linux-kernel - Re: [PATCH] Revert "usb: cdns3: core: quit if it uses role switch class"

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Message-ID: <20201124110020.GA1008337@kuha.fi.intel.com>
Date:   Tue, 24 Nov 2020 13:00:20 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Roger Quadros <rogerq@...com>
Cc:     Peter Chen <peter.chen@....com>,
        "pawell@...ence.com" <pawell@...ence.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "usb: cdns3: core: quit if it uses role switch
 class"

On Tue, Nov 24, 2020 at 12:33:34PM +0200, Roger Quadros wrote:
> +Heikki
> 
> Peter,
> 
> On 24/11/2020 11:57, Peter Chen wrote:
> > 
> > 
> > 
> > Best regards,
> > Peter Chen
> > 
> > > -----Original Message-----
> > > From: Roger Quadros <rogerq@...com>
> > > Sent: 2020年11月24日 17:39
> > > To: Peter Chen <peter.chen@....com>
> > > Cc: pawell@...ence.com; gregkh@...uxfoundation.org; balbi@...nel.org;
> > > linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH] Revert "usb: cdns3: core: quit if it uses role switch class"
> > > 
> > > Peter,
> > > 
> > > On 24/11/2020 08:43, Peter Chen wrote:
> > > > On 20-11-23 13:50:51, Roger Quadros wrote:
> > > > > This reverts commit 50642709f6590fe40afa6d22c32f23f5b842aed5.
> > > > > 
> > > > > This commit breaks hardware based role switching on TI platforms.
> > > > > cdns->role_sw is always going to be non-zero as it is a pointer
> > > > > to the usb_role_switch instance. Some other means needs to be used if
> > > > > hardware based role switching is not required by the platform.
> > > > > 
> > > > > Signed-off-by: Roger Quadros <rogerq@...com>
> > > > > ---
> > > > >    drivers/usb/cdns3/core.c | 4 ----
> > > > >    1 file changed, 4 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> > > > > index a0f73d4711ae..4c1445cf2ad0 100644
> > > > > --- a/drivers/usb/cdns3/core.c
> > > > > +++ b/drivers/usb/cdns3/core.c
> > > > > @@ -280,10 +280,6 @@ int cdns3_hw_role_switch(struct cdns3 *cdns)
> > > > >    	enum usb_role real_role, current_role;
> > > > >    	int ret = 0;
> > > > > 
> > > > > -	/* Depends on role switch class */
> > > > > -	if (cdns->role_sw)
> > > > > -		return 0;
> > > > > -
> > > > >    	pm_runtime_get_sync(cdns->dev);
> > > > > 
> > > > >    	current_role = cdns->role;
> > > > > --
> > > > 
> > > > Hi Roger,
> > > > 
> > > > I am sorry about that. Do you use role switch /sys entry, if you have
> > > > used, I prefer using "usb-role-switch" property at dts to judge if SoC
> > > > OTG signals or external signals for role switch. If you have not used
> > > > it, I prefer only setting cdns->role_sw for role switch use cases.
> > > > 
> > > 
> > > We use both hardware role switch and /sys entries for manually forcing a
> > > certain role.
> > > 
> > > We do not set any "usb-role-switch" property at DTS.
> > > 
> > > Currently cdns->role_sw is being always set by driver irrespective of any DT
> > > property, so this patch is clearly wrong and needs to be reverted.
> > > 
> > > What do you think?
> > > 
> > 
> > Could you accept below fix?
> > 
> > diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> > index 2e469139769f..fdd52e87a7b2 100644
> > --- a/drivers/usb/cdns3/core.c
> > +++ b/drivers/usb/cdns3/core.c
> > @@ -280,8 +280,8 @@ int cdns3_hw_role_switch(struct cdns3 *cdns)
> >          enum usb_role real_role, current_role;
> >          int ret = 0;
> > 
> > -       /* Depends on role switch class */
> > -       if (cdns->role_sw)
> > +       /* quit if switch role through external signals */
> > +       if (device_property_read_bool(cdns->dev, "usb-role-switch"))
> >                  return 0;
> > 
> >          pm_runtime_get_sync(cdns->dev);
> 
> Although this will fix the issue I don't think this is making the driver to behave
> as expected with usb-role-switch property.
> 
> Now, even if usb-role-switch property is not present the driver will still register
> the role switch driver.
> 
> I think we need to register the role switch driver only if usb-role-switch property
> is present. We would also need to set the default role if role-switch-default-mode is present.
> 
> How about the following? It still doesn't handle role-switch-default-mode property though.
> 
> 
> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> index 4c1445cf2ad0..986b56a9940c 100644
> --- a/drivers/usb/cdns3/core.c
> +++ b/drivers/usb/cdns3/core.c
> @@ -532,11 +532,13 @@ static int cdns3_probe(struct platform_device *pdev)
>  	if (device_property_read_bool(dev, "usb-role-switch"))
>  		sw_desc.fwnode = dev->fwnode;
> -	cdns->role_sw = usb_role_switch_register(dev, &sw_desc);
> -	if (IS_ERR(cdns->role_sw)) {
> -		ret = PTR_ERR(cdns->role_sw);
> -		dev_warn(dev, "Unable to register Role Switch\n");
> -		goto err3;
> +	if (device_property_read_bool(cdns->dev, "usb-role-switch")) {
> +		cdns->role_sw = usb_role_switch_register(dev, &sw_desc);
> +		if (IS_ERR(cdns->role_sw)) {
> +			ret = PTR_ERR(cdns->role_sw);
> +			dev_warn(dev, "Unable to register Role Switch\n");
> +			goto err3;
> +		}
>  	}
>  	if (cdns->wakeup_irq) {

Makes sense to me. FWIW:

Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

thanks,

-- 
heikki