linux-kernel - Re: [PATCH v4] usb: dwc2: dwc2_vbus_supply

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Date:   Tue, 10 Apr 2018 17:37:46 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>
Cc:     Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Amelie Delaunay <amelie.delaunay@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v4] usb: dwc2: dwc2_vbus_supply_init: fix error check

Am Dienstag, 10. April 2018, 15:52:25 CEST schrieb Minas Harutyunyan:
> Hi Heiko,
> 
> On 4/10/2018 4:28 PM, Heiko Stuebner wrote:
> > Am Montag, 26. März 2018, 11:00:01 CEST schrieb Tomeu Vizoso:
> >> devm_regulator_get_optional returns -ENODEV if the regulator isn't
> >> there, so if that's the case we have to make sure not to leave -ENODEV
> >> in the regulator pointer.
> >> 
> >> Also, make sure we return 0 in that case, but correctly propagate any
> >> other errors. Also propagate the error from _dwc2_hcd_start.
> >> 
> >> Fixes: 531ef5ebea96 ("usb: dwc2: add support for host mode external vbus
> >> supply") Cc: Amelie Delaunay <amelie.delaunay@...com>
> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> > 
> > The patch that gets fixed here also breaks display-output on dwc2-based
> > Rockchip devices (likely even more), probably due to making the regulator
> > framework hickup.
> 
> Could you please elaborate what mean "breaks display-output".
> On which Kernel version you apply this patch?

I think I may have written that poorly. _Without_ this patch I get
display breakage on the most recent torvalds/master (merge-window)
where "usb: dwc2: add support for host mode external vbus supply" is
applied and this patch fixes the issue.

"breaks display output" means both hdmi + edp output are missing
also including the backlight staying off.

The patch we're fixing here, causes a null-pointer dereference in the
regulator framework, which seems to also cause issues when other
regulators are enabled, which I think is what I'm seeing here.


Heiko

> 
> Thanks,
> Minas
> 
> > With this patch applied, apart from not seeing the NULL-ptr, I also get
> > display output on my rk3288-veycron Chromebook again, so
> > 
> > Tested-by: Heiko Stuebner <heiko@...ech.de>
> > 
> >> v2: Only overwrite the error in the pointer after checking it (Heiko
> >> 
> >>      Stübner <heiko@...ech.de>)
> >> 
> >> v3: Remove hunks that shouldn't be in this patch
> >> v4: Don't overwrite the error code before returning it (kbuild test
> >> 
> >>      robot <lkp@...el.com>)
> >> 
> >> ---
> >> 
> >>   drivers/usb/dwc2/hcd.c | 13 ++++++++-----
> >>   1 file changed, 8 insertions(+), 5 deletions(-)
> >> 
> >> diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> >> index 190f95964000..c51b73b3e048 100644
> >> --- a/drivers/usb/dwc2/hcd.c
> >> +++ b/drivers/usb/dwc2/hcd.c
> >> @@ -358,9 +358,14 @@ static void dwc2_gusbcfg_init(struct dwc2_hsotg
> >> *hsotg)>> 
> >>   static int dwc2_vbus_supply_init(struct dwc2_hsotg *hsotg)
> >>   {
> >> 
> >> +	int ret;
> >> +
> >> 
> >>   	hsotg->vbus_supply = devm_regulator_get_optional(hsotg->dev, "vbus");
> >> 
> >> -	if (IS_ERR(hsotg->vbus_supply))
> >> -		return 0;
> >> +	if (IS_ERR(hsotg->vbus_supply)) {
> >> +		ret = PTR_ERR(hsotg->vbus_supply);
> >> +		hsotg->vbus_supply = NULL;
> >> +		return ret == -ENODEV ? 0 : ret;
> >> +	}
> >> 
> >>   	return regulator_enable(hsotg->vbus_supply);
> >>   
> >>   }
> >> 
> >> @@ -4342,9 +4347,7 @@ static int _dwc2_hcd_start(struct usb_hcd *hcd)
> >> 
> >>   	spin_unlock_irqrestore(&hsotg->lock, flags);
> >> 
> >> -	dwc2_vbus_supply_init(hsotg);
> >> -
> >> -	return 0;
> >> +	return dwc2_vbus_supply_init(hsotg);
> >> 
> >>   }
> >>   
> >>   /*