Re: [PATCH] mmc: dw_mmc: change to use recommended reset procedure

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

Hi, Sonny.

I have checked the Synopsys TRM..

On 05/09/2014 10:34 AM, Sonny Rao wrote:
> On Thu, May 8, 2014 at 6:15 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> On 05/08/2014 06:40 PM, Yuvaraj Kumar wrote:
>>> Any comments on this patch?
>>>
>>> On Wed, Mar 26, 2014 at 5:16 PM, Yuvaraj Kumar C D <yuvaraj.cd@gmail.com> wrote:
>>>> From: Sonny Rao <sonnyrao@chromium.org>
>>>>
>>>> This patch changes the fifo reset code to follow the reset procedure
>>>> outlined in the documentation of Synopsys  Mobile storage host databook
>>>> 7.2.13.
>>>> Without this patch, we could able to see eMMC was not detected after
>>>> multiple reboots due to driver hangs while eMMC tuning for HS200.
>>>>
>>>> Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
>>>> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.org>
>>>> ---
>>>>  drivers/mmc/host/dw_mmc.c |   48 ++++++++++++++++++++++++++++++++++++++++++++-
>>>>  drivers/mmc/host/dw_mmc.h |    1 +
>>>>  2 files changed, 48 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>>> index 32dd81d..1d77431 100644
>>>> --- a/drivers/mmc/host/dw_mmc.c
>>>> +++ b/drivers/mmc/host/dw_mmc.c
>>>> @@ -2220,7 +2220,53 @@ static inline bool dw_mci_fifo_reset(struct dw_mci *host)
>>>>                 host->sg = NULL;
>>>>         }
>>>>
>>>> -       return dw_mci_ctrl_reset(host, SDMMC_CTRL_FIFO_RESET);
>>>> +       /*
>>>> +        * The recommended method for resetting is to always reset the
>>>> +        * controller and the fifo, but differs slightly depending on the mode.
>>>> +        * Note that this doesn't handle the "generic DMA" (not IDMAC) case.
>>>> +        */
>>
>> "not IDMAC" is confused..
>>
> 
> The documentation describes three different possible modes.  There's a
> mode that doesn't use IDMAC but still does DMA.  But as far as I can
> tell this driver doesn't support that way.  We can just remove that
> wording if it's confusing.
> 
>>>> +       if (dw_mci_ctrl_reset(host, SDMMC_CTRL_RESET | SDMMC_CTRL_FIFO_RESET)) {
>>>> +               unsigned long timeout = jiffies + msecs_to_jiffies(500);
>>>> +               u32 status, rint;
>>>> +
>>>> +               /* if using dma we wait for dma_req to clear */
>>>> +               if (host->using_dma) {
>>>> +                       do {
>>>> +                               status = mci_readl(host, STATUS);
>>>> +                               if (!(status & SDMMC_STATUS_DMA_REQ))
>>>> +                                       break;
>>>> +                               cpu_relax();
>>>> +                       } while (time_before(jiffies, timeout));
>>>> +
>>>> +                       if (status & SDMMC_STATUS_DMA_REQ)
>>>> +                               dev_err(host->dev,
>>>> +                                       "%s: Timeout waiting for dma_req to "
>>>> +                                       "clear during reset", __func__);
>>>> +
>>>> +                       /* when using DMA next we reset the fifo again */
>>>> +                       dw_mci_ctrl_reset(host, SDMMC_CTRL_FIFO_RESET);
>>>> +               }
>>>> +               /*
>>>> +                * In all cases we clear the RAWINTS register to clear any
>>>> +                * interrupts.
>>>> +                */
>>>> +               rint = mci_readl(host, RINTSTS);
>>>> +               rint = rint & (~mci_readl(host, MINTSTS));
you use the "status or temp" instead of rint. (you can reuse the variable.)
And can use "status &= ~mci_readl(host,MINTSTS);"

>>
>> Just clear the RINTSTS register? why do you add these?
>>
> 
> This will look at what is not masked, and only clear those bits.
Well, i known if clear the RINTSTS register, 
recommended to use "0xfffffff" and set the value for interrupt.

> 
>>>> +               if (rint)
>>>> +                       mci_writel(host, RINTSTS, rint);
>>>> +
>>>> +       } else
>>>> +               dev_err(host->dev, "%s: Reset bits didn't clear", __func__);
>>
>> Just display the error log? I didn't understand this.
>> If you displayed the error log, then it needs to return the error value.
>>
>>>> +
>>>> + #ifdef CONFIG_MMC_DW_IDMAC
>>>> +       /* It is also recommended that we reset and reprogram idmac */
>>>> +       dw_mci_idmac_reset(host);
>>>> + #endif
>>>> +
>>>> +       /* After a CTRL reset we need to have CIU set clock registers  */
>>>> +       mci_send_cmd(host->cur_slot, SDMMC_CMD_UPD_CLK, 0);

Well, why do you send the clock update command?
I didn't see that update the value related with clock.

Best Regards,
Jaehoon Chung

>>>> +
>>>> +       return true;
>>>>  }
>>>>
>>>>  static inline bool dw_mci_ctrl_all_reset(struct dw_mci *host)
>>>> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
>>>> index 738fa24..037e47a 100644
>>>> --- a/drivers/mmc/host/dw_mmc.h
>>>> +++ b/drivers/mmc/host/dw_mmc.h
>>>> @@ -129,6 +129,7 @@
>>>>  #define SDMMC_CMD_INDX(n)              ((n) & 0x1F)
>>>>  /* Status register defines */
>>>>  #define SDMMC_GET_FCNT(x)              (((x)>>17) & 0x1FFF)
>>>> +#define SDMMC_STATUS_DMA_REQ           BIT(31)
>>>>  /* FIFOTH register defines */
>>>>  #define SDMMC_SET_FIFOTH(m, r, t)      (((m) & 0x7) << 28 | \
>>>>                                          ((r) & 0xFFF) << 16 | \
>>>> --
>>>> 1.7.10.4
>>>>
>>>
>>
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