RE: [PATCH v2] arm64: dts: renesas: add sdhi/mmc aliases

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Magnus Damm <magnus.damm@gmail.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>
Subject: RE: [PATCH v2] arm64: dts: renesas: add sdhi/mmc aliases
Date: Tue, 9 Feb 2021 05:02:33 +0000	[thread overview]
Message-ID: <TY2PR01MB369215A1E5832585BB15B306D88E9@TY2PR01MB3692.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdVgTfp5-q08VvUEEtLOE+LeeEPCY5wsfvhCyuHGa9Xung@mail.gmail.com>

Hi Geert-san,

> From: Geert Uytterhoeven, Sent: Monday, February 8, 2021 10:01 PM
> On Mon, Feb 8, 2021 at 1:31 PM Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@renesas.com> wrote:
> > > From: Geert Uytterhoeven, Sent: Monday, February 8, 2021 8:45 PM
> > > On Mon, Feb 8, 2021 at 11:53 AM Yoshihiro Shimoda
> > > <yoshihiro.shimoda.uh@renesas.com> wrote:
> > > > > From: Geert Uytterhoeven, Sent: Monday, February 8, 2021 6:46 PM
> > > > > On Mon, Feb 8, 2021 at 3:48 AM Yoshihiro Shimoda
> > > > > <yoshihiro.shimoda.uh@renesas.com> wrote:
> > > > > > --- a/arch/arm64/boot/dts/renesas/r8a774c0.dtsi
> > > > > > +++ b/arch/arm64/boot/dts/renesas/r8a774c0.dtsi
> > > > > > @@ -14,6 +14,12 @@
> > > > > >         #address-cells = <2>;
> > > > > >         #size-cells = <2>;
> > > > > >
> > > > > > +       aliases {
> > > > > > +               mmc0 = &sdhi0;
> > > > > > +               mmc1 = &sdhi1;
> > > > > > +               mmc3 = &sdhi3;
> > > > > > +       };
> > > > >
> > > > > BTW, this is one of the other issues with aliases: where is mmc2?
> > > > > Yes, I know why it's done this way ;-)
> > > >
> > > > Ah, I intended to assign the aliases 1:1 between "mmcN" and "sdhiN".
> > > > But, should we use "mmc2 = &sdhi3;" instead on r8a774c0 and r8a77990?
> > >
> > > I'm fine with the numbering you used, as the aliases match the existing
> > > labels.
> > >
> > > However, on R-Car Gen2 we did use contiguous numbering of the labels,
> > > as early revisions of the datasheet used contiguous numbering for the
> > > interfaces, while later revisions changed this.
> > > I think the sensible thing to do is to make the aliases match the existing
> > > labels, too.
> >
> > Thank you for the comment about R-Car Gen2. I didn't realized that.
> > On R-Car Gen2 SoCs, they also have mmcif controllers. So, I'm thinking
> > the mmc aliases should use contiguous numbering for Gen2 mmcif and sdhi
> > at least. And, perhaps, I feel using same this rule (contiguous numbering) on
> > Gen3 is better. But, what do you think?
> 
> Thank you for the comment about MMCIF,  I had forgotten about that.
> R-Car Gen2 is even more complicated, as you have 1, 3, or 4 SDHI
> instances, and may have 1 or 2 MMC instances.  So is mmc0 the first
> SDHI interface, or the first MMC interface?

I intended that mmc0 is the first MMC interface as alphabet ordering
of the labels (mmcifN vs sdhiN).

> Worse, they share pins. So the user can actually choose to use an SDHI or
> MMCIF instance on some of the pin groups (for now ignoring that MMCIF
> supports 1/4/8 bit, and SDHI only 1/4).
> 
> Hence I think on R-Car Gen2 you have to add the aliases to the board DTS
> files, based on the connector labels on the physical boards, which
> brings us back to the original idea behind the aliases...

I got it. I'll add such aliases on R-Car Gen2.

Best regards,
Yoshihiro Shimoda