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    Subject[PATCH 1/3] mmc: core: Avoid hogging the CPU while polling for busy in the I/O err path
    Date
    When mmc_blk_fix_state() sends a CMD12 to try to move the card into the
    transfer state, it calls card_busy_detect() to poll for the card's state
    with CMD13. This is done without any delays in between the commands being
    sent.

    Rather than fixing card_busy_detect() in this regards, let's instead
    convert into using the common mmc_poll_for_busy(), which also helps us to
    avoid open-coding.

    Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
    ---
    drivers/mmc/core/block.c | 2 +-
    drivers/mmc/core/mmc_ops.c | 4 +++-
    drivers/mmc/core/mmc_ops.h | 1 +
    3 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
    index 88f4c215caa6..1b5576048cdb 100644
    --- a/drivers/mmc/core/block.c
    +++ b/drivers/mmc/core/block.c
    @@ -1630,7 +1630,7 @@ static int mmc_blk_fix_state(struct mmc_card *card, struct request *req)

    mmc_blk_send_stop(card, timeout);

    - err = card_busy_detect(card, timeout, NULL);
    + err = mmc_poll_for_busy(card, timeout, false, MMC_BUSY_IO);

    mmc_retune_release(card->host);

    diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
    index 973756ed4016..e2c431c0ce5d 100644
    --- a/drivers/mmc/core/mmc_ops.c
    +++ b/drivers/mmc/core/mmc_ops.c
    @@ -435,7 +435,7 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
    u32 status = 0;
    int err;

    - if (host->ops->card_busy) {
    + if (data->busy_cmd != MMC_BUSY_IO && host->ops->card_busy) {
    *busy = host->ops->card_busy(host);
    return 0;
    }
    @@ -457,6 +457,7 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
    break;
    case MMC_BUSY_HPI:
    case MMC_BUSY_EXTR_SINGLE:
    + case MMC_BUSY_IO:
    break;
    default:
    err = -EINVAL;
    @@ -521,6 +522,7 @@ int mmc_poll_for_busy(struct mmc_card *card, unsigned int timeout_ms,

    return __mmc_poll_for_busy(card, timeout_ms, &mmc_busy_cb, &cb_data);
    }
    +EXPORT_SYMBOL_GPL(mmc_poll_for_busy);

    bool mmc_prepare_busy_cmd(struct mmc_host *host, struct mmc_command *cmd,
    unsigned int timeout_ms)
    diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
    index 41ab4f573a31..ae25ffc2e870 100644
    --- a/drivers/mmc/core/mmc_ops.h
    +++ b/drivers/mmc/core/mmc_ops.h
    @@ -15,6 +15,7 @@ enum mmc_busy_cmd {
    MMC_BUSY_ERASE,
    MMC_BUSY_HPI,
    MMC_BUSY_EXTR_SINGLE,
    + MMC_BUSY_IO,
    };

    struct mmc_host;
    --
    2.25.1
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