Re: [PATCH 1/4] mmc: mediatek: Fix CMD6 timeout issue

[Yong Mao]

On Thu, 2016-12-01 at 10:51 +0100, Ulf Hansson wrote:
> On 8 November 2016 at 07:08, Yong Mao <yong.mao@xxxxxxxxxxxx> wrote:
> > From: yong mao <yong.mao@xxxxxxxxxxxx>
> >
> > When initializing EMMC, after switch to HS400,
> > it will issue CMD6 to change ext_csd, if first CMD6 got CRC
> > error, the repeat CMD6 may get timeout, that's
> > because SDCBSY was cleared by msdc_reset_hw()
> 
> Sorry for the delay!
> 
> We have recently been re-working the sequence for how to deal more
> properly with CMD6 in the mmc core.
> 
> The changes done so far should mostly concern switches to HS and HS
> DDR, but I think you should run a re-test to make sure you still hit
> the same problems.
> 
Happy New Year!

The issue we met is not only just for CMD6, but also for other R1B CMD.
Your new changes does not cover all of these cases.
We would like to make error handle in the core layer to deal with these
issues.

I had submitted a new path ([PATCH v2] Fix CMD6 timeout issue) to you,
please help to review it.
Thanks.


> >
> > Signed-off-by: Yong Mao <yong.mao@xxxxxxxxxxxx>
> > Signed-off-by: Chaotian Jing <chaotian.jing@xxxxxxxxxxxx>
> > ---
> >  drivers/mmc/host/mtk-sd.c |   77 ++++++++++++++++++++++++++++++---------------
> >  1 file changed, 51 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> > index 84e9afc..b29683b 100644
> > --- a/drivers/mmc/host/mtk-sd.c
> > +++ b/drivers/mmc/host/mtk-sd.c
> > @@ -826,6 +826,15 @@ static bool msdc_cmd_done(struct msdc_host *host, int events,
> >         return true;
> >  }
> >
> > +static int msdc_card_busy(struct mmc_host *mmc)
> > +{
> > +       struct msdc_host *host = mmc_priv(mmc);
> > +       u32 status = readl(host->base + MSDC_PS);
> > +
> > +       /* check if data0 is low */
> > +       return !(status & BIT(16));
> > +}
> > +
> >  /* It is the core layer's responsibility to ensure card status
> >   * is correct before issue a request. but host design do below
> >   * checks recommended.
> 
> Hmm. Why?
> 
> I think you should rely on the mmc core to invoke the ->card_busy()
> ops instead. The core knows better when it's needed.
> 
> Perhaps that may also resolve some of these issues for you!?
In my latest patch, msdc_card_busy will not be used in mtk-sd.c
directly. It only can be invoked by ->card_busy() in the mmc core.


> 
> > @@ -835,10 +844,20 @@ static inline bool msdc_cmd_is_ready(struct msdc_host *host,
> >  {
> >         /* The max busy time we can endure is 20ms */
> >         unsigned long tmo = jiffies + msecs_to_jiffies(20);
> > +       u32 count = 0;
> > +
> > +       if (in_interrupt()) {
> > +               while ((readl(host->base + SDC_STS) & SDC_STS_CMDBUSY) &&
> > +                      (count < 1000)) {
> > +                       udelay(1);
> > +                       count++;
> 
> This seems like a bad idea, "busy-wait" in irq context is never a good idea.
Thanks. The modification here is not for the current issue.
I will submit a new patch to discuss with you.


> > +               }
> > +       } else {
> > +               while ((readl(host->base + SDC_STS) & SDC_STS_CMDBUSY) &&
> > +                      time_before(jiffies, tmo))
> > +                       cpu_relax();
> > +       }
> >
> > -       while ((readl(host->base + SDC_STS) & SDC_STS_CMDBUSY) &&
> > -                       time_before(jiffies, tmo))
> > -               cpu_relax();
> >         if (readl(host->base + SDC_STS) & SDC_STS_CMDBUSY) {
> >                 dev_err(host->dev, "CMD bus busy detected\n");
> >                 host->error |= REQ_CMD_BUSY;
> > @@ -846,17 +865,35 @@ static inline bool msdc_cmd_is_ready(struct msdc_host *host,
> >                 return false;
> >         }
> >
> > -       if (mmc_resp_type(cmd) == MMC_RSP_R1B || cmd->data) {
> > -               tmo = jiffies + msecs_to_jiffies(20);
> > -               /* R1B or with data, should check SDCBUSY */
> > -               while ((readl(host->base + SDC_STS) & SDC_STS_SDCBUSY) &&
> > -                               time_before(jiffies, tmo))
> > -                       cpu_relax();
> > -               if (readl(host->base + SDC_STS) & SDC_STS_SDCBUSY) {
> > -                       dev_err(host->dev, "Controller busy detected\n");
> > -                       host->error |= REQ_CMD_BUSY;
> > -                       msdc_cmd_done(host, MSDC_INT_CMDTMO, mrq, cmd);
> > -                       return false;
> > +       if (cmd->opcode != MMC_SEND_STATUS) {
> > +               count = 0;
> > +               /* Consider that CMD6 crc error before card was init done,
> > +                * mmc_retune() will return directly as host->card is null.
> > +                * and CMD6 will retry 3 times, must ensure card is in transfer
> > +                * state when retry.
> > +                */
> > +               tmo = jiffies + msecs_to_jiffies(60 * 1000);
> > +               while (1) {
> > +                       if (msdc_card_busy(host->mmc)) {
> > +                               if (in_interrupt()) {
> > +                                       udelay(1);
> > +                                       count++;
> > +                               } else {
> > +                                       msleep_interruptible(10);
> > +                               }
> > +                       } else {
> > +                               break;
> > +                       }
> > +                       /* Timeout if the device never
> > +                        * leaves the program state.
> > +                        */
> > +                       if (count > 1000 || time_after(jiffies, tmo)) {
> > +                               pr_err("%s: Card stuck in programming state! %s\n",
> > +                                      mmc_hostname(host->mmc), __func__);
> > +                               host->error |= REQ_CMD_BUSY;
> > +                               msdc_cmd_done(host, MSDC_INT_CMDTMO, mrq, cmd);
> > +                               return false;
> > +                       }
> 
> This hole new code is a hack, that shouldn't be needed in the host driver.
> 
> I think we need to investigate and fix the issue in the mmc core
> layer, to make this work for your host driver. That instead of doing a
> work around in the host.
> 
I had already make some modification on the mmc core to resolve these
issues in the latest patch.

> >                 }
> >         }
> >         return true;
> > @@ -1070,18 +1107,6 @@ static int msdc_ops_switch_volt(struct mmc_host *mmc, struct mmc_ios *ios)
> >         return ret;
> >  }
> >
> > -static int msdc_card_busy(struct mmc_host *mmc)
> > -{
> > -       struct msdc_host *host = mmc_priv(mmc);
> > -       u32 status = readl(host->base + MSDC_PS);
> > -
> > -       /* check if any pin between dat[0:3] is low */
> > -       if (((status >> 16) & 0xf) != 0xf)
> > -               return 1;
> > -
> > -       return 0;
> > -}
> > -
> >  static void msdc_request_timeout(struct work_struct *work)
> >  {
> >         struct msdc_host *host = container_of(work, struct msdc_host,
> > --
> > 1.7.9.5
> >
> 
> Kind regards
> Uffe