Re: [PATCH 2/5] mmc: dw-mmc: ensure that the card is not busy when changing clock.

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

Hi Seungwon,

On 08/24/2012 12:55 PM, Seungwon Jeon wrote:
> Hi Jaehoon,
> 
> On Thursday, August 23, 2012, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> To avoid glitches in the card clock output,
>> need to check whether card is busy or not.
> Could you describe the problem more?
synopsys spec is mentioned. (7.1 Software/Hardware Restrictions)
"Before disabling clock, ensure that card is not busy due to any previous data command."

> In which situation did you meet this?
At specific board, i found the problem that didn't inform ciu.
(It didn't produce always.)
At that time, i checked the status register whether card is busy or not.
(Start bit of CMD register is cleared, but card is busy.)
Current code didn't check the card status. Just check whether the start-bit cleared.
host regard that command is completed, will send the next command.
But next command didn't issue because Card is busy.
This patch can prevent this situation.

If you have any comment or opinion, please let me know. it's great help to me

Best Regards,
Jaehoon Chung
> 
> Thanks,
> Seungwon Jeon
>>
>> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>> ---
>>  drivers/mmc/host/dw_mmc.c |   30 ++++++++++++++++++++++++------
>>  drivers/mmc/host/dw_mmc.h |    1 +
>>  2 files changed, 25 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 36f98c0..8bef3c2 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -623,6 +623,27 @@ static void mci_send_cmd(struct dw_mci_slot *slot, u32 cmd, u32 arg)
>>  		cmd, arg, cmd_status);
>>  }
>>
>> +static void dw_mci_inform_ciu(struct dw_mci_slot *slot)
>> +{
>> +	struct dw_mci *host = slot->host;
>> +	unsigned long timeout = jiffies + msecs_to_jiffies(500);
>> +	u32 ctrl, status;
>> +
>> +	do {
>> +		status = mci_readl(host, STATUS);
>> +		if (!(status & SDMMC_DATA_BUSY))
>> +			break;
>> +		ctrl = mci_readl(host, CTRL);
>> +		ctrl |= SDMMC_CTRL_RESET;
>> +		mci_writel(host, CTRL, ctrl);
>> +	} while (time_before(jiffies, timeout));
>> +
>> +	if (status & SDMMC_DATA_BUSY)
>> +		dev_err(&slot->mmc->class_dev,"Card is busy..!\n");
>> +
>> +	mci_send_cmd(slot, SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> +}
>> +
>>  static void dw_mci_setup_bus(struct dw_mci_slot *slot)
>>  {
>>  	struct dw_mci *host = slot->host;
>> @@ -650,15 +671,13 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot)
>>  		mci_writel(host, CLKSRC, 0);
>>
>>  		/* inform CIU */
>> -		mci_send_cmd(slot,
>> -			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> +		dw_mci_inform_ciu(slot);
>>
>>  		/* set clock to desired speed */
>>  		mci_writel(host, CLKDIV, div);
>>
>>  		/* inform CIU */
>> -		mci_send_cmd(slot,
>> -			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> +		dw_mci_inform_ciu(slot);
>>
>>  		/* enable clock; only low power if no SDIO */
>>  		clk_en_a = SDMMC_CLKEN_ENABLE << slot->id;
>> @@ -667,8 +686,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot)
>>  		mci_writel(host, CLKENA, clk_en_a);
>>
>>  		/* inform CIU */
>> -		mci_send_cmd(slot,
>> -			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> +		dw_mci_inform_ciu(slot);
>>
>>  		host->current_speed = slot->clock;
>>  	}
>> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
>> index 15c27e1..b6a1a78 100644
>> --- a/drivers/mmc/host/dw_mmc.h
>> +++ b/drivers/mmc/host/dw_mmc.h
>> @@ -127,6 +127,7 @@
>>  #define SDMMC_CMD_INDX(n)		((n) & 0x1F)
>>  /* Status register defines */
>>  #define SDMMC_GET_FCNT(x)		(((x)>>17) & 0x1FFF)
>> +#define SDMMC_DATA_BUSY			BIT(9)
>>  /* Internal DMAC interrupt defines */
>>  #define SDMMC_IDMAC_INT_AI		BIT(9)
>>  #define SDMMC_IDMAC_INT_NI		BIT(8)
>> --
>> 1.7.4.1
>> --
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