        /* Prepare a new request */
>> -       if (areq)
>> +       if (areq) {
>> +               cancel_delayed_work_sync(&host->start_bkops);
>>                mmc_pre_req(host, areq->mrq, !host->areq);
>> +       }
>>
>>        if (host->areq) {
>>                mmc_wait_for_req_done(host, host->areq->mrq);
>> @@ -359,8 +438,11 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
>>        if (!err && areq)
>>                start_err = __mmc_start_req(host, areq->mrq);
>>
>> -       if (host->areq)
>> +       if (host->areq) {
>>                mmc_post_req(host, host->areq->mrq, 0);
>> +               if (!areq && host->areq && mmc_card_mmc(host->card))
>> +                       mmc_start_bkops(host->card);
>> +       }
>>
>>         /* Cancel a prepared request if it was not started. */
>>        if ((err || start_err) && areq)
>> @@ -480,6 +562,84 @@ int mmc_wait_for_cmd(struct mmc_host *host, struct mmc_command *cmd, int retries
>>  EXPORT_SYMBOL(mmc_wait_for_cmd);
>>
>>  /**
>> + *     mmc_stop_bkops - stop ongoing BKOPS
>> + *     @card: MMC card to check BKOPS
>> + *
>> + *     Send HPI command to interrupt ongoing background operations,
>> + *     to allow rapid servicing of foreground operations,e.g. read/
>> + *     writes. Wait until the card comes out of the programming state
>> + *     to avoid errors in servicing read/write requests.
>> + */
>> +int mmc_stop_bkops(struct mmc_card *card)
>> +{
>> +       int err = 0;
>> +       unsigned int timeout = 0x10000;
>> +       u32 status;
>> +
>> +       BUG_ON(!card);
>> +       cancel_delayed_work_sync(&card->host->start_bkops);
>> +
>> +       if (card->ext_csd.raw_bkops_status == EXT_CSD_BKOPS_LEVEL_3) {
>> +               do {
>> +                       if (timeout == 0)
>> +                               break;
>> +                       mmc_claim_host(card->host);
>> +                       mmc_send_status(card, &status);
>> +                       mmc_release_host(card->host);
>> +
>> +                       timeout--;
>> +               } while (R1_CURRENT_STATE(status) == R1_STATE_PRG);
>> +               if (timeout != 0)
>> +                       goto done;
>> +       }
> 
> This won't necessarily work all the time. Once BKOPS_START is issued, the card
> might finish GC and move to transfer state even before HPI can be sent.
> So just exit if the card is in transfer state already.

Right..But if didn't wait for prog-done, we can issue the HPI.
(If didn't use Busy waiting flag)

> 
> In this context, kdorfman's comments on "mmc:fix HPI execution
> sequence" makes sense.
> 
>> +
>> +       err = mmc_interrupt_hpi(card);
>> +
>> +done:
>> +       mmc_card_clr_doing_bkops(card);
>> +
>> +       return err;
>> +}
>> +EXPORT_SYMBOL(mmc_stop_bkops);
>> +
>> +int mmc_read_bkops_status(struct mmc_card *card)
>> +{
>> +       int err;
>> +       u8 ext_csd[512];
>> +
>> +       mmc_claim_host(card->host);
>> +       err = mmc_send_ext_csd(card, ext_csd);
>> +       mmc_release_host(card->host);
>> +       if (err)
>> +               return err;
>> +
>> +       card->ext_csd.raw_bkops_status = ext_csd[EXT_CSD_BKOPS_STATUS];
>> +       card->ext_csd.raw_exception_status = ext_csd[EXT_CSD_EXCEPTION_STATUS];
>> +
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL(mmc_read_bkops_status);
>> +
>> +int mmc_is_exception_event(struct mmc_card *card, unsigned int value)
>> +{
>> +       int err;
>> +
>> +       err = mmc_read_bkops_status(card);
>> +       if (err) {
>> +               pr_err("%s: Didn't read bkops status : %d\n",
>> +                      mmc_hostname(card->host), err);
>> +               return 0;
>> +       }
>> +
>> +       /* In eMMC 4.41, R1_EXCEPTION_EVENT is URGENT_BKOPS */
>> +       if (card->ext_csd.rev == 5)
>> +               return 1;
> 
> Please swap the order in which you are doing this.
> For eMMC4.41, we can save the mmc_read_bkops_status atleast for 4.41 card
> for _every_ request, which is not used.

