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

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Message-id: <55D1C4CD.4040200@samsung.com>
Date:	Mon, 17 Aug 2015 20:26:05 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Michal Suchanek <hramrach@...il.com>,
	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

On 08/17/2015 02:52 PM, Michal Suchanek wrote:
> 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.

I understood your intention. And i read the comment into mmc/core/quirks.c
I will test SDIO card with this patch. Thanks.

Best Regards,
Jaehoon Chung

> 
> 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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