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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <01fc3101ab2e3898932afeaaaf060a6676cdf323.camel@pengutronix.de>
Date: Tue, 07 Oct 2025 11:44:06 +0200
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Biju Das <biju.das.jz@...renesas.com>, 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 Biju,

On Di, 2025-10-07 at 04:02 +0000, Biju Das wrote:
> 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

I still can't look at this, right? The USB2PHY control register space
appears to be documented in the "RZ/V2H Group User's Manual: Hardware
(Additional document)" (under NDA).

> > 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.

So this is a mux for the VBUS_SEL signal?

Why don't the USB host controller drivers parse their "dr_mode"
property themselves and control USB2PHY VBENCTRL via the mux API, for
example?

regards
Philipp