Re: [PATCH V2 3/5] mmc: mmci: fix clear of busy detect status

[Ludovic BARRE]

hi Ulf

On 5/27/19 8:17 PM, Ulf Hansson wrote:
> On Fri, 26 Apr 2019 at 09:46, Ludovic Barre <ludovic.Barre@xxxxxx> wrote:
> > From: Ludovic Barre <ludovic.barre@xxxxxx>
> >
> > The "busy_detect_flag" is used to read/clear busy value of
> > mmci status. The "busy_detect_mask" is used to manage busy irq of
> > mmci mask.
> > For sdmmc variant, the 2 properties have not the same offset.
> > To clear the busyd0 status bit, we must add busy detect flag,
> > the mmci mask is not enough.
> >
> > Signed-off-by: Ludovic Barre <ludovic.barre@xxxxxx>
>
> Ludovic, again, apologies for the delay.
>
> > ---
> >   drivers/mmc/host/mmci.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> > index a040f54..3cd52e8 100644
> > --- a/drivers/mmc/host/mmci.c
> > +++ b/drivers/mmc/host/mmci.c
> > @@ -1517,7 +1517,8 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
> >                   * to make sure that both start and end interrupts are always
> >                   * cleared one after the other.
> >                   */
> > -               status &= readl(host->base + MMCIMASK0);
> > +               status &= readl(host->base + MMCIMASK0) |
> > +                       host->variant->busy_detect_flag;
>
> I think this is not entirely correct, because it would mean we check
> for busy even if we haven't unmasked the busy IRQ via the
> variant->busy_detect_mask.

if the variant is busy_detect false:
 => no problem because the busy_detect_flag or busy_detect_mask is not
    defined.

if variant is busy_detect true:
the busy handle is split in 3 steps (see mmci_cmd_irq):
step 1: detection of busy line => unmasked the busy irq end
step 2: in busy wait => ignore cmd irq while current busy flag is
enabled.
step 3: end of busy => clear and mask busy irq

To detect the first step (see mmci_cmd_irq: which unmasks the busy irq)
we need to know the current busy state. Actually, the status register is
re-read in mmci_cmd_irq, why not used the status read in mmci_irq and in
parameter ?

Regards,
Ludo

> I suggest to store a new bool in the host (call it
> "busy_detect_unmasked" or whatever makes sense to you), to track
> whether we have unmasked the busy IRQ or not. Then take this flag into
> account, before ORing the value of host->variant->busy_detect_flag,
> according to above.
>
> >                  if (host->variant->busy_detect)
> >                          writel(status & ~host->variant->busy_detect_mask,
> >                                 host->base + MMCICLEAR);
> > --
> > 2.7.4
>
> Kind regards
> Uffe