Re: [PATCH] mmc: mediatek: fix SDIO irq issue

["yong.mao@mediatek.com" <yong.mao@mediatek.com>]

On Wed, 2020-02-12 at 16:29 +0100, Ulf Hansson wrote:
> On Tue, 21 Jan 2020 at 08:21, Yong Mao <yong.mao@mediatek.com> wrote:
> >
> > From: yong mao <yong.mao@mediatek.com>
> >
> > Host controller may lost interrupt in some specail case.
> 
> Please explain a bit more about the special cases. When and how often
> does it happen?
SDIO irq is not triggered by low level, but by falling edge in our
previous IC. This mechanism only have one chance to catch if a SDIO irq
comes within the multiple block transmission. This SDIO irq may easily
lost, because falling edge appears only once within 2 clock after data
transmission is completed. 

> 
> > Add SDIO irq recheck mechanism to make sure all interrupts
> > can be processed immediately.
> >
> > Signed-off-by: Yong Mao <yong.mao@mediatek.com>
> > ---
> >  drivers/mmc/host/mtk-sd.c | 38 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 38 insertions(+)
> >
> > diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> > index 7726dcf..18a1b86 100644
> > --- a/drivers/mmc/host/mtk-sd.c
> > +++ b/drivers/mmc/host/mtk-sd.c
> > @@ -128,6 +128,7 @@
> >  #define MSDC_PS_CDSTS           (0x1 << 1)     /* R  */
> >  #define MSDC_PS_CDDEBOUNCE      (0xf << 12)    /* RW */
> >  #define MSDC_PS_DAT             (0xff << 16)   /* R  */
> > +#define MSDC_PS_DATA1           (0x1 << 17)    /* R  */
> >  #define MSDC_PS_CMD             (0x1 << 24)    /* R  */
> >  #define MSDC_PS_WP              (0x1 << 31)    /* R  */
> >
> > @@ -361,6 +362,7 @@ struct msdc_save_para {
> >
> >  struct mtk_mmc_compatible {
> >         u8 clk_div_bits;
> > +       bool recheck_sdio_irq;
> >         bool hs400_tune; /* only used for MT8173 */
> >         u32 pad_tune_reg;
> >         bool async_fifo;
> > @@ -436,6 +438,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt8135_compat = {
> >         .clk_div_bits = 8,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE,
> >         .async_fifo = false,
> > @@ -448,6 +451,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt8173_compat = {
> >         .clk_div_bits = 8,
> > +       .recheck_sdio_irq = true,
> >         .hs400_tune = true,
> >         .pad_tune_reg = MSDC_PAD_TUNE,
> >         .async_fifo = false,
> > @@ -460,6 +464,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt8183_compat = {
> >         .clk_div_bits = 12,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE0,
> >         .async_fifo = true,
> > @@ -472,6 +477,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt2701_compat = {
> >         .clk_div_bits = 12,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE0,
> >         .async_fifo = true,
> > @@ -484,6 +490,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt2712_compat = {
> >         .clk_div_bits = 12,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE0,
> >         .async_fifo = true,
> > @@ -496,6 +503,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt7622_compat = {
> >         .clk_div_bits = 12,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE0,
> >         .async_fifo = true,
> > @@ -508,6 +516,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt8516_compat = {
> >         .clk_div_bits = 12,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE0,
> >         .async_fifo = true,
> > @@ -518,6 +527,7 @@ struct msdc_host {
> >
> >  static const struct mtk_mmc_compatible mt7620_compat = {
> >         .clk_div_bits = 8,
> > +       .recheck_sdio_irq = false,
> >         .hs400_tune = false,
> >         .pad_tune_reg = MSDC_PAD_TUNE,
> >         .async_fifo = false,
> > @@ -1007,6 +1017,30 @@ static int msdc_auto_cmd_done(struct msdc_host *host, int events,
> >         return cmd->error;
> >  }
> >
> > +/**
> > + * msdc_recheck_sdio_irq - recheck whether the SDIO irq is lost
> > + *
> > + * Host controller may lost interrupt in some special case.
> > + * Add SDIO irq recheck mechanism to make sure all interrupts
> > + * can be processed immediately
> > + *
> > + */
> > +static void msdc_recheck_sdio_irq(struct msdc_host *host)
> > +{
> > +       u32 reg_int, reg_inten, reg_ps;
> > +
> > +       if ((host->mmc->caps & MMC_CAP_SDIO_IRQ)) {
> > +               reg_inten = readl(host->base + MSDC_INTEN);
> > +               if (reg_inten & MSDC_INTEN_SDIOIRQ) {
> > +                       reg_int = readl(host->base + MSDC_INT);
> > +                       reg_ps = readl(host->base + MSDC_PS);
> > +                       if (!((reg_int & MSDC_INT_SDIOIRQ) ||
> > +                             (reg_ps & MSDC_PS_DATA1)))
> 
> This looks a bit unnecessary complicated and there are more
> parentheses than needed.
  Thanks. We will remove unnecessary parentheses in the next version.

