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

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

Hi Venkat,
>>> +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.

Could you explain more detail? In my case, it's working at every 5sec.

> 
>>
>>> +{
>>> +       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.

We need to read bkops-status register. so card is set to check-bkops.

>>
>>> +
>>> +       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

 When URGENT_BKOPS is triggered, we didn't know which level.
It's just guessing Level-3 or Level-2.
In my case, status should be level-1 or level-0.

> 
>>
>>> +               } 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 ?

If required the request, then it should be stopped.

> 
> 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)

In this case, we need to use bkops feature, I think that just using discard.
How think about? if you have other opinion, let me know, plz.
Then i will apply to next-patch.

Best Regards,
Jaehoon Chung

> 
> 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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