Re: [PATCH v4] mmc: dw_mmc: force setup bus if active slots exist

[Ziyuan]

On 01/05/2017 03:34 PM, Shawn Lin wrote:
> On 2017/1/5 15:23, Ziyuan Xu wrote:
> > It's necessary to setup bus if any slots are present.
> > - update clock after ctrl reset
> > - if the host has genpd node, we can guarantee the clock is available
> > before starting request. Otherwies, the clock register is reset once
> > power off the pd, and host can't output the active clock during
> > communication.
> >
> > fixes: e9ed8835e990 ("mmc: dw_mmc: add runtime PM callback")
> > Reported-by: Randy Li <randy.li@xxxxxxxxxxxxxx>
> > Signed-off-by: Ziyuan Xu <xzy.xu@xxxxxxxxxxxxxx>
> >
> > ---
> > Hi guys,
> >
> > I found a similar issue on rk3399 platform, which has a genpd node for
> > SD card host. Power off-on pd will reset the registers to a default
> > value (ie. CLKENA), so that the host can't output the active clock
> > during communication.
>
> Indeed, Caesar recently introduced all the genpd for rk3399 platform,
> so we need to restore them.
>
> > So we need to setup bus in rpm resume. It also wraps the update clock
> > behaviour which I did in V3.
> >
> > Thanks,
> > Ziyuan Xu
> >
> >
> > Changes in v4:
> > - update commit message
> > - fix SD host rpm resume can't work
> >
> > Changes in v3:
> > - only reset host with active slot.
> >
> > Changes in v2:
> > - update the commit message
> > - use dw_mci_reset instead of dw_mci_ctrl_reset
> >
> >  drivers/mmc/host/dw_mmc.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index b44306b..b6053b3 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -3354,10 +3354,10 @@ int dw_mci_runtime_resume(struct device *dev)
> >
> >          if (!slot)
> >              continue;
> > -        if (slot->mmc->pm_flags & MMC_PM_KEEP_POWER) {
> > +        if (slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
> >              dw_mci_set_ios(slot->mmc, &slot->mmc->ios);
> > -            dw_mci_setup_bus(slot, true);
> > -        }
> > +        /* Force setup bus to guarantee available clock output */
> > +        dw_mci_setup_bus(slot, true);
>
> So the spamming message about
>
> "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n"
>
> will always be there, right? So you could append a new patch to shut
> up it as I think it's useless no matter for system pm or rpm to print
> it.  How about?

Fine, it's favourable with dev_vdbg if the dw_mmc rpm is enabled.
Hi Jaehoon,
What's your opinion? If you think this patch and shawn's advice are 
acceptable, I will send the v5 patch.

BR
Ziyuan Xu

> >      }
> >
> >      /* Now that slots are all setup, we can enable card detect */