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 09:30:41 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>, "Lad, Prabhakar"
	<prabhakar.csengg@...il.com>
CC: "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 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/platform.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?

See [1] and [2]

[1]
https://lore.kernel.org/linux-renesas-soc/20240616105402.45211-1-biju.das.jz@bp.renesas.com/

[2]
https://elixir.bootlin.com/linux/latest/source/drivers/regulator/vqmmc-ipq4019-regulator.c

Cheers,
Biju