On Jan 5, 2011, at 1:39 AM, zhangfei gao wrote:
> From 7554ead744bfdc7304a7ae9fb227212bf548161a Mon Sep 17 00:00:00 2001
> From: Zhangfei Gao <zhangfei.gao@xxxxxxxxxxx>
> Date: Wed, 5 Jan 2011 17:21:00 -0500
> Subject: [PATCH] mmc: sdhci stop SDCLK during asynchronous interrupt peroid
>
> V3 controller could stop SDCLK during asynchronous interrupt peroid
> to save power, via set SDHCI_CTRL2_AINT bit 14 of
> SDHCI_HOST_CONTROL2(0x3e)
> Two conditions:
> 1. card support asynchronous interrupt
> 2. Asynchronous interrupt support is set to 1 in the capabilities register.
>
> How to enable: mmc->caps |= MMC_CAP_CLOCK_GATE
>
> Signed-off-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci.c | 14 ++++++++++++++
> drivers/mmc/host/sdhci.h | 2 ++
> include/linux/mmc/host.h | 2 ++
> 3 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index aafbb42..946b947 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1261,6 +1261,15 @@ static void sdhci_set_ios(struct mmc_host *mmc,
> struct mmc_ios *ios)
> if(host->quirks & SDHCI_QUIRK_RESET_CMD_DATA_ON_IOS)
> sdhci_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);
>
> + if (mmc->caps & MMC_CAP_CLOCK_GATE) {
> + u16 con;
> +
> + con = readw(host->ioaddr + SDHCI_HOST_CONTROL2);
> + con |= SDHCI_CTRL2_AINT;
> + writew(con, host->ioaddr + SDHCI_HOST_CONTROL2);
> + }
> +
> +
This will enable clock gating for SD/eMMC and SDIO cards. This is not a good idea for SDIO where
there are known issues. This is one reason the software clock gating code does not enable
clock gating on SDIO. Not all SDIO cards can work.
It does not handle the case clock gating being supported in pre SD 3.0 controllers.
See my patch on h/w clock gating -- if there are issues with the patch would appreciate comments.
> out:
> mmiowb();
> spin_unlock_irqrestore(&host->lock, flags);
> @@ -1808,6 +1817,11 @@ int sdhci_add_host(struct sdhci_host *host)
> mmc->caps |= (MMC_CAP_1_8V_DDR);
> }
>
> + if (mmc->caps & MMC_CAP_CLOCK_GATE) {
> + if (!(caps & SDHCI_CAN_ASYN_INT))
> + mmc->caps &= ~MMC_CAP_CLOCK_GATE;
> + }
> +
> if (host->quirks & SDHCI_QUIRK_FORCE_DMA)
> host->flags |= SDHCI_USE_SDMA;
> else if (!(caps & SDHCI_CAN_DO_SDMA))
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index c4bd5dd..907de87 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -153,6 +153,7 @@
> #define SDHCI_CTRL2_SDR104 0x0003
> #define SDHCI_CTRL2_DDR50 0x0004
> #define SDHCI_CTRL2_1_8V 0x0008
> +#define SDHCI_CTRL2_AINT 0x4000
>
> #define SDHCI_CAPABILITIES 0x40
> #define SDHCI_TIMEOUT_CLK_MASK 0x0000003F
> @@ -172,6 +173,7 @@
> #define SDHCI_CAN_VDD_300 0x02000000
> #define SDHCI_CAN_VDD_180 0x04000000
> #define SDHCI_CAN_64BIT 0x10000000
> +#define SDHCI_CAN_ASYN_INT 0x20000000
>
> #define SDHCI_CAPABILITIES_1 0x44
> #define SDHCI_CAN_SDR50 0x00000001
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index bcb793e..2a53a94 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -173,6 +173,8 @@ struct mmc_host {
> /* DDR mode at 1.2V */
> #define MMC_CAP_POWER_OFF_CARD (1 << 13) /* Can power off after boot */
> #define MMC_CAP_BUS_WIDTH_TEST (1 << 14) /* CMD14/CMD19 bus width ok */
> +#define MMC_CAP_CLOCK_GATE (1 << 15) /* V3 controller */
> + /* support clock gating */
>
> mmc_pm_flag_t pm_caps; /* supported pm features */
>
> --
> 1.7.0.4
> --
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