linux-kernel - RE: [PATCH 04/18] reset: rzv2h-usb2phy: Set VBENCTL register for OTG mode

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Message-ID:
 <TY3PR01MB1134635745721CC005B35702286E0A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Tue, 7 Oct 2025 04:02:54 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Philipp Zabel <p.zabel@...gutronix.de>, Tommaso Merciai
	<tommaso.merciai.xr@...renesas.com>, Tommaso Merciai <tomm.merciai@...il.com>
CC: "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, Vinod Koul
	<vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, Geert
 Uytterhoeven <geert+renesas@...der.be>, magnus.damm <magnus.damm@...il.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>, "linux-phy@...ts.infradead.org"
	<linux-phy@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 04/18] reset: rzv2h-usb2phy: Set VBENCTL register for OTG
 mode

Hi Philipp,

Thanks for the feedback.

> -----Original Message-----
> From: Philipp Zabel <p.zabel@...gutronix.de>
> Sent: 06 October 2025 17:32
> Subject: Re: [PATCH 04/18] reset: rzv2h-usb2phy: Set VBENCTL register for OTG mode
> 
> On Mi, 2025-10-01 at 23:26 +0200, Tommaso Merciai wrote:
> > Add logic to set the VBENCTL register when the USB controller operates
> > in OTG mode. This is required to ensure proper USB transceiver
> > behavior when the device is configured as OTG.
> >
> > Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>
> 
> I had reservations about this driver before, because of the opaque register initialization sequence, and
> I was told that no, this is a reset driver alright [1].

The latest hardware manual document about VBENCTRL register which sets source for VBUS selection.
s
> 
> Can you please try to find a proper abstraction for this, because drivers/reset is not the correct place
> for USB OTG mode handling.

Sorry for the confusion. This driver is not handling USB OTG mode. It just configures VBENCTRL(one time setting)
that selects the source for VBUS_SEL. Actual USB OTG mode handling is done USB PHY driver
which sets host/device mode based on ID detection.

Cheers,
Biju