linux-kernel - Re: [PATCH 1/4] mmc: mmci: avoid fake busy polling

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Message-ID: <CAPDyKFp=AO27hmG9u8JHrRa3JW7RNMbxC8+vMb2y_qGo=mLWQg@mail.gmail.com>
Date:   Wed, 6 Mar 2019 10:49:37 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic BARRE <ludovic.barre@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 1/4] mmc: mmci: avoid fake busy polling

On Wed, 6 Mar 2019 at 10:04, Ludovic BARRE <ludovic.barre@...com> wrote:
>
> Hi Ulf
>
> On 3/6/19 10:00 AM, Ulf Hansson wrote:
> > On Tue, 5 Mar 2019 at 17:10, Ludovic Barre <ludovic.Barre@...com> wrote:
> >>
> >> From: Ludovic Barre <ludovic.barre@...com>
> >>
> >> The busy status bit could occurred even if no busy response is
> >> expected (example cmd11). On sdmmc variant, the busy_detect_flag
> >> reflects inverted value of d0 state, it's sampled at the end of a
> >> CMD response and a second time 2 clk cycles after the CMD response.
> >> To avoid a fake busy, the busy status could be checked and polled
> >> only if the command has RSP_BUSY flag.
> >>
> >> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
> >
> > Before I review this, can you tell what HW you have tested this on?
>
> I tested on stm32mp157c (stm32_sdmmc variant)

Okay, I see. So we need to get this tested for the ux500v2 variant as
well. I try to get some time to do that, soon.

However it seems like you could benefit from having one of those
boards yourself. It would speed up the process, as you wouldn't have
to rely on me doing the test. :-) Is there a chance of you could dig
up some of these old boards from somewhere?

Kind regards
Uffe

>
> >
> > Kind regards
> > Uffe
> >
> >> ---
> >>   drivers/mmc/host/mmci.c | 19 +++++++++++++------
> >>   1 file changed, 13 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> >> index 387ff14..4901b73 100644
> >> --- a/drivers/mmc/host/mmci.c
> >> +++ b/drivers/mmc/host/mmci.c
> >> @@ -1220,12 +1220,13 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
> >>               unsigned int status)
> >>   {
> >>          void __iomem *base = host->base;
> >> -       bool sbc;
> >> +       bool sbc, busy_resp;
> >>
> >>          if (!cmd)
> >>                  return;
> >>
> >>          sbc = (cmd == host->mrq->sbc);
> >> +       busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
> >>
> >>          /*
> >>           * We need to be one of these interrupts to be considered worth
> >> @@ -1239,8 +1240,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
> >>          /*
> >>           * ST Micro variant: handle busy detection.
> >>           */
> >> -       if (host->variant->busy_detect) {
> >> -               bool busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
> >> +       if (busy_resp && host->variant->busy_detect) {
> >>
> >>                  /* We are busy with a command, return */
> >>                  if (host->busy_status &&
> >> @@ -1253,7 +1253,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
> >>                   * that the special busy status bit is still set before
> >>                   * proceeding.
> >>                   */
> >> -               if (!host->busy_status && busy_resp &&
> >> +               if (!host->busy_status &&
> >>                      !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) &&
> >>                      (readl(base + MMCISTATUS) & host->variant->busy_detect_flag)) {
> >>
> >> @@ -1508,6 +1508,7 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
> >>   {
> >>          struct mmci_host *host = dev_id;
> >>          u32 status;
> >> +       bool busy_resp;
> >>          int ret = 0;
> >>
> >>          spin_lock(&host->lock);
> >> @@ -1550,9 +1551,15 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
> >>                  }
> >>
> >>                  /*
> >> -                * Don't poll for busy completion in irq context.
> >> +                * Don't poll for:
> >> +                * -busy completion in irq context.
> >> +                * -no busy response expected.
> >>                   */
> >> -               if (host->variant->busy_detect && host->busy_status)
> >> +               busy_resp = host->cmd ?
> >> +                       !!(host->cmd->flags & MMC_RSP_BUSY) : false;
> >> +
> >> +               if (host->variant->busy_detect &&
> >> +                   (!busy_resp || host->busy_status))
> >>                          status &= ~host->variant->busy_detect_flag;
> >>
> >>                  ret = 1;
> >> --
> >> 2.7.4
> >>