linux-kernel - Re: [PATCH 2/3] mmc: dw_mmc: simplify the SDMMC_CLKEN_LOW

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Date:	Mon, 17 Aug 2015 07:52:00 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	linux-sunxi <linux-sunxi@...glegroups.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	David Lanzendörfer <david.lanzendoerfer@....ch>,
	Hans de Goede <hdegoede@...hat.com>,
	Chen-Yu Tsai <wens@...e.org>, Arnd Bergmann <arnd@...db.de>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/3] mmc: dw_mmc: simplify the SDMMC_CLKEN_LOW_PWR logic

Hello,

On 17 August 2015 at 03:55, Jaehoon Chung <jh80.chung@...sung.com> wrote:
> Hi, Michal.
>
> On 08/12/2015 09:23 PM, Michal Suchanek wrote:
>> The driver has open-coded test for SDIO cards. Use the mmc core provided
>> MMC_QUIRK_BROKEN_CLK_GATING flag instead.
>
> Did you use the clock-gating for SDIO cards?
> Doesn't MMC_CAP_SDIO_IRQ bit set? Which case is broken?
> Could you explain to me more?

The core flag for disabling power saving is MMC_QUIRK_BROKEN_CLK_GATING.

It may coincide with MMC_CAP_SDIO_IRQ but that's different flag for
different purpose.

MMC_QUIRK_BROKEN_CLK_GATING is currently set for all SDIO cards except
for cards on a whitelist.

I don't know any particular SDIO card that has problems when the clock
is off and does not use an IRQ.

Thanks

Michal

>
> Best Regards,
> Jaehoon Chung
>
>>
>> As a bonus this may enable clock gating on SDIO cards that are known to
>> work with it.
>>
>> Signed-off-by: Michal Suchanek <hramrach@...il.com>
>> ---
>>  drivers/mmc/host/dw_mmc.c | 33 +++++++++++++++------------------
>>  1 file changed, 15 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 40e9d8e..3bc9fd7 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -1335,27 +1335,24 @@ static void dw_mci_init_card(struct mmc_host *mmc, struct mmc_card *card)
>>        * description of the CLKENA register we should disable low power mode
>>        * for SDIO cards if we need SDIO interrupts to work.
>>        */
>> -     if (mmc->caps & MMC_CAP_SDIO_IRQ) {
>> -             const u32 clken_low_pwr = SDMMC_CLKEN_LOW_PWR << slot->id;
>> -             u32 clk_en_a_old;
>> -             u32 clk_en_a;
>> +     const u32 clken_low_pwr = SDMMC_CLKEN_LOW_PWR << slot->id;
>> +     u32 clk_en_a_old;
>> +     u32 clk_en_a;
>>
>> -             clk_en_a_old = mci_readl(host, CLKENA);
>> +     clk_en_a_old = mci_readl(host, CLKENA);
>>
>> -             if (card->type == MMC_TYPE_SDIO ||
>> -                 card->type == MMC_TYPE_SD_COMBO) {
>> -                     set_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
>> -                     clk_en_a = clk_en_a_old & ~clken_low_pwr;
>> -             } else {
>> -                     clear_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
>> -                     clk_en_a = clk_en_a_old | clken_low_pwr;
>> -             }
>> +     if (card->quirks & MMC_QUIRK_BROKEN_CLK_GATING) {
>> +             set_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
>> +             clk_en_a = clk_en_a_old & ~clken_low_pwr;
>> +     } else {
>> +             clear_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags);
>> +             clk_en_a = clk_en_a_old | clken_low_pwr;
>> +     }
>>
>> -             if (clk_en_a != clk_en_a_old) {
>> -                     mci_writel(host, CLKENA, clk_en_a);
>> -                     mci_send_cmd(slot, SDMMC_CMD_UPD_CLK |
>> -                                  SDMMC_CMD_PRV_DAT_WAIT, 0);
>> -             }
>> +     if (clk_en_a != clk_en_a_old) {
>> +             mci_writel(host, CLKENA, clk_en_a);
>> +             mci_send_cmd(slot, SDMMC_CMD_UPD_CLK |
>> +                             SDMMC_CMD_PRV_DAT_WAIT, 0);
>>       }
>>  }
>>
>>
>
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