Re: [PATCH v4 2/8] usb: misc: onboard_dev: add support for non-hub devices

From: Matthias Kaehlcke <mka@chromium.org>
To: Javier Carrasco <javier.carrasco@wolfvision.net>
Cc: Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Helen Koike <helen.koike@collabora.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	linux-sound@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 2/8] usb: misc: onboard_dev: add support for non-hub devices
Date: Tue, 27 Feb 2024 17:55:07 +0000	[thread overview]
Message-ID: <Zd4h-4Nm0Kl-7mqp@google.com> (raw)
In-Reply-To: <174ce57a-3197-4251-831f-205ec5cfeae9@wolfvision.net>

On Thu, Feb 22, 2024 at 03:42:26PM +0100, Javier Carrasco wrote:
> On 21.02.24 20:24, Matthias Kaehlcke wrote:
> > On Tue, Feb 20, 2024 at 03:05:46PM +0100, Javier Carrasco wrote:
> >> Most of the functionality this driver provides can be used by non-hub
> >> devices as well.
> >>
> >> To account for the hub-specific code, add a flag to the device data
> >> structure and check its value for hub-specific code.
> > 
> > Please mention that the driver doesn't power off non-hub devices
> > during system suspend.
> > 
> >> Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
> >> ---
> >>  drivers/usb/misc/onboard_usb_dev.c |  3 ++-
> >>  drivers/usb/misc/onboard_usb_dev.h | 10 ++++++++++
> >>  2 files changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/usb/misc/onboard_usb_dev.c b/drivers/usb/misc/onboard_usb_dev.c
> >> index 2103af2cb2a6..f43130a6786f 100644
> >> --- a/drivers/usb/misc/onboard_usb_dev.c
> >> +++ b/drivers/usb/misc/onboard_usb_dev.c
> >> @@ -129,7 +129,8 @@ static int __maybe_unