RE: [PATCH 1/3] mmc: core: do power-off with resume failure

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On Mon, August 26, 2013, Ulf Hansson wrote:
> On 26 August 2013 08:39, Seungwon Jeon <tgih.jun@xxxxxxxxxxx> wrote:
> > On Friday, August 23, 2013, Ulf Hansson wrote:
> >> On 21 August 2013 14:42, Seungwon Jeon <tgih.jun@xxxxxxxxxxx> wrote:
> >> > Currently there is no mmc_power_off() when resume failed.
> >> > Somehow, state from mmc_power_on() will be kept. This change
> >> > makes a pair with its use in case of failure.
> >>
> >> Hi Seungwon,
> >>
> >> To be safe, we can not power off, even if a resume failures. The
> >> reason is that the bus/card/host is still available for sending
> >> commands to it and those will then likely hang since IP controllers
> >> internal registers is configured for "power off" state.
> > Generally when host drivers get MMC_POWER_OFF, host doesn't gate clock for host running.
> > MMC_POWER_ON/OFF is related to card side. So, I guess hanging isn't expected because host is kept
> ready.
> 
> At least for mmci host driver a hang may happen. Internal IP registers
> needs to be set properly as done for MMC_POWER_ON mode, otherwise a
> cmd can not be sent to the card without a potential hang, forever
> waiting for an interrupt.
I looked into the set_ios function of mmci host.
Power for I/O bus lines are controlled there. Then unexpected occurrence from host may be possible.
Host can raise interrupt though.
Ok.

Thanks,
Seungwon Jeon

> 
> I would be surprised if similar issues could not occur for other host
> controllers/drivers.
> 
> Kind regards
> Ulf Hansson
> 
> >
> >>
> >> Instead, we must leave the power off to be handled from the next
> >> rescan work when the card is no longer properly "detected". For
> >> NONREMOVABLE we will instead at error path try to do a
> >> "power_restore_host".
> > It might be needed graceful error handling.
> > Ok, I'll consider further.
> >
> > Thanks,
> > Seungwon Jeon
> >
> >>
> >> Kind regards
> >> Ulf Hansson
> >>
> >>
> >> >
> >> > Signed-off-by: Seungwon Jeon <tgih.jun@xxxxxxxxxxx>
> >> > ---
> >> >  drivers/mmc/core/mmc.c  |    3 +++
> >> >  drivers/mmc/core/sd.c   |    3 +++
> >> >  drivers/mmc/core/sdio.c |    3 +++
> >> >  3 files changed, 9 insertions(+), 0 deletions(-)
> >> >
> >> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> >> > index 6d02012..704a561 100644
> >> > --- a/drivers/mmc/core/mmc.c
> >> > +++ b/drivers/mmc/core/mmc.c
> >> > @@ -1536,6 +1536,9 @@ static int mmc_resume(struct mmc_host *host)
> >> >         mmc_power_up(host);
> >> >         mmc_select_voltage(host, host->ocr);
> >> >         err = mmc_init_card(host, host->ocr, host->card);
> >> > +       if (err)
> >> > +               mmc_power_off(host);
> >> > +
> >> >         mmc_release_host(host);
> >> >
> >> >         return err;
> >> > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> >> > index 176d125..2690ae1 100644
> >> > --- a/drivers/mmc/core/sd.c
> >> > +++ b/drivers/mmc/core/sd.c
> >> > @@ -1099,6 +1099,9 @@ static int mmc_sd_resume(struct mmc_host *host)
> >> >         mmc_power_up(host);
> >> >         mmc_select_voltage(host, host->ocr);
> >> >         err = mmc_sd_init_card(host, host->ocr, host->card);
> >> > +       if (err)
> >> > +               mmc_power_off(host);
> >> > +
> >> >         mmc_release_host(host);
> >> >
> >> >         return err;
> >> > diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> >> > index 80d89cf..8c65669 100644
> >> > --- a/drivers/mmc/core/sdio.c
> >> > +++ b/drivers/mmc/core/sdio.c
> >> > @@ -1033,6 +1033,9 @@ static int mmc_sdio_resume(struct mmc_host *host)
> >> >                 }
> >> >         }
> >> >
> >> > +       if (err && !mmc_card_keep_power(host))
> >> > +               mmc_power_off(host);
> >> > +
> >> >         host->pm_flags &= ~MMC_PM_KEEP_POWER;
> >> >         return err;
> >> >  }
> >> > --
> >> > 1.7.0.4
> >> >
> >> >
> >> > --
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