On Wed, Dec 11, 2013 at 11:01 AM, Shawn Guo [off-list ref] wrote:

On Tue, Dec 10, 2013 at 08:56:07PM +0800, Dong Aisheng wrote:

quoted

For host controllers using SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK, since the card
clock is changed dynamically for different cards, it does not make sense
to use the maximum host clock to calculate max_discard_to which may lead
the max_discard_to to be much smaller than its capbility and affect the card
discard performance a lot.
e.g. the host clock is 200Mhz, but the card is working on 50Mhz. Then the
max_discard_to is only 1/4 of its real capbility.

In this patch, it uses the actual_clock to calculate the max_discard_to
dynamically as long as a new clock speed is set.

Tested with a high speed SDHC card shows:
Originally:
mmc1: new high speed SDHC card at address aaaa
mmc1: calculated max. discard sectors 49152 for timeout 1355 ms
Now:
mmc1: new high speed SDHC card at address aaaa
mmc1: calculated max. discard sectors 712704 for timeout 5422 ms
The max_discard_sectors will increase a lot which will also improve discard
performance a lot.

The one known limitation of this approach is that it does not cover the special
case for user changes the clock via sysfs, since the max_discard_to is only
initialised for one time during the mmc queue init.

Signed-off-by: Dong Aisheng <redacted>
---
 drivers/mmc/host/sdhci.c |   27 +++++++++++++++++++++------
 1 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 4cc3bd6..9be8a79 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c

@@ -1143,14 +1143,14 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
      unsigned long timeout;

      if (clock && clock == host->clock)
-             return;
+             goto out;

I do not quite understand this change.  Why do we need to recalculate
max_discard_to if the clock does not change since the last time that
the function is called?

Good catch.
It's safe to return directly here.
Will update in v2.

Regards
Dong Aisheng

Shawn

quoted

      host->mmc->actual_clock = 0;

      if (host->ops->set_clock) {
              host->ops->set_clock(host, clock);
              if (host->quirks & SDHCI_QUIRK_NONSTANDARD_CLOCK)
-                     return;
+                     goto out;
      }

      sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);

@@ -1249,6 +1249,19 @@ clock_set:

 out:
      host->clock = clock;
+
+     /* update timeout_clk and max_discard_to once the SDCLK is changed */
+     if (host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK && clock) {
+             host->timeout_clk = host->mmc->actual_clock ?
+                                     host->mmc->actual_clock / 1000 :
+                                     host->clock / 1000;
+             if (host->ops->get_max_timeout)
+                     host->mmc->max_discard_to =
+                                     host->ops->get_max_timeout(host);
+             else
+                     host->mmc->max_discard_to = (1 << 27) /
+                                     host->timeout_clk;
+     }
 }

 static inline void sdhci_update_clock(struct sdhci_host *host)

@@ -2939,10 +2952,12 @@ int sdhci_add_host(struct sdhci_host *host)
      if (host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)
              host->timeout_clk = mmc->f_max / 1000;

-     if (host->ops->get_max_timeout)
-             mmc->max_discard_to = host->ops->get_max_timeout(host);
-     else
-             mmc->max_discard_to = (1 << 27) / host->timeout_clk;
+     if (!(host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)) {
+             if (host->ops->get_max_timeout)
+                     mmc->max_discard_to = host->ops->get_max_timeout(host);
+             else
+                     mmc->max_discard_to = (1 << 27) / host->timeout_clk;
+     }

      mmc->caps |= MMC_CAP_SDIO_IRQ | MMC_CAP_ERASE | MMC_CAP_CMD23;

--

1.7.2.rc3

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