Re: [PATCH v9 3/4] clk: meson: add DT documentation for emmc clock controller

[Liang Yang]

Hi Martin,

On 2022/1/15 8:09, Martin Blumenstingl wrote:
> [ EXTERNAL EMAIL ]
>
> Hi Liang,
>
> On Fri, Jan 14, 2022 at 4:06 AM Liang Yang <liang.yang@xxxxxxxxxxx> wrote:
> [...]
> > > > +properties:
> > > > +  compatible:
> > > > +    enum:
> > > > +      - "amlogic,axg-mmc-clkc", "syscon"
> > >
> > > Why is it a syscon?
> >
> > The register documented by reg is shared with SD/eMMC controller port C,
> > and it need to be ops on NFC driver.
> Can you please share an example how the .dts would look like in the
> end for two example cases:
> 1) using the sd_emmc_c MMC interface > 2) not using the MMC interface of sd_emmc_c but only using it's clocks
> for the NFC
I think both EMMC(although it is not implemented by 'axg-mmc-clkc'  yet) 
and NAND clock have the same way in dts:
		......
		clocks = <&clkc CLKID_SD_EMMC_C>,
			<&sd_emmc_c_clkc CLKID_MMC_DIV>,
			<&sd_emmc_c_clkc CLKID_MMC_PHASE_RX>,
			<&sd_emmc_c_clkc CLKID_MMC_PHASE_TX>;
		clock-names = "core", "device", "rx", "tx";
		amlogic,mmc-syscon = <&sd_emmc_c_clkc>;
		......

> Initially I wanted to suggest the usage of a sub-node with compatible
> = "mmc-slot" (see
> Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt for an
> example) to decide whether the MMC controller is registered or whether
> just the clock controller is registered.
> However, the mmc-slot compatible string is not documented in
> Documentation/devicetree/bindings/mmc/mmc-controller.yaml currently.
> Maybe the MMC maintainers have any suggestions if other IPs have
> similar requirements (for IPs with shared parts).
>
>
> Best regards,
> Martin
>
> .