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    Subject[PATCH v2 12/16] mmc: sysfs: Add sysfs entry for tuning preempt_time_threshold
    Date
    When High Priority Interrupt (HPI) is enabled, ongoing requests
    might be preempted. It is worthwhile to not preempt some requests
    which have progressed in the underlying driver for some time.

    The threshold of elapsed time after which HPI is not useful can
    be tuned on a per-device basis, using the hpi_time_threshold
    sysfs entry.

    Signed-off-by: Venkatraman S <svenkatr@ti.com>
    ---
    drivers/mmc/core/mmc.c | 25 +++++++++++++++++++++++++
    include/linux/mmc/card.h | 1 +
    2 files changed, 26 insertions(+)

    diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
    index 54df5ad..b7dbea1 100644
    --- a/drivers/mmc/core/mmc.c
    +++ b/drivers/mmc/core/mmc.c
    @@ -624,6 +624,30 @@ MMC_DEV_ATTR(enhanced_area_offset, "%llu\n",
    card->ext_csd.enhanced_area_offset);
    MMC_DEV_ATTR(enhanced_area_size, "%u\n", card->ext_csd.enhanced_area_size);

    +static ssize_t mmc_hpi_threhold_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct mmc_card *card = mmc_dev_to_card(dev);
    + return sprintf(buf, "%d\n", card->preempt_time_threshold);
    +}
    +
    +static ssize_t mmc_hpi_threshold_store(struct device *dev,
    + struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + unsigned long threshold;
    + struct mmc_card *card = mmc_dev_to_card(dev);
    +
    + if (kstrtoul(buf, 0, &threshold))
    + return -EINVAL;
    + if (threshold)
    + card->preempt_time_threshold = threshold;
    + return count;
    +}
    +
    +DEVICE_ATTR(hpi_time_threshold, S_IRWXU, mmc_hpi_threhold_show,
    + mmc_hpi_threshold_store);
    +
    static struct attribute *mmc_std_attrs[] = {
    &dev_attr_cid.attr,
    &dev_attr_csd.attr,
    @@ -638,6 +662,7 @@ static struct attribute *mmc_std_attrs[] = {
    &dev_attr_serial.attr,
    &dev_attr_enhanced_area_offset.attr,
    &dev_attr_enhanced_area_size.attr,
    + &dev_attr_hpi_time_threshold.attr,
    NULL,
    };

    diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
    index 629b823..2a0da29 100644
    --- a/include/linux/mmc/card.h
    +++ b/include/linux/mmc/card.h
    @@ -245,6 +245,7 @@ struct mmc_card {
    unsigned int erase_shift; /* if erase unit is power 2 */
    unsigned int pref_erase; /* in sectors */
    u8 erased_byte; /* value of erased bytes */
    + unsigned int preempt_time_threshold; /* ms for checking hpi usage */

    u32 raw_cid[4]; /* raw card CID */
    u32 raw_csd[4]; /* raw card CSD */
    --
    1.7.10.rc2


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