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

[Seungwon Jeon <tgih.jun@samsung.com>]

On Friday, August 24, 2012, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> 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
If you know a point in time, we can reproduce it.

> 
> 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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