If card is eMMC4.41, how did you check bkops-status?
In eMCM4.41, also check the bkops-status level.

> 
>> +
>> +       return (card->ext_csd.raw_exception_status & value) ? 1 : 0;
>> +}
>> +EXPORT_SYMBOL(mmc_is_exception_event);
>> +
>> +/**
>>  *     mmc_set_data_timeout - set the timeout for a data command
>>  *     @data: data phase for command
>>  *     @card: the MMC card associated with the data transfer
>> @@ -2382,6 +2542,12 @@ 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)) {
>> +                       mmc_interrupt_hpi(host->card);
>> +                       mmc_card_clr_doing_bkops(host->card);
>> +               }
>> +               cancel_delayed_work_sync(&host->start_bkops);
>>
>>                spin_lock_irqsave(&host->lock, flags);
>>                host->rescan_disable = 1;
>> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
>> index 91c84c7..3b6a8e4 100644
>> --- a/drivers/mmc/core/host.c
>> +++ b/drivers/mmc/core/host.c
>> @@ -330,6 +330,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
>>        spin_lock_init(&host->lock);
>>        init_waitqueue_head(&host->wq);
>>        INIT_DELAYED_WORK(&host->detect, mmc_rescan);
>> +       INIT_DELAYED_WORK(&host->start_bkops, mmc_start_periodic_bkops);
>>  #ifdef CONFIG_PM
>>        host->pm_notify.notifier_call = mmc_pm_notify;
>>  #endif
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index 2f0e11c..275555a 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -463,6 +463,24 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
>>        }
>>
>>        if (card->ext_csd.rev >= 5) {
>> +               /* check whether the eMMC card support BKOPS */
>> +               if (ext_csd[EXT_CSD_BKOPS_SUPPORT] & 0x1) {
>> +                       card->ext_csd.bkops = 1;
>> +                       card->ext_csd.bkops_en = ext_csd[EXT_CSD_BKOPS_EN];
>> +                       card->ext_csd.raw_bkops_status =
>> +                               ext_csd[EXT_CSD_BKOPS_STATUS];
>> +                       if (!card->ext_csd.bkops_en &&
>> +                               card->host->caps2 & MMC_CAP2_INIT_BKOPS) {
>> +                               err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>> +                                       EXT_CSD_BKOPS_EN, 1, 0);
> 
> I am not too comfortable tying a OTP register setting to a host
> controller capability.
> What if I had multiple instances of MMC and reuse the same HC, and
> each needs a different
> setting ? Or the same HC used in multiple SoCs ?
> A sysfs entry would be better - program the INIT when a user
> explicitly sets "enable_bkops" for the device
> that is being used.

Actually, at first time i didn't consider whether bkops is enabled or not.
Some card can be disabled for bkops enable bit.
If INIT_BKOPS is set, user didn't consider whether bkops is enabled or not.
because that's set to enable.
Right, this is used sysfs..but I think it's problem what is prefrence..