> 
> I am also wondering about the logic. This looks like you want to
> signal an SDIO IRQ when both MSDC_INT_SDIOIRQ and MSDC_PS_DATA1 are
> cleared. Is that really correct?
Yes. This can make sure every SW SDIO irq is really lost by HW.
And also make sure it is not fake irq.

> 
> Moreover, this means that you will be polling the registers for each
> every request you complete. This sounds quite inefficient and I wonder
> if it can be done more seldom, 
Yes. You are right. Re-check will be invoked often.
But registers access does not cost more time.

> perhaps via a timer event instead.
This timer will be alive until the SDIO card is removed.
It is very similar with polling mechanism in sdio_irq_thread.
Because this patch is only for previous IC(Our new IC does not have
this issue), we don't want make too many changes in mtk-sd.c.
If there is some other simple solution, we will update in the next version.


>  And,
> what if there is no request for a while, then this means the re-check
> doesn't gets to run. Could that be a problem?
The SDIO irq in this case can be catch by HW correctly.

> 
> > +                               sdio_signal_irq(host->mmc);
> 
> Before calling sdio_signal_irq(), the SDIO IRQ needs to be temporarily
> disabled. In other words, looks like you should be calling
> __msdc_enable_sdio_irq(0) from here as well.
Yes. You are right.
We will update it in next version.

> 
> > +               }
> > +       }
> > +}
> > +
> >  static void msdc_track_cmd_data(struct msdc_host *host,
> >                                 struct mmc_command *cmd, struct mmc_data *data)
> >  {
> > @@ -1035,6 +1069,8 @@ static void msdc_request_done(struct msdc_host *host, struct mmc_request *mrq)
> >         if (host->error)
> >                 msdc_reset_hw(host);
> >         mmc_request_done(host->mmc, mrq);
> > +       if (host->dev_comp->recheck_sdio_irq)
> > +               msdc_recheck_sdio_irq(host);
> >  }
> >
> >  /* returns true if command is fully handled; returns false otherwise */
> > @@ -1393,6 +1429,8 @@ static void __msdc_enable_sdio_irq(struct msdc_host *host, int enb)
> >         if (enb) {
> >                 sdr_set_bits(host->base + MSDC_INTEN, MSDC_INTEN_SDIOIRQ);
> >                 sdr_set_bits(host->base + SDC_CFG, SDC_CFG_SDIOIDE);
> > +               if (host->dev_comp->recheck_sdio_irq)
> > +                       msdc_recheck_sdio_irq(host);
> >         } else {
> >                 sdr_clr_bits(host->base + MSDC_INTEN, MSDC_INTEN_SDIOIRQ);
> >                 sdr_clr_bits(host->base + SDC_CFG, SDC_CFG_SDIOIDE);
> > --
> > 1.9.1
> 
> Kind regards
> Uffe