Re: [PATCH v2 1/2] mmc: dw_mmc: fix bug that cause 'Timeout sending command'

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

Hi, Addy.

On 02/09/2015 04:25 PM, Addy Ke wrote:
> Because of some uncertain factors, such as worse card or worse hardware,
> DAT[3:0](the data lines) may be pulled down by card, and mmc controller
> will be in busy state. This should not happend when mmc controller
> send command to update card clocks. If this happends, mci_send_cmd will
> be failed and we will get 'Timeout sending command', and then system will
> be blocked. To avoid this, we need reset mmc controller.
> 
> Signed-off-by: Addy Ke <addy.ke@rock-chips.com>
> ---
>  drivers/mmc/host/dw_mmc.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 4d2e3c2..b0b57e3 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -100,6 +100,7 @@ struct idmac_desc {
>  };
>  #endif /* CONFIG_MMC_DW_IDMAC */
>  
> +static int dw_mci_card_busy(struct mmc_host *mmc);
>  static bool dw_mci_reset(struct dw_mci *host);
>  static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
>  
> @@ -888,6 +889,31 @@ static void mci_send_cmd(struct dw_mci_slot *slot, u32 cmd, u32 arg)
>  		cmd, arg, cmd_status);
>  }
>  
> +static void dw_mci_wait_busy(struct dw_mci_slot *slot)
> +{
> +	struct dw_mci *host = slot->host;
> +	unsigned long timeout = jiffies + msecs_to_jiffies(500);
> +
> +	do {
> +		if (!dw_mci_card_busy(slot->mmc))
> +			return;
> +		cpu_relax();
> +	} while (time_before(jiffies, timeout));
> +
> +	dev_err(host->dev, "Data busy (status %#x)\n",
> +		mci_readl(slot->host, STATUS));
> +
> +	/*
> +	 * Data busy, this should not happend when mmc controller send command
> +	 * to update card clocks in non-volt-switch state. If it happends, we
> +	 * should reset controller to avoid getting "Timeout sending command".
> +	 */
> +	dw_mci_ctrl_reset(host, SDMMC_CTRL_ALL_RESET_FLAGS);

If reset is failed, then dw_mci_ctrl_reset should return "false".

	ret = dw_mci_ctrl_reset();

	WARN_ON(!ret || dw_mci_card_busy(slot->mmc));

Is it right?

In my experiment, if reset is failed or card is busy, eMMC can't work anymore..right?
I think this patch is reasonable to prevent blocking issue.

Best Regards,
Jaehoon Chung


> +
> +	/* Fail to reset controller or still data busy, WARN_ON! */
> +	WARN_ON(dw_mci_card_busy(slot->mmc));
> +}
> +
>  static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  {
>  	struct dw_mci *host = slot->host;
> @@ -899,6 +925,8 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  	/* We must continue to set bit 28 in CMD until the change is complete */
>  	if (host->state == STATE_WAITING_CMD11_DONE)
>  		sdmmc_cmd_bits |= SDMMC_CMD_VOLT_SWITCH;
> +	else
> +		dw_mci_wait_busy(slot);
>  
>  	if (!clock) {
>  		mci_writel(host, CLKENA, 0);
>