> -----Original Message-----
> From:
linux-mmc-owner@vger.kernel.org
> [mailto:linux-mmc-owner@vger.kernel.org] On Behalf Of Pierre Tardy
> Sent: Wednesday, December 22, 2010 9:14 PM
> To: linux-mmc@vger.kernel.org;
linux-kernel@vger.kernel.org
> Cc: Pierre Tardy; Chris Ball; Andrew Morton; Alan Cox; Takashi Iwai; Maxim
> Levitsky; Linus Walleij; Ohad Ben-Cohen; Gao, Yunpeng
> Subject: [RFC] sdhci: use ios->clock to know when sdhci is idle
>
> This allows sdhci to detect its own activity and to autosuspend
> when not used
>
> inspired from mmci: handle clock frequency 0 properly
> From Linus Walleij <linus.walleij@stericsson.com>
> author of mmc aggressive clock gating fw.
>
> The idea of using mmc clock gating fw in order to power gate the
> sdhci is simple (hope no too simplistic):
> Whenever the mmc fw tells we dont need the MMC clock, we dont need
> the sdhci power as well.
>
> This does not mean that the child (card) is
> suspended. In case of a Wifi SDIO card, the card will be suspended
> and resumed according to the ifconfig up/down status.
> Even if the Wifi interface is up, user might not use the network.
> Sdhci can be powered off during those period. It is up to the HW
> implementation to implement smart enough power gating to still
> support enough always-on circuitry allowing to detect sdio
> interrupts.
>
> This patch goes on top of Yunpeng's patch available on patchwork:
> 378052 [v2,2/3] mmc: enable runtime PM support of sdhci host controller
>
> CC: Chris Ball <cjb@laptop.org>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Alan Cox <alan@linux.intel.com>
> CC: Takashi Iwai <tiwai@suse.de>
> CC: Maxim Levitsky <maximlevitsky@gmail.com>
> CC: Linus Walleij <linus.walleij@stericsson.com>
> CC: Ohad Ben-Cohen <ohad@wizery.com>
> CC: Yunpeng Gao <yunpeng.gao@intel.com>
>
> Signed-off-by: Pierre Tardy <tardyp@gmail.com>
> ---
> drivers/mmc/host/sdhci.c | 20 ++++++++++++++++++++
> include/linux/mmc/sdhci.h | 1 +
> 2 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index a298fb0..a648330 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1161,6 +1161,7 @@ static void sdhci_set_ios(struct mmc_host *mmc,
> struct mmc_ios *ios)
> {
> struct sdhci_host *host;
> unsigned long flags;
> + unsigned int lastclock;
> u8 ctrl;
>
> host = mmc_priv(mmc);
> @@ -1171,6 +1172,24 @@ static void sdhci_set_ios(struct mmc_host *mmc,
> struct mmc_ios *ios)
> goto out;
>
> /*
> + * get/put runtime_pm usage counter at ios->clock transitions
> + * We need to do it before any other chip access, as sdhci could
> + * be power gated
> + */
> + lastclock = host->iosclock;
> + host->iosclock = ios->clock;
> + if (lastclock == 0 && ios->clock != 0) {
> + spin_unlock_irqrestore(&host->lock, flags);
> + pm_runtime_get_sync(&host->parent.dev);
> + spin_lock_irqsave(&host->lock, flags);
> + } else if (lastclock != 0 && ios->clock == 0) {
> + spin_unlock_irqrestore(&host->lock, flags);
> + pm_runtime_put_autosuspend(&host->parent.dev);
> + spin_lock_irqsave(&host->lock, flags);
> + /* no need to configure the rest.. */
> + goto out;
> + }
> + /*
> * Reset the chip on each power off.
> * Should clear out any weird states.
> */
> @@ -1779,6 +1798,7 @@ struct sdhci_host *sdhci_alloc_host(struct device
> *dev,
>
> host = mmc_priv(mmc);
> host->mmc = mmc;
> + host->iosclock = 0;
>
> return host;
> }
> diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
> index 0d953f5..78c1528 100644
> --- a/include/linux/mmc/sdhci.h
> +++ b/include/linux/mmc/sdhci.h
> @@ -114,6 +114,7 @@ struct sdhci_host {
> unsigned int timeout_clk; /* Timeout freq (KHz) */
>
> unsigned int clock; /* Current clock (MHz) */
> + unsigned int iosclock; /* Last clock asked via set_ios */
> u8 pwr; /* Current voltage */
>
> struct mmc_request *mrq; /* Current request */
> --
> 1.7.1
>
> --
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