Re: [PATCH 1/6] dt-bindings: mmc: sdhci-of-dwcmhsc: Add T-Head TH1520 support

Guo Ren
2023-09-23T08:10:37Z

On Fri, Sep 22, 2023 at 11:18 PM Drew Fustini <dfustini@baylibre.com> wrote:
>
> On Fri, Sep 22, 2023 at 10:57:36AM +0100, Conor Dooley wrote:
> > Hey Drew,
> >
> > On Thu, Sep 21, 2023 at 06:49:48PM -0700, Drew Fustini wrote:
> > > Add compatible value for the T-Head TH1520 dwcmshc controller and add
> > > thead,phy-pull-up property.
> > >
> > > Signed-off-by: Drew Fustini <dfustini@baylibre.com>
> > > ---
> > > Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml b/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > > index a43eb837f8da..46b768d46712 100644
> > > --- a/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > > +++ b/Documentation/devicetree/bindings/mmc/snps,dwcmshc-sdhci.yaml
> > > @@ -19,6 +19,7 @@ properties:
> > > - rockchip,rk3568-dwcmshc
> > > - rockchip,rk3588-dwcmshc
> > > - snps,dwcmshc-sdhci
> > > + - thead,th1520-dwcmshc
> > >
> > > reg:
> > > maxItems: 1
> > > @@ -60,6 +61,9 @@ properties:
> > > description: Specify the number of delay for tx sampling.
> > > $ref: /schemas/types.yaml#/definitions/uint8
> > >
> > > + thead,phy-pull-up:
> > > + description: Enable weak pull-up on PHY pads
> > > + type: boolean
> >
> > Why is the weak pull-up required? How would the dts author know if they
> > need to use this property?
>
> This is a good question, and I don't have a good reason beyond it is
> what the vendor SDK was doing.
>
> There are only two boards right now using the TH1520 that I know of.
> Both the LPi4a [1] and the Ahead [2] have the pull-up property set on
> all the mmc controller nodes their downstream device trees.
>
> Rob suggested on #devicetree that it would be simpler to just enable it
> in the driver and disable support when needed. I like this idea as it
> will simplify this binding patch and the code in the driver patch.
It's for the PHY debug. You could directly remove them, or keep it
with no-pull-up flag, then no pull-up flag in the dts for default..

static void sdhci_phy_1_8v_init_no_pull(struct sdhci_host *host)
{
uint32_t val;
sdhci_writel(host, 1, DWC_MSHC_PTR_PHY_R);
sdhci_writeb(host, 1 << 4, PHY_SDCLKDL_CNFG_R);
sdhci_writeb(host, 0x40, PHY_SDCLKDL_DC_R);

val = sdhci_readb(host, PHY_SDCLKDL_CNFG_R);
val &= ~(1 << 4);
sdhci_writeb(host, val, PHY_SDCLKDL_CNFG_R);

val = sdhci_readw(host, PHY_CMDPAD_CNFG_R);
sdhci_writew(host, val | 1, PHY_CMDPAD_CNFG_R);

val = sdhci_readw(host, PHY_DATAPAD_CNFG_R);
sdhci_writew(host, val | 1, PHY_DATAPAD_CNFG_R);

val = sdhci_readw(host, PHY_RSTNPAD_CNFG_R);
sdhci_writew(host, val | 1, PHY_RSTNPAD_CNFG_R);

val = sdhci_readw(host, PHY_STBPAD_CNFG_R);
sdhci_writew(host, val | 1, PHY_STBPAD_CNFG_R);

val = sdhci_readb(host, PHY_DLL_CTRL_R);
sdhci_writeb(host, val | 1, PHY_DLL_CTRL_R);
}

static void sdhci_phy_3_3v_init_no_pull(struct sdhci_host *host)
{
uint32_t val;
sdhci_writel(host, 1, DWC_MSHC_PTR_PHY_R);
sdhci_writeb(host, 1 << 4, PHY_SDCLKDL_CNFG_R);
sdhci_writeb(host, 0x40, PHY_SDCLKDL_DC_R);

val = sdhci_readb(host, PHY_SDCLKDL_CNFG_R);
val &= ~(1 << 4);
sdhci_writeb(host, val, PHY_SDCLKDL_CNFG_R);

val = sdhci_readw(host, PHY_CMDPAD_CNFG_R);
sdhci_writew(host, val | 2, PHY_CMDPAD_CNFG_R);

val = sdhci_readw(host, PHY_DATAPAD_CNFG_R);
sdhci_writew(host, val | 2, PHY_DATAPAD_CNFG_R);

val = sdhci_readw(host, PHY_RSTNPAD_CNFG_R);
sdhci_writew(host, val | 2, PHY_RSTNPAD_CNFG_R);

val = sdhci_readw(host, PHY_STBPAD_CNFG_R);
sdhci_writew(host, val | 2, PHY_STBPAD_CNFG_R);

val = sdhci_readb(host, PHY_DLL_CTRL_R);
sdhci_writeb(host, val | 1, PHY_DLL_CTRL_R);
}

>
> Thanks,
> Drew
>
> [1] https://git.beagleboard.org/beaglev-ahead/BeagleBoard-DeviceTrees/-/blob/v5.10.x-ti-unified/src/riscv/light-beagle-ref.dts
> [2] https://github.com/revyos/thead-kernel/blob/lpi4a/arch/riscv/boot/dts/thead/light-lpi4a-ref.dts

--
Best Regards
Guo Ren