linux-kernel - Re: [PATCH 3/3] usb: renesas_usbhs: Reorder clock handling and power management in probe

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Message-ID: <CA+V-a8vqnNN119RbRJ5FvEUkWOd+FEHr9g+B3YnZasn=y7MWaQ@mail.gmail.com>
Date: Mon, 31 Mar 2025 11:57:03 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, linux-usb@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Biju Das <biju.das.jz@...renesas.com>, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 3/3] usb: renesas_usbhs: Reorder clock handling and power
 management in probe

Hi Morimoto san,

On Mon, Mar 31, 2025 at 1:05 AM Kuninori Morimoto
<kuninori.morimoto.gx@...esas.com> wrote:
>
>
> Hi Lad, Prabhakar
>
> > > >     usbhs_probe()
> > > >         usbhs_sys_clock_ctrl()
> > > >             usbhs_bset()
> > > >                 usbhs_write()
> > > >                     iowrite16()  <-- Register access before enabling clocks
> > >
> > > This patch itself is not so bad idea, but basically, we should not assume
> > > the power/clock was enabled since kernel boot.
> > > In this driver, register access happen only during power enable <->  power
> > > disable (except your issue case), and this is good idea. So, the strange
> > > is usbhs_sys_clock_ctrl() call in usbhs_probe() (without power enable) I
> > > guess.
> > >
> > > According to the comment, it is just caring boot loader, and
> > > usbhs_sys_clock_ctrl() itself will be called when usbhsc_power_ctrl() was
> > > called anyway. And more, if my understanding was correct, Renesas clock
> > > driver will stop all unused devices clock/power after boot.
> > > So maybe we can just remove strange usbhs_sys_clock_ctrl() from usbhs_probe() ?
> > >
> >
> > After dropping usbhs_sys_clock_ctrl and removing the clock enabling
> > done in this patch and with  `CONFIG_USB_G_SERIAL=y` I hit the same
> > issue.
>
> Ah...
> OK, not only usbhs_sys_clock_ctrl(), but other initializer also
> missing power in probe(). Thank you for reporting, your original patch
> is reasonable.
>
Thanks! I'll send a V2 incorporating your review comments next week
after v6.15-rc1 is released.

Cheers,
Prabhakar