Re: [PATCH 1/2] usb: dwc2: optionally assert phy "full reset" when waking up

From: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Randy Li <randy.li-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	johnyoun-HKixBCOQz3hWk0Htik3J/w@public.gmane.org,
	gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org,
	mark.rutland-5wv7dgnIgG8@public.gmane.org,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	ayaka-xPW3/0Ywev/iB9QmIjCX8w@public.gmane.org,
	eddie.cai-TNX95d0MmH7DzftRWevZcw@public.gmane.org
Subject: Re: [PATCH 1/2] usb: dwc2: optionally assert phy "full reset" when waking up
Date: Tue, 19 Jul 2016 20:36:14 -0500	[thread overview]
Message-ID: <20160720013614.GA12210@rob-hp-laptop> (raw)
In-Reply-To: <1468929933-6971-1-git-send-email-randy.li-TNX95d0MmH7DzftRWevZcw@public.gmane.org>

On Tue, Jul 19, 2016 at 08:05:33PM +0800, Randy Li wrote:
> From: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> 
> On the rk3288 USB host-only port (the one that's not the OTG-enabled
> port) the PHY can get into a bad state when a wakeup is asserted (not
> just a wakeup from full system suspend but also a wakeup from
> autosuspend). The problem is caused by a design fault in IC, Rockchip
> have confirmed it and fix this problem in the future IC model.
> 
> We can get the PHY out of its bad state by asserting its "port reset",
> but unfortunately that seems to assert a reset onto the USB bus so it
> could confuse things if we don't actually deenumerate / reenumerate the
> device.
> 
> We can also get the PHY out of its bad state by fully resetting it using
> the reset from the CRU (clock reset unit), which does a more full
> reset.  The CRU-based reset appears to actually cause devices on the bus
> to be removed and reinserted, which fixes the problem (albeit in a hacky
> way).
> 
> It's unfortunate that we need to do a full re-enumeration of devices at
> wakeup time, but this is better than alternative of letting the bus get
> wedged.
> 
> Signed-off-by: Douglas Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Signed-off-by: Yunzhi Li <lyz-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> Reviewed-by: Randy Li <randy.li-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/usb/dwc2.txt |  7 +++++++
>  drivers/usb/dwc2/core.h                        |  5 +++++
>  drivers/usb/dwc2/core_intr.c                   | 14 ++++++++++++++
>  drivers/usb/dwc2/platform.c                    | 13 +++++++++++++
>  4 files changed, 39 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/dwc2.txt b/Documentation/devicetree/bindings/usb/dwc2.txt
> index 20a68bf..40c63ae 100644
> --- a/Documentation/devicetree/bindings/usb/dwc2.txt
> +++ b/Documentation/devicetree/bindings/usb/dwc2.txt
> @@ -20,6 +20,13 @@ Refer to clk/clock-bindings.txt for generic clock consumer properties
>  Optional properties:
>  - phys: phy provider specifier
>  - phy-names: shall be "usb2-phy"
> +- snps,need-phy-full-reset-on-wake: if present indicates that we need to reset

Bikeshedding, but 'snps,full-phy-reset-on-wake' is slightly shorter.

However, this isn't really even needed. It should be implied by the SoC 
specific compatible string.

> +  the PHY when we detect a wakeup due to a hardware errata.  If present you
> +  must specify a "phy-full-reset" reset.
> +
> +Resets:
> +- phy-full-reset (optional): Fully resets the PHY (Only used by rk3288 Soc).

This property belows in the phy node as that is where the reset is 
attached to and why is it not using the standard binding "resets"?

Rob
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