On Tue, Dec 10, 2013 at 08:56:07PM +0800, Dong Aisheng wrote:
> 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 <b29396@xxxxxxxxxxxxx>
> ---
> 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?
Shawn
>
> 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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