Re: [PATCH v11] mmc: support BKOPS feature for eMMC

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

On 07/29/2012 11:33 AM, Minchan Kim wrote:
> On Tue, Jul 24, 2012 at 10:56 AM, 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. Immediately run BKOPS if required.
>> read/write operations should be requested during BKOPS(LEVEL-1),
>> then issue HPI to interrupt the ongoing BKOPS
>> and service the foreground operation.
>> (This patch is only control the LEVEL2/3.)
>>
>> When repeating the writing 1GB data, at a certain time, performance is decreased.
>> At that time, card is also triggered the Level-3 or Level-2.
>> After running bkops, performance is recovered.
>>
>> Future considerations
>>  * Check BKOPS_LEVEL=1 and start BKOPS in a preventive manner.
>>  * Interrupt ongoing BKOPS before powering off the card.
>>  * How get BKOPS_STATUS value.(periodically send ext_csd command?)
>>  * If use periodic bkops, also consider runtime_pm control.
>>
>> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>> Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
>> Signed-off-by: Maya Erez <merez@codeaurora.org>
>> ---
>> Changelog v11:
>>         - removed the MMC_CAP2_BKOPS.
>>                 : if card support and enable bkops, then use it.
>> Changelog v10:
>>         - Based on latest mmc-next
>>         - Only control the level-2/3.
>>                 : If triggered upper than level2, immediately start bkops.
>>         - Remove the BKOPS_CAP2_INIT_BKOPS (move into mmc-util)
>>         - change use_busy_signal instead of waiting_for_prog_done for __mmc_switch
>>         - Remove the useless code.
>>         - Add the from_exception to prepare the periodic bkops.
>> Changelog V9:
>>         - Rebased on patch-v7.
>>         - Added Konstantin and Maya's patch
>>                 : mmc:core: Define synchronous BKOPS timeout
>>                 : mmc:core: eMMC4.5 BKOPS fixes
>>         - Removed periodic bkops
>>                 : This feature will do in future work
>>         - Add __mmc_switch() for waiting_for_prod_done.
>>
>> 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/core/core.c    |  145 +++++++++++++++++++++++++++++++++++++++++++-
>>  drivers/mmc/core/mmc.c     |   11 +++
>>  drivers/mmc/core/mmc_ops.c |   26 +++++++-
>>  include/linux/mmc/card.h   |    8 +++
>>  include/linux/mmc/core.h   |    4 +
>>  include/linux/mmc/mmc.h    |   19 ++++++
>>  6 files changed, 207 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 8ac5246..ed2cc93 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -41,6 +41,12 @@
>>  #include "sd_ops.h"
>>  #include "sdio_ops.h"
>>
>> +/*
>> + * The Background operation can take a long time, depends on the house keeping
>> + * operations the card has to peform
>> + */
>> +#define MMC_BKOPS_MAX_TIMEOUT  (4 * 60 * 1000) /* max time to wait in ms */
>> +
>>  static struct workqueue_struct *workqueue;
>>  static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
>>
>> @@ -245,6 +251,70 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
>>         host->ops->request(host, mrq);
>>  }
>>
>> +/**
>> + *     mmc_start_bkops - start BKOPS for supported cards
>> + *     @card: MMC card to start BKOPS
>> + *     @form_exception: A flags to indicate if this function was
>> + *                     called due to an exception raised by the card
>> + *
>> + *     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, bool from_exception)
>> +{
>> +       int err;
>> +       int timeout;
>> +       bool use_busy_signal;
>> +
>> +       BUG_ON(!card);
>> +
>> +       if (!card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
>> +               return;
>> +
>> +       err = mmc_read_bkops_status(card);
>> +       if (err) {
>> +               pr_err("%s: Didn't read bkops status : %d\n",
>> +                      mmc_hostname(card->host), err);
>> +               return;
>> +       }
>> +
>> +       if (!card->ext_csd.raw_bkops_status)
>> +               return;
>> +
>> +       if (card->ext_csd.raw_bkops_status < EXT_CSD_BKOPS_LEVEL_2
>> +           && (from_exception))
>> +               return;
>> +
>> +       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;
>> +       } else {
>> +               timeout = 0;
>> +               use_busy_signal = false;
>> +       }
>> +
>> +       err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>> +                       EXT_CSD_BKOPS_START, 1, timeout, use_busy_signal);
>> +       if (err) {
>> +               pr_warn("%s: error %d starting bkops\n",
>> +                          mmc_hostname(card->host), err);
>> +               goto out;
>> +       }
>> +
>> +       /*
>> +        * For urgent bkops status (LEVEL_2 and more)
>> +        * bkops executed synchronously, otherwise
>> +        * the operation is in progress
>> +        */
>> +       if (!use_busy_signal)
>> +               mmc_card_set_doing_bkops(card);
>> +out:
>> +       mmc_release_host(card->host);
>> +}
>> +EXPORT_SYMBOL(mmc_start_bkops);
>> +
>>  static void mmc_wait_done(struct mmc_request *mrq)
>>  {
>>         complete(&mrq->completion);
>> @@ -354,6 +424,14 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
>>         if (host->areq) {
>>                 mmc_wait_for_req_done(host, host->areq->mrq);
>>                 err = host->areq->err_check(host->card, host->areq);
>> +               /*
>> +                * Check BKOPS urgency for each R1 response
>> +                */
>> +               if (host->card && mmc_card_mmc(host->card) &&
>> +               ((mmc_resp_type(host->areq->mrq->cmd) == MMC_RSP_R1) ||
>> +                (mmc_resp_type(host->areq->mrq->cmd) == MMC_RSP_R1B)) &&
>> +               (host->areq->mrq->cmd->resp[0] & R1_EXCEPTION_EVENT))
>> +                       mmc_start_bkops(host->card, true);
>>         }
>>
>>         if (!err && areq)
>> @@ -489,6 +567,53 @@ 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 stop 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;
>> +
>> +       BUG_ON(!card);
>> +       err = mmc_interrupt_hpi(card);
>> +
>> +       /*
>> +        * if err is EINVAL, it's status that can't issue HPI.
>> +        * it should complete the BKOPS.
>> +        */
>> +       if (!err || (err == -EINVAL)) {
>> +               mmc_card_clr_doing_bkops(card);
>> +               err = 0;
>> +       }
>> +
>> +       return err;
>> +}
>> +EXPORT_SYMBOL(mmc_stop_bkops);
>> +
>> +int mmc_read_bkops_status(struct mmc_card *card)
>> +{
>> +       int err;
>> +       u8 ext_csd[512];
> 
> 512 byte stack? Isn't it really a problem?
How about this?

+int mmc_read_bkops_status(struct mmc_card *card)
+{
+	int err;
+	u8 *ext_csd;
+
+	ext_csd = kmalloc(512, GFP_KERNEL);
+	if (!ext_csd) {
+		pr_err("%s: could not allocate a buffer to "
+			"receive the ext_csd.\n", mmc_hostname(card->host));
+		return -ENOMEM;
+	}
+
+	mmc_claim_host(card->host);
+	err = mmc_send_ext_csd(card, ext_csd);
+	mmc_release_host(card->host);
+	if (err)
+		goto out;
+
+	card->ext_csd.raw_bkops_status = ext_csd[EXT_CSD_BKOPS_STATUS];
+	card->ext_csd.raw_exception_status = ext_csd[EXT_CSD_EXP_EVENTS_STATUS];
+out:
+	kfree(ext_csd);
+	return err;
+}
+EXPORT_SYMBOL(mmc_read_bkops_status);

Best Regards,
Jaehoon Chung