Re: [PATCH 1/3] mmc:sunxi-mmc:add support on discrete device power supply

["michael@allwinnertech.com" <michael@allwinnertech.com>]

> On Fri, 31 Dec 2021 at 09:28, michael@allwinnertech.com
> <michael@allwinnertech.com> wrote:
> >
> > > From: Ulf Hansson
> > > Date: 2021-12-29 00:49
> > > To: Michael Wu
> > > CC: mripard; wens; samuel; andre.przywara; jernej.skrabec; linux-mmc; linux-arm-kernel; linux-sunxi; linux-kernel
> > > Subject: Re: [PATCH 1/3] mmc:sunxi-mmc:add support on discrete device power supply
> > > On Wed, 22 Dec 2021 at 04:07, Michael Wu <michael@allwinnertech.com> wrote:
> > > >
> > > > Because some platform has no regulator, only use discrete devices
> > > > to supply power,For this situation, to use sd/mmc card, we add ocr manually
> > > >
> > > > Signed-off-by: Michael Wu <michael@allwinnertech.com>
> > > > ---
> > > >  drivers/mmc/host/sunxi-mmc.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> > > > index 2702736a1c57..afeefead6501 100644
> > > > --- a/drivers/mmc/host/sunxi-mmc.c
> > > > +++ b/drivers/mmc/host/sunxi-mmc.c
> > > > @@ -1300,6 +1300,14 @@ static int sunxi_mmc_resource_request(struct sunxi_mmc_host *host,
> > > >         if (ret)
> > > >                 return ret;
> > > >
> > > > +       /**
> > > > +        * Some platforms has no regulator. Discrete devices are used instead.
> > > > +        * To support sd/mmc card, we need to add ocr manually.
> > > > +        */
> > > > +       if (!host->mmc->ocr_avail)
> > > > +               host->mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
> > > > +
> > >
> > > Rather than doing this, I suggest you hook up a fixed vmmc regulator in the DTS.
> > >
> > > Nevertheless, it seems reasonable to check that the ocr_avail gets set
> > > up correctly. And if it doesn't, perhaps we should print a warning and
> > > return an error code.
> > >
> > > > +
> > > >         host->reg_base = devm_platform_ioremap_resource(pdev, 0);
> > > >         if (IS_ERR(host->reg_base))
> > > >                 return PTR_ERR(host->reg_base);
> > >
> > > Kind regards
> > > Uffe
> >
> > Dear Uffe,
> > Thanks for your suggestion. It is a better solution.
> > I've modified my patch. Please check if it's reasonable. If it is, I'll re-sumbit it later.
> >
> > ---
> > Subject: [PATCH v2] mmc: sunxi-mmc: check ocr_avail on resource request
> >
> > Some platforms have no regulator, discrete power devices are used instead.
> > However, sunxi_mmc_probe does not catch this exception when regulator is
> > absent in DTS. This leads to sd or eMMC init failure.
> > To solve this, a fixed vmmc regulator must be hooked up in DTS, like this:
> > reg_dummy_vmmc: dummy_vmmc {
> >         compatible = "regulator-fixed";
> >         regulator-name = "dummy-vmmc";
> >         regulator-min-microvolt = <500000>;
> >         regulator-max-microvolt = <3500000>;
> 
> The min/max should be set to the same value as you can't really change
> the voltage levels.
> 
> If you know the voltage level that is supplied for your platform, then
> state this value - otherwise I would suggest picking 3.3V, which is
> rather commonly used for MMC/SD.

Okay. The supplied voltage is 2.7V~3.6V. l'll correct the min/max value to 3.3V:

        regulator-min-microvolt = <3300000>;
        regulator-max-microvolt = <3300000>;

> > };
> > mmc0:mmc@4020000 {
> >         compatible = "allwinner,sun50i-a100-emmc";
> >         device_type = "mmc0";
> >         vmmc-supply = <&reg_dummy_vmmc>;
> > }
> > In this patch, we print an error message and abort the probe process if
> > the regulator is not specified in DTS.
> >
> > Signed-off-by: Michael Wu <michael@allwinnertech.com>
> > ---
> >
> > diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> > index 2702736..0da74bd 100644
> > --- a/drivers/mmc/host/sunxi-mmc.c
> > +++ b/drivers/mmc/host/sunxi-mmc.c
> > @@ -1300,6 +1300,11 @@
> >         if (ret)
> >                 return ret;
> >
> > +       if (!host->mmc->ocr_avail) {
> > +               dev_err(&pdev->dev, "Could not get mmc regulator\n");
> > +               return -EINVAL;
> > +       }
> > +
> >         host->reg_base = devm_platform_ioremap_resource(pdev, 0);
> >         if (IS_ERR(host->reg_base))
> >                 return PTR_ERR(host->reg_base);
> >
> > Best Regards,
> > Michael Wu
> 
> Yep, this looks good to me!
> 
> Kind regards
> Uffe

I'll submit the patch once I get back to work. Thanks for your effort and happy new year :)

Best Regards,
Michael Wu
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