[v4] usb: dwc2: dwc2_vbus_supply_init: fix error check

[Heiko Stuebner <heiko@sntech.de>]

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@st.com>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.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.

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@sntech.de>


> v2: Only overwrite the error in the pointer after checking it (Heiko
>     Stübner <heiko@sntech.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@intel.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);
>  }
>  
>  /*
>
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