linux-kernel - Re: [PATCH 1/2] mmc: dw_mmc: Cleanup disable of low power mode w/ SDIO interrupts

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Date:	Fri, 18 Oct 2013 13:09:18 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	Chris Ball <cjb@...top.org>, Seungwon Jeon <tgih.jun@...sung.com>,
	James Hogan <james.hogan@...tec.com>,
	Grant Grundler <grundler@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Olof Johansson <olof@...om.net>,
	Sonny Rao <sonnyrao@...omium.org>,
	Bing Zhao <bzhao@...vell.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mmc: dw_mmc: Cleanup disable of low power mode w/
 SDIO interrupts

Jaehoon,

On Fri, Oct 18, 2013 at 2:42 AM, Jaehoon Chung <jh80.chung@...sung.com> wrote:
>> -     clk_en_a = mci_readl(host, CLKENA);
>> +     /*
>> +      * Low power mode will stop the card clock when idle.  According to the
>> +      * 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) {
> mmc->caps & MMC_CAP_SDIO_IRQ?

Wow, that was an embarrassing one.  Thanks.

>> +             const u32 clken_low_pwr = SDMMC_CLKEN_LOW_PWR << slot->id;
>> +             u32 clk_en_a_old;
>> +             u32 clk_en_a;
>>
>> -     if (clk_en_a & clken_low_pwr) {
>> -             mci_writel(host, CLKENA, clk_en_a & ~clken_low_pwr);
>> -             mci_send_cmd(slot, SDMMC_CMD_UPD_CLK |
>> -                          SDMMC_CMD_PRV_DAT_WAIT, 0);
>> +             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;
> When this condition is entered? card->type is always MMC_TYPE_SDIO or MMC_TYPE_SD_COMBO, isn't?

Ugh, that's not intuitive.  This callback is only called for SDIO
cards and not MMC/SD cards?  That means if you plug in an SDIO card
and then eject it and plug in an SD card you won't get to low power.
Hrm.

I dug around a bit and couldn't find a better way to do this and then
I realized that the other user of the init_card() callback has the
same bug, so for the next version of the series I'm proposing a fix
for mmc core to add this for all types.  If you have a better
suggestion, I'm all ears.

-Doug
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