linux-kernel - RE: [RFC PATCH v2 3/3] mmc: renesas_sdhi: Add support for RZ/V2H(P) SoC

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Date: Thu, 20 Jun 2024 09:49:42 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
CC: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>, Fabrizio Castro
	<fabrizio.castro.jz@...esas.com>, Conor Dooley <conor+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, Ulf Hansson
	<ulf.hansson@...aro.org>, Magnus Damm <magnus.damm@...il.com>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Geert
 Uytterhoeven <geert+renesas@...der.be>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v2 3/3] mmc: renesas_sdhi: Add support for RZ/V2H(P)
 SoC

Hi Prabhakar,

> -----Original Message-----
> From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> Subject: Re: [RFC PATCH v2 3/3] mmc: renesas_sdhi: Add support for RZ/V2H(P) SoC
> 
> Hi Biju,
> 
> On Thu, Jun 20, 2024 at 10:30 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> >
> > Hi Wolfram, Prabhakar,
> >
> > > -----Original Message-----
> > > From: Wolfram Sang <wsa+renesas@...g-engineering.com>
> > > Sent: Thursday, June 20, 2024 8:40 AM
> > > Subject: Re: [RFC PATCH v2 3/3] mmc: renesas_sdhi: Add support for
> > > RZ/V2H(P) SoC
> > >
> > > Hi Prabhakar,
> > >
> > > > I did give it a try with platform_driver_probe() and failed.
> > >
> > > Ok, thanks for trying nonetheless!
> > >
> > > > - Firstly I had to move the regulator node outside the SDHI node
> > > > for
> > > > platform_driver_probe() to succeed or else it failed with -ENODEV
> > > > (at
> > > > https://elixir.bootlin.com/linux/latest/source/drivers/base/platfo
> > > > rm.c
> > > > #L953)
> > >
> > > This makes sense to me because it is just a "regular" regulator.
> > >
> > > > - In Renesas SoCs we have multiple instances of SDHI, the problem
> > > > being for each instance we are calling platform_driver_probe().
> > > > Which causes a problem as the regulator node will use the first device.
> > >
> > > I see... we would need a reg property to differentiate between the
> > > internal regulators but that is already used by the parent SDHI node.
> > >
> > > Okay, so let's scrap that idea. However, we need to ensure that we
> > > can still have an external regulator. Seeing the bindings, it looks
> > > like you enable the internal regulator with the "vqmmc- r9a09g057-regulator"
> > > property? I wonder now if we can simplify this to an
> > > "use-internal-regulator" property because we have 'compatible' already to differentiate? Needs
> advice from DT maintainers, probably.
> >
> > Why this cannot be modelled as a regular "regulator" as a child device of SDHI device?
> >
> The current implementation does implement the regulator as a child device of the sdhi node [0]
> itself.
> 
> Wolfram was suggesting to have the regulator outside and use platform_driver_probe(), which caused
> an issue as mentioned above.

You, mean standalone node with a device compatible for each SDHI device nodes(Assuming 3 sdhi devices)?

3 SDHI devices nodes(stand alone) + 3 regulator device nodes (stand alone) ?

Or

3 SDHI devices nodes(stand alone) + 1 regulator device node(stand alone)


Cheers,
Biju