linux-kernel - Re: [PATCH v5 07/12] usb: cdns3-ti: add J7200 support with reset-on-resume behavior

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Message-Id: <D42NNVGT7JLU.2CFGBTBNAP0E7@bootlin.com>
Date: Tue, 10 Sep 2024 15:57:40 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Roger Quadros" <rogerq@...nel.org>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Rob Herring" <robh@...nel.org>, "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Peter Chen" <peter.chen@...nel.org>, "Pawel Laszczak"
 <pawell@...ence.com>, "Mathias Nyman" <mathias.nyman@...el.com>, "Nishanth
 Menon" <nm@...com>, "Vignesh Raghavendra" <vigneshr@...com>, "Tero Kristo"
 <kristo@...nel.org>
Cc: <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
 "Kevin Hilman" <khilman@...nel.org>, Grégory Clement
 <gregory.clement@...tlin.com>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v5 07/12] usb: cdns3-ti: add J7200 support with
 reset-on-resume behavior

On Mon Aug 5, 2024 at 3:54 PM CEST, Roger Quadros wrote:
> On 26/07/2024 21:17, Théo Lebrun wrote:
> > Add ti,j7200-usb compatible. Match data indicates the controller resets
> > on resume which tells that to the cdns3 core. This in turn silences a
> > xHCI warning visible in cases of unexpected resets.
> > 
> > We also inherit the errata quirk CDNS3_DRD_SUSPEND_RESIDENCY_ENABLE from
> > the default `cdns_ti_auxdata` configuration.
> > 
> > Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> > ---
> >  drivers/usb/cdns3/cdns3-ti.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c
> > index 159814dfc856..65b8b6f4c654 100644
> > --- a/drivers/usb/cdns3/cdns3-ti.c
> > +++ b/drivers/usb/cdns3/cdns3-ti.c
> > @@ -258,7 +258,21 @@ static const struct of_dev_auxdata cdns_ti_auxdata[] = {
> >  	{},
> >  };
> >  
> > +static struct cdns3_platform_data cdns_ti_j7200_pdata = {
> > +	.quirks = CDNS3_RESET_ON_RESUME |
>
> But you mentioned that the behavior can be different based on which
> idle state the system went into.
> Setting this flag will means Reset is required on every resume.

No, this flag's only behavior is to enable XHCI_RESET_ON_RESUME in the
lower xHCI stack. Code is in __cdns_host_init():

	if (cdns->pdata && (cdns->pdata->quirks & CDNS3_RESET_ON_RESUME))
		cdns->xhci_plat_data->quirks |= XHCI_RESET_ON_RESUME;

> Instead, you just need to rely on the runtime check and set the xhci->lost_power flag at resume.

I argued about my view of the XHCI_RESET_ON_RESUME quirk under
[PATCH v5 09/12].
https://lore.kernel.org/lkml/D42NIH63EHZG.KKWZR2WZB68L@bootlin.com/

Regards,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com