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

[Jaehoon Chung <jh80.chung@samsung.com>]

Hi Doug,

On 10/16/2013 07:39 AM, Doug Anderson wrote:
> In the patch (9623b5b mmc: dw_mmc: Disable low power mode if SDIO
> interrupts are used) I added code that disabled the low power mode of
> dw_mmc when SDIO interrupts are used.  That code worked but always
> felt a little hacky because we ended up disabling low power as a side
> effect of the first enable_sdio_irq() call.  That wouldn't be so bad
> except that disabling low power involves a complicated process of
> writing to the CMD/CMDARG registers and that extra process makes it
> difficult to cleanly the read-modify-write race in
> dw_mci_enable_sdio_irq() (see future patch in the series).
> 
> Change the code to take advantage of the init_card() callback of the
> mmc core to know when an SDIO card has been inserted.  If we've got a
> SDIO card and we're configured to use SDIO Interrupts then turn off
> "low power mode" right away.
> 
> Signed-off-by: Doug Anderson <dianders@chromium.org>
> ---
>  drivers/mmc/host/dw_mmc.c | 68 ++++++++++++++++++++++++-----------------------
>  drivers/mmc/host/dw_mmc.h |  1 +
>  2 files changed, 36 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 0a6a512..1b75816 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -27,6 +27,7 @@
>  #include <linux/stat.h>
>  #include <linux/delay.h>
>  #include <linux/irq.h>
> +#include <linux/mmc/card.h>
>  #include <linux/mmc/host.h>
>  #include <linux/mmc/mmc.h>
>  #include <linux/mmc/sdio.h>
> @@ -822,7 +823,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  
>  		/* enable clock; only low power if no SDIO */
>  		clk_en_a = SDMMC_CLKEN_ENABLE << slot->id;
> -		if (!(mci_readl(host, INTMASK) & SDMMC_INT_SDIO(slot->id)))
> +		if (!test_bit(DW_MMC_CARD_NO_LOW_PWR, &slot->flags))
>  			clk_en_a |= SDMMC_CLKEN_LOW_PWR << slot->id;
>  		mci_writel(host, CLKENA, clk_en_a);
>  
> @@ -1050,27 +1051,37 @@ static int dw_mci_get_cd(struct mmc_host *mmc)
>  	return present;
>  }
>  
> -/*
> - * Disable lower power mode.
> - *
> - * 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.
> - *
> - * This function is fast if low power mode is already disabled.
> - */
> -static void dw_mci_disable_low_power(struct dw_mci_slot *slot)
> +static void dw_mci_init_card(struct mmc_host *mmc, struct mmc_card *card)
>  {
> +	struct dw_mci_slot *slot = mmc_priv(mmc);
>  	struct dw_mci *host = slot->host;
> -	u32 clk_en_a;
> -	const u32 clken_low_pwr = SDMMC_CLKEN_LOW_PWR << slot->id;
>  
> -	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?
> +		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?

Best Regards,
Jaehoon Chung
> +		}
> +
> +		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);
> +		}
>  	}
>  }
>  
> @@ -1082,21 +1093,11 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
>  
>  	/* Enable/disable Slot Specific SDIO interrupt */
>  	int_mask = mci_readl(host, INTMASK);
> -	if (enb) {
> -		/*
> -		 * Turn off low power mode if it was enabled.  This is a bit of
> -		 * a heavy operation and we disable / enable IRQs a lot, so
> -		 * we'll leave low power mode disabled and it will get
> -		 * re-enabled again in dw_mci_setup_bus().
> -		 */
> -		dw_mci_disable_low_power(slot);
> -
> -		mci_writel(host, INTMASK,
> -			   (int_mask | SDMMC_INT_SDIO(slot->id)));
> -	} else {
> -		mci_writel(host, INTMASK,
> -			   (int_mask & ~SDMMC_INT_SDIO(slot->id)));
> -	}
> +	if (enb)
> +		int_mask |= SDMMC_INT_SDIO(slot->id);
> +	else
> +		int_mask &= ~SDMMC_INT_SDIO(slot->id);
> +	mci_writel(host, INTMASK, int_mask);
>  }
>  
>  static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
> @@ -1140,6 +1141,7 @@ static const struct mmc_host_ops dw_mci_ops = {
>  	.get_cd			= dw_mci_get_cd,
>  	.enable_sdio_irq	= dw_mci_enable_sdio_irq,
>  	.execute_tuning		= dw_mci_execute_tuning,
> +	.init_card		= dw_mci_init_card,
>  };
>  
>  static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
> index 6bf24ab..26d4657 100644
> --- a/drivers/mmc/host/dw_mmc.h
> +++ b/drivers/mmc/host/dw_mmc.h
> @@ -227,6 +227,7 @@ struct dw_mci_slot {
>  	unsigned long		flags;
>  #define DW_MMC_CARD_PRESENT	0
>  #define DW_MMC_CARD_NEED_INIT	1
> +#define DW_MMC_CARD_NO_LOW_PWR	2
>  	int			id;
>  	int			last_detect_state;
>  };
>