Re: [PATCH]mmc: sdhci: use udelay instead of mdelay for some cases

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2011/10/27 Shawn.Dong <shawn.dong.cx@xxxxxxxxx>:
> sdhci_set_clock or sdhci_reset or sdhci_send_command may be used in
> critical region which is protected by spin_lock_irqsave. Thus, these
> functions will delay the responsing of the kernel interrupts.
>
> So in this case, using a mdelay will cause unnecessary latency. Our
> hardware, in most case will not cause 1ms to finish its job. Using
> udelay instead can reduce it.
>
> By default, sdhci_do_set_ios will need about 1ms to finish in my platform.
> After using udelay instead, sdhci_do_set_ios only need a few microseconds.
>
> Signed-off-by: Shawn.Dong <Shawn.dong.cx@xxxxxxxxx>

ACK, see my patch as well:
http://www.spinics.net/lists/linux-mmc/msg10257.html

> ---
>  drivers/mmc/host/sdhci.c |   12 ++++++------
>  1 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 6d8eea3..9314cd1 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -195,7 +195,7 @@ static void sdhci_reset(struct sdhci_host *host, u8 mask)
>                host->clock = 0;
>
>        /* Wait max 100 ms */
> -       timeout = 100;
> +       timeout = 10000;
>
>        /* hw clears the bit when it's done */
>        while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
> @@ -206,7 +206,7 @@ static void sdhci_reset(struct sdhci_host *host, u8 mask)
>                        return;
>                }
>                timeout--;
> -               mdelay(1);
> +               udelay(10);
>        }
>
>        if (host->ops->platform_reset_exit)
> @@ -959,7 +959,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>        WARN_ON(host->cmd);
>
>        /* Wait max 10 ms */
> -       timeout = 10;
> +       timeout = 1000;
>
>        mask = SDHCI_CMD_INHIBIT;
>        if ((cmd->data != NULL) || (cmd->flags & MMC_RSP_BUSY))
> @@ -980,7 +980,7 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>                        return;
>                }
>                timeout--;
> -               mdelay(1);
> +               udelay(10);
>        }
>
>        mod_timer(&host->timer, jiffies + 10 * HZ);
> @@ -1140,7 +1140,7 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>        sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
>
>        /* Wait max 20 ms */
> -       timeout = 20;
> +       timeout = 2000;
>        while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
>                & SDHCI_CLOCK_INT_STABLE)) {
>                if (timeout == 0) {
> @@ -1150,7 +1150,7 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>                        return;
>                }
>                timeout--;
> -               mdelay(1);
> +               udelay(10);
>        }
>
>        clk |= SDHCI_CLOCK_CARD_EN;
> --
> 1.7.3.4

-barry
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