linux-kernel - Re: [PATCH v4 7/7] phy: exynos5-usbdrd: allow DWC3 runtime suspend with UDC bound (E850+)

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Message-ID: <Z22TljXrbBNazNwW@google.com>
Date: Thu, 26 Dec 2024 09:34:14 -0800
From: William McVicker <willmcvicker@...gle.com>
To: André Draszik <andre.draszik@...aro.org>
Cc: Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Peter Griffin <peter.griffin@...aro.org>,
	Tudor Ambarus <tudor.ambarus@...aro.org>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	Roy Luo <royluo@...gle.com>, kernel-team@...roid.com,
	linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v4 7/7] phy: exynos5-usbdrd: allow DWC3 runtime suspend
 with UDC bound (E850+)

On 12/06/2024, André Draszik wrote:
> To make USB runtime suspend work when a UDC has been bound, the phy
> needs to inform the USBDRD controller (DWC3) that Vbus and bvalid are
> gone, so that it can in turn raise the respective gadget interrupt with
> event == DWC3_DEVICE_EVENT_DISCONNECT, which will cause the USB stack
> to clean up, allowing DWC3 to enter runtime suspend.
> 
> On e850 and gs101 this isn't working, as the respective signals are not
> directly connected, and instead this driver uses override bits in the
> PHY IP to set those signals. It currently forcefully sets them to 'on',
> so the above mentioned interrupt will not be raised, preventing runtime
> suspend.
> 
> To detect that state, update this driver to act on the TCPC's
> orientation signal - when orientation == NONE, Vbus is gone and we can
> clear the respective bits. Similarly, for other orientation values we
> re-enable them.
> 
> This makes runtime suspend work on platforms with a TCPC (like Pixel6),
> while keeping compatibility with platforms without (e850-96).
> 
> With runtime suspend working, USB-C cable orientation detection now
> also fully works on such platforms, and the link comes up as Superspeed
> as expected irrespective of the cable orientation and whether UDC /
> gadget are configured and active.
> 
> Signed-off-by: André Draszik <andre.draszik@...aro.org>

Verified on my Pixel 6 Pro.

Tested-by: Will McVicker <willmcvicker@...gle.com>

Thanks,
Will

<snip>