> 
>> +                               if (err)
>> +                                       pr_warning("%s: Enabling BKOPS failed\n",
>> +                                               mmc_hostname(card->host));
>> +                               else
>> +                                       card->ext_csd.bkops_en = 1;
>> +                       }
>> +               }
>> +
>>                /* check whether the eMMC card supports HPI */
>>                if (ext_csd[EXT_CSD_HPI_FEATURES] & 0x1) {
>>                        card->ext_csd.hpi = 1;
>> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
>> index 69370f4..bc8da17 100644
>> --- a/drivers/mmc/core/mmc_ops.c
>> +++ b/drivers/mmc/core/mmc_ops.c
>> @@ -399,6 +399,10 @@ int mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value,
>>        if (err)
>>                return err;
>>
>> +       /* No need to check card status in case of BKOPS switch*/
>> +       if (index == EXT_CSD_BKOPS_START)
>> +               return 0;
>> +
>>        /* Must check status to be sure of no errors */
>>        do {
>>                err = mmc_send_status(card, &status);
>> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
>> index d76513b..52b507d 100644
>> --- a/include/linux/mmc/card.h
>> +++ b/include/linux/mmc/card.h
>> @@ -76,6 +76,9 @@ struct mmc_ext_csd {
>>        bool                    hpi_en;                 /* HPI enablebit */
>>        bool                    hpi;                    /* HPI support bit */
>>        unsigned int            hpi_cmd;                /* cmd used as HPI */
>> +       bool                    bkops;          /* background support bit */
>> +       bool                    bkops_en;       /* background enable bit */
>> +       u8                      raw_exception_status;   /* 53 */
>>        unsigned int            data_sector_size;       /* 512 bytes or 4KB */
>>        unsigned int            data_tag_unit_size;     /* DATA TAG UNIT size */
>>        unsigned int            boot_ro_lock;           /* ro lock support */
>> @@ -93,6 +96,7 @@ struct mmc_ext_csd {
>>        u8                      raw_sec_erase_mult;     /* 230 */
>>        u8                      raw_sec_feature_support;/* 231 */
>>        u8                      raw_trim_mult;          /* 232 */
>> +       u8                      raw_bkops_status;       /* 246 */
>>        u8                      raw_sectors[4];         /* 212 - 4 bytes */
>>
>>        unsigned int            feature_support;
>> @@ -225,6 +229,9 @@ struct mmc_card {
>>  #define MMC_CARD_REMOVED       (1<<7)          /* card has been removed */
>>  #define MMC_STATE_HIGHSPEED_200        (1<<8)          /* card is in HS200 mode */
>>  #define MMC_STATE_SLEEP                (1<<9)          /* card is in sleep state */
>> +#define MMC_STATE_NEED_BKOPS   (1<<10)         /* card need to do BKOPS */
>> +#define MMC_STATE_DOING_BKOPS  (1<<11)         /* card is doing BKOPS */
>> +#define MMC_STATE_CHECK_BKOPS  (1<<12)         /* card need to check BKOPS */
>>        unsigned int            quirks;         /* card quirks */
>>  #define MMC_QUIRK_LENIENT_FN0  (1<<0)          /* allow SDIO FN0 writes outside of the VS CCCR range */
>>  #define MMC_QUIRK_BLKSZ_FOR_BYTE_MODE (1<<1)   /* use func->cur_blksize */
>> @@ -391,6 +398,9 @@ static inline void __maybe_unused remove_quirk(struct mmc_card *card, int data)
>>  #define mmc_card_ext_capacity(c) ((c)->state & MMC_CARD_SDXC)
>>  #define mmc_card_removed(c)    ((c) && ((c)->state & MMC_CARD_REMOVED))
>>  #define mmc_card_is_sleep(c)   ((c)->state & MMC_STATE_SLEEP)
