Re: [PATCH 3/3] usb: dwc2: prevent core phy initialisation - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Cc: Quentin Schulz <foss+kernel@0leil.net>,
	Minas Harutyunyan <hminas@synopsys.com>,
	linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
	William Wu <william.wu@rock-chips.com>,
	Bin Yang <yangbin@rock-chips.com>,
	Frank Wang <frank.wang@rock-chips.com>
Subject: Re: [PATCH 3/3] usb: dwc2: prevent core phy initialisation
Date: Fri, 9 Dec 2022 13:13:56 +0100	[thread overview]
Message-ID: <Y5MmhEMMx2sy91LS@kroah.com> (raw)
In-Reply-To: <69c0f9c0-5c89-e99e-c807-9963ca377093@theobroma-systems.com>

On Fri, Dec 09, 2022 at 12:15:34PM +0100, Quentin Schulz wrote:
> Hi Greg,
> 
> On 12/8/22 16:53, Greg Kroah-Hartman wrote:
> > On Wed, Dec 07, 2022 at 02:19:18PM +0100, Quentin Schulz wrote:
> > > From: Bin Yang <yangbin@rock-chips.com>
> > > 
> > > The usb phys need to be controlled dynamically on some Rockchip SoCs.
> > > So set the new HCD flag which prevents USB core from trying to manage
> > > our phys.
> > > 
> > > Signed-off-by: Bin Yang <yangbin@rock-chips.com>
> > > Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
> > > Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
> > > ---
> > >   drivers/usb/dwc2/hcd.c | 7 +++++++
> > >   1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> > > index 657f1f659ffaf..757a66fa32fa8 100644
> > > --- a/drivers/usb/dwc2/hcd.c
> > > +++ b/drivers/usb/dwc2/hcd.c
> > > @@ -5315,6 +5315,13 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg)
> > >   	if (!IS_ERR_OR_NULL(hsotg->uphy))
> > >   		otg_set_host(hsotg->uphy->otg, &hcd->self);
> > > +	/*
> > > +	 * do not manage the PHY state in the HCD core, instead let the driver
> > > +	 * handle this (for example if the PHY can only be turned on after a
> > > +	 * specific event)
> > > +	 */
> > > +	hcd->skip_phy_initialization = 1;
> > 
> > Wait, doesn't this mess with the phy logic for all other chips that use
> > this IP block?  Have you tested this on other systems?
> > 
> 
> I have not. I asked this in the cover-letter but I guess I should have made
> the patch series an RFC for this reason?

Ah, should I drop the first 2 in this series that I already applied?

> > I'd like some verification first before taking this change as it seems
> > very specific-platform.
> > 
> 
> There's already some platform-specific callbacks for the driver (see
> dwc2_set_rk_params in drivers/usb/dwc2/params.c) but this gets called too
> early, before hcd structure is actually allocated. So we either need to use
> some "proxy"/shadow variable in dwc2_core_params and then update it right
> after hcd gets allocated or have another platform-specific callback only for
> hcd (post-)initialization.
> 
> Nothing too fancy so shouldn't take too long to implement. Any preference?
> Something else?

Which ever you think would be simplest.

thanks,

greg k-h