Re: [PATCH 2/2] mmc: dw_mmc: add resets support to dw_mci_parse_dt()

[Shawn Lin]

在 2016/3/4 11:27, zhangfei 写道:
> On 03/03/2016 10:00 AM, Shawn Lin wrote:
> > Hi Guodong,
> >
> > On 2016/3/3 9:33, Guodong Xu wrote:
> > > With this, user can add a 'resets' property into dw_mmc dts
> > > node, and when driver probe and parse_dt, it will call
> > > reset APIs to reset dw_mmc host controller.
> > >
> > > Please also refer to Documentation/devicetree/bindings/reset/reset.txt
> >
> > I have no hard objection for this patch, but I'd rather not add it
> > unless we actually need it. Could you elaborate more about any futher
> > actions you will take if it's applied(i.e: deal with some unrecoverable
> > broken case)?  If we just reset the controller while probing, actually I
> > can't find any problems without it based on tons of my reboot test.
>
> mmc register maybe abnormal state, if mmc is used in uefi, like boot
> from emmc.
> So we need reset mmc register when kernel boot up, instead of assuming
> mmc is in clean state.
> Next step is adding reset node in dts for drivers/mmc/host/dw_mmc-k3.c
> as reset driver is already there.

Fair enough. Thanks for explaining.

> > > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > > index 242f9a0..d3a7376 100644
> > > --- a/drivers/mmc/host/dw_mmc.c
> > > +++ b/drivers/mmc/host/dw_mmc.c
> > > @@ -2878,6 +2878,13 @@ static struct dw_mci_board
> > > *dw_mci_parse_dt(struct dw_mci *host)
> > >       if (!pdata)
> > >           return ERR_PTR(-ENOMEM);
> > >
> > > +    /* find reset controller when exist */
> > > +    pdata->rstc = devm_reset_control_get_optional(dev, NULL);
> > > +    if (IS_ERR(pdata->rstc))
> > > +        pdata->rstc = NULL;
> > > +    else
> > > +        reset_control_deassert(pdata->rstc);
> > > +
> >
> > if the PTR_ERR(pdata->rstc) is -EPROBE_DEFER, should we defer probing
> > the driver?
> Yes, good catch.
>
> Thanks


--
Best Regards
Shawn Lin