>> +#define mmc_card_need_bkops(c) ((c)->state & MMC_STATE_NEED_BKOPS)
>> +#define mmc_card_doing_bkops(c)        ((c)->state & MMC_STATE_DOING_BKOPS)
>> +#define mmc_card_check_bkops(c) ((c)->state & MMC_STATE_CHECK_BKOPS)
>>
>>  #define mmc_card_set_present(c)        ((c)->state |= MMC_STATE_PRESENT)
>>  #define mmc_card_set_readonly(c) ((c)->state |= MMC_STATE_READONLY)
>> @@ -403,7 +413,13 @@ static inline void __maybe_unused remove_quirk(struct mmc_card *card, int data)
>>  #define mmc_card_set_ext_capacity(c) ((c)->state |= MMC_CARD_SDXC)
>>  #define mmc_card_set_removed(c) ((c)->state |= MMC_CARD_REMOVED)
>>  #define mmc_card_set_sleep(c)  ((c)->state |= MMC_STATE_SLEEP)
>> +#define mmc_card_set_need_bkops(c)     ((c)->state |= MMC_STATE_NEED_BKOPS)
>> +#define mmc_card_set_doing_bkops(c)    ((c)->state |= MMC_STATE_DOING_BKOPS)
>> +#define mmc_card_set_check_bkops(c) ((c)->state |= MMC_STATE_CHECK_BKOPS)
>>
>> +#define mmc_card_clr_need_bkops(c)     ((c)->state &= ~MMC_STATE_NEED_BKOPS)
>> +#define mmc_card_clr_doing_bkops(c)    ((c)->state &= ~MMC_STATE_DOING_BKOPS)
>> +#define mmc_card_clr_check_bkops(c) ((c)->state &= ~MMC_STATE_CHECK_BKOPS)
>>  #define mmc_card_clr_sleep(c)  ((c)->state &= ~MMC_STATE_SLEEP)
>>  /*
>>  * Quirk add/remove for MMC products.
>> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
>> index 1b431c7..c920250 100644
>> --- a/include/linux/mmc/core.h
>> +++ b/include/linux/mmc/core.h
>> @@ -134,6 +134,9 @@ struct mmc_host;
>>  struct mmc_card;
>>  struct mmc_async_req;
>>
>> +extern int mmc_stop_bkops(struct mmc_card *);
>> +extern int mmc_read_bkops_status(struct mmc_card *);
>> +extern int mmc_is_exception_event(struct mmc_card *, unsigned int);
>>  extern struct mmc_async_req *mmc_start_req(struct mmc_host *,
>>                                           struct mmc_async_req *, int *);
>>  extern int mmc_interrupt_hpi(struct mmc_card *);
>> @@ -163,6 +166,8 @@ extern int mmc_can_sanitize(struct mmc_card *card);
>>  extern int mmc_can_secure_erase_trim(struct mmc_card *card);
>>  extern int mmc_erase_group_aligned(struct mmc_card *card, unsigned int from,
>>                                   unsigned int nr);
>> +extern void mmc_start_periodic_bkops(struct work_struct *work);
>> +extern void mmc_start_bkops(struct mmc_card *card);
>>  extern unsigned int mmc_calc_max_discard(struct mmc_card *card);
>>
>>  extern int mmc_set_blocklen(struct mmc_card *card, unsigned int blocklen);
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index 0707d22..186d146 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> @@ -238,6 +238,8 @@ struct mmc_host {
>>  #define MMC_CAP2_BROKEN_VOLTAGE        (1 << 7)        /* Use the broken voltage */
>>  #define MMC_CAP2_DETECT_ON_ERR (1 << 8)        /* On I/O err check card removal */
>>  #define MMC_CAP2_HC_ERASE_SZ   (1 << 9)        /* High-capacity erase size */
>> +#define MMC_CAP2_INIT_BKOPS    (1 << 10)       /* To enable BKOPS */
>> +#define MMC_CAP2_BKOPS         (1 << 11)       /* BKOPS supported */
>>
>>        mmc_pm_flag_t           pm_caps;        /* supported pm features */
>>        unsigned int        power_notify_type;
>> @@ -320,6 +322,8 @@ struct mmc_host {
>>
>>        unsigned int            actual_clock;   /* Actual HC clock rate */
>>
>> +       struct delayed_work     start_bkops;    /* Periodic bkops start */
>> +
>>        unsigned long           private[0] ____cacheline_aligned;
>>  };
>>
>> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
>> index d425cab..06afeb4 100644
