Re: mmc: sdhci stop SDCLK during asynchronous interrupt peroid

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On Jan 6, 2011, at 2:44 AM, zhangfei gao wrote:

> On Wed, Jan 5, 2011 at 11:30 AM, Philip Rakity <prakity@xxxxxxxxxxx> wrote:
>> 
>> 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 is enabled only by setting caps MMC_CAP_CLOCK_GATE, for example the
> code to verify emmc/sd in sdhci-pxa.c
> 
>        if (pdata && pdata->flags & PXA_FLAG_CONTROL_CLK_GATE) {
>                /* v3 controller could support clock gating */
>                host->mmc->caps |= MMC_CAP_CLOCK_GATE;
>        }
> SDIO is not enabled since no PXA_FLAG_CONTROL_CLK_GATE in flags.
> In the experiment, we find sdio (wifi) power does not change a lot
> with or without clock gate, it mainly rely on wifi itself, for example
> wifi goto deep sleep mode.
> 

how do you know what card will be plugged in ?  this only works work hard wired cards not for cards plugged into a slot.

>> 
>> It does not handle the case clock gating being supported in pre SD 3.0 controllers.
> It is true, soft clock gating also be verified in SD 2.0 controller,
> such as pxa955.
> 
>> 
>> 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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>> 
>> 

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