Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card

[Doug Anderson]

Hi,

On Wed, Mar 24, 2021 at 8:59 PM Veerabhadrarao Badiganti
<vbadigan@xxxxxxxxxxxxxx> wrote:
>
> >> +                       clocks = <&gcc GCC_SDCC1_APPS_CLK>,
> >> +                                       <&gcc GCC_SDCC1_AHB_CLK>,
> >> +                                       <&rpmhcc RPMH_CXO_CLK>;
> >> +                       clock-names = "core", "iface", "xo";
> > I'm curious: why is the "xo" clock needed here but not for sc7180?
> Actually its needed even for sc7180. We are making use of this clock in
> msm_init_cm_dll()
> The default PoR value is also same as calculated value for
> HS200/HS400/SDR104 modes.
> But just not to rely on default register values we need this entry.

Can you post a patch for sc7180?


> >> +                       bus-width = <4>;
> >> +
> >> +                       no-mmc;
> >> +                       no-sdio;
> > Similar question to above: why exactly would mmc not work? Are you
> > saying that if someone hooked this up to a full sized SD card slot and
> > placed an MMC card into the slot that it wouldn't work? Similar
> > question about SDIO. If someone placed an external SDIO card into your
> > slot, would it not work?
> >
> As mentioned above, its just to optimize SDcard scan time a little.

OK. ...but while the eMMC one can make sense since the eMMC is
soldered down (but in the board dts file, not in the SoC dtsi file) I
think you should just remove these for SD card because:

1. Even if only a uSD slot is exposed it's still _possible_ for
someone to insert a card that uses MMC or SDIO signaling. If nothing
else I have a (probably non-compliant) adapter that plugs into a uSD
slot and provides a full sided SD slot. I could plug an MMC card or
SDIO card in.

2. Presumably the SD card scan time optimization is tiny.


-Doug