>> --- a/include/linux/mmc/mmc.h
>> +++ b/include/linux/mmc/mmc.h
>> @@ -139,6 +139,7 @@ static inline bool mmc_op_multi(u32 opcode)
>>  #define R1_CURRENT_STATE(x)    ((x & 0x00001E00) >> 9) /* sx, b (4 bits) */
>>  #define R1_READY_FOR_DATA      (1 << 8)        /* sx, a */
>>  #define R1_SWITCH_ERROR                (1 << 7)        /* sx, c */
>> +#define R1_EXCEPTION_EVENT     (1 << 6)        /* sx, a */
>>  #define R1_APP_CMD             (1 << 5)        /* sr, c */
>>
>>  #define R1_STATE_IDLE  0
>> @@ -274,12 +275,15 @@ struct _mmc_csd {
>>  #define EXT_CSD_FLUSH_CACHE            32      /* W */
>>  #define EXT_CSD_CACHE_CTRL             33      /* R/W */
>>  #define EXT_CSD_POWER_OFF_NOTIFICATION 34      /* R/W */
>> +#define EXT_CSD_EXCEPTION_STATUS       54      /* RO */
>>  #define EXT_CSD_DATA_SECTOR_SIZE       61      /* R */
>>  #define EXT_CSD_GP_SIZE_MULT           143     /* R/W */
>>  #define EXT_CSD_PARTITION_ATTRIBUTE    156     /* R/W */
>>  #define EXT_CSD_PARTITION_SUPPORT      160     /* RO */
>>  #define EXT_CSD_HPI_MGMT               161     /* R/W */
>>  #define EXT_CSD_RST_N_FUNCTION         162     /* R/W */
>> +#define EXT_CSD_BKOPS_EN               163     /* R/W */
>> +#define EXT_CSD_BKOPS_START            164     /* W */
>>  #define EXT_CSD_SANITIZE_START         165     /* W */
>>  #define EXT_CSD_WR_REL_PARAM           166     /* RO */
>>  #define EXT_CSD_BOOT_WP                        173     /* R/W */
>> @@ -313,11 +317,13 @@ struct _mmc_csd {
>>  #define EXT_CSD_PWR_CL_200_360         237     /* RO */
>>  #define EXT_CSD_PWR_CL_DDR_52_195      238     /* RO */
>>  #define EXT_CSD_PWR_CL_DDR_52_360      239     /* RO */
>> +#define EXT_CSD_BKOPS_STATUS           246     /* RO */
>>  #define EXT_CSD_POWER_OFF_LONG_TIME    247     /* RO */
>>  #define EXT_CSD_GENERIC_CMD6_TIME      248     /* RO */
>>  #define EXT_CSD_CACHE_SIZE             249     /* RO, 4 bytes */
>>  #define EXT_CSD_TAG_UNIT_SIZE          498     /* RO */
>>  #define EXT_CSD_DATA_TAG_SUPPORT       499     /* RO */
>> +#define EXT_CSD_BKOPS_SUPPORT          502     /* RO */
>>  #define EXT_CSD_HPI_FEATURES           503     /* RO */
>>
>>  /*
>> @@ -386,4 +392,18 @@ struct _mmc_csd {
>>  #define MMC_SWITCH_MODE_CLEAR_BITS     0x02    /* Clear bits which are 1 in value */
>>  #define MMC_SWITCH_MODE_WRITE_BYTE     0x03    /* Set target to value */
>>
>> +/*
>> + * BKOPS status level
>> + */
>> +#define EXT_CSD_BKOPS_LEVEL_2          0x2
>> +#define EXT_CSD_BKOPS_LEVEL_3          0x3
>> +
>> +/*
>> + * EXCEPTION_EVENT_STATUS field (eMMC4.5)
>> + */
>> +#define EXT_CSD_URGENT_BKOPS           BIT(0)
>> +#define EXT_CSD_DYNCAP_NEEDED          BIT(1)
>> +#define EXT_CSD_SYSPOOL_EXHAUSTED      BIT(2)
>> +#define EXT_CSD_PACKED_FAILURE         BIT(3)
>> +
>>  #endif /* LINUX_MMC_MMC_H */
> 
> 
> Overall, my significant concern is about performance.
> IIUC, There is a ext_csd query during the execution of _every_ request
> - this is far too obsessive and could kill throughput.

I didn't find the performance issue. didn't _every_ request..only check to set bkops_need_check.

> A more pragmatic approach would be to trigger on a threshold of number
> of writes or discards (ex: After 1M sector writes)

I will try to this approach.

> This means that a predominantly read only disk, which wouldn't need
> any BKOPS, wouldn't have any overhead.
> 
> Let me know if my assumption is incorrect.

Thanks for reviwe.

Best Regards,
Jaehoon Chung

> 
> ~Venkat.
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