RE: [PATCH v2 01/11] dt-bindings: mmc: arasan: Update documentation for SD Card Clock

[Manish Narani <MNARANI@xilinx.com>]

Hi Heiko/Uffe,



> -----Original Message-----
> From: Heiko Stuebner <heiko@sntech.de>
> Sent: Thursday, August 22, 2019 11:53 PM
> To: Ulf Hansson <ulf.hansson@linaro.org>; linux-mmc@vger.kernel.org
> Cc: Manish Narani <MNARANI@xilinx.com>; Rob Herring <robh@kernel.org>;
> mark.rutland@arm.com; Michal Simek <michals@xilinx.com>;
> adrian.hunter@intel.com; christoph.muellner@theobroma-systems.com;
> philipp.tomsich@theobroma-systems.com; viresh.kumar@linaro.org;
> scott.branden@broadcom.com; ayaka@soulik.info; kernel@esmil.dk;
> tony.xie@rock-chips.com; Rajan Vaja <RAJANV@xilinx.com>;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; linux-rockchip@lists.infradead.org
> Subject: Re: [PATCH v2 01/11] dt-bindings: mmc: arasan: Update
> documentation for SD Card Clock
> 
> Am Donnerstag, 22. August 2019, 15:38:26 CEST schrieb Ulf Hansson:
> > [...]
> >
> > > > > > > ---
> > > > > > >  Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 15
> > > > ++++++++++-
> > > > > > ----
> > > > > > >  1 file changed, 10 insertions(+), 5 deletions(-)
> > > > > > >
> > > > > > > diff --git
> a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> > > > > > b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> > > > > > > index 1edbb04..15c6397 100644
> > > > > > > --- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> > > > > > > +++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> > > > > > > @@ -23,6 +23,10 @@ Required Properties:
> > > > > > >    - reg: From mmc bindings: Register location and length.
> > > > > > >    - clocks: From clock bindings: Handles to clock inputs.
> > > > > > >    - clock-names: From clock bindings: Tuple including "clk_xin" and
> > > > "clk_ahb"
> > > > > > > +            Apart from these two there is one more optional clock
> which
> > > > > > > +            is "clk_sdcard". This clock represents output clock from
> > > > > > > +            controller and card. This must be specified when #clock-
> cells
> > > > > > > +            is specified.
> > > > > > >    - interrupts: Interrupt specifier
> > > > > > >
> > > > > > >  Required Properties for "arasan,sdhci-5.1":
> > > > > > > @@ -36,9 +40,10 @@ Optional Properties:
> > > > > > >    - clock-output-names: If specified, this will be the name of the card
> > > > clock
> > > > > > >      which will be exposed by this device.  Required if #clock-cells is
> > > > > > >      specified.
> > > > > > > -  - #clock-cells: If specified this should be the value <0>.  With this
> > > > property
> > > > > > > -    in place we will export a clock representing the Card Clock.  This
> clock
> > > > > > > -    is expected to be consumed by our PHY.  You must also specify
> > > > > > > +  - #clock-cells: If specified this should be the value <0>. With this
> > > > > > > +    property in place we will export one clock representing the Card
> > > > > > > +    Clock. This clock is expected to be consumed by our PHY. You
> must
> > > > also
> > > > > > > +    specify
> > > > > >
> > > > > > specify what?
> > > > > I think this line was already there, I missed to correct it, Will update in
> v3.
> > > > >
> > > > > >
> > > > > > The 3rd clock input I assume? This statement means any existing users
> > > > > > with 2 clock inputs and #clock-cells are in error now. Is that correct?
> > > > > Yes, this is correct. So far there was only one vendor using '#clock-cells'
> > > > which is Rockchip. I have sent DT patch (02/11) for that also.
> > > > > Here this is needed as earlier implementation isn't correct as suggested
> by
> > > > Uffe. (https://lkml.org/lkml/2019/6/20/486) .
> > > >
> > > > I am not sure how big of a problem the backwards compatible thingy
> > > > with DT is, in general we must not break it. What do you say Manish?
> > >
> > > Though I agree with Uffe on this, there is no other way from my
> understanding. Please suggest.
> > >
> > > >
> > > > As a workaround, would it be possible to use
> > > > of_clk_get_from_provider() somehow to address the compatibility issue?
> > >
> > > For this to be used we have to parse 'clkspec' from the DT node and pass
> the same as an argument to this function. In this case also the DT node needs to
> be updated, which is same as we have done in this series.
> >
> > Alright. I guess breaking DTBs for Rockchip platforms isn't
> > acceptable, especially if those are already widely deployed, which I
> > have no idea of....
> 
> The arasan sdhci is part of the rk3399, so every SBC using that SoC, but
> also the whole Gru series of ChromeOS devices (Samsung Chromebook Plus
> among them) would be affected.

Thanks for confirming. This will be taken care of. I will go back to v1 changes and will send v3.

Thanks,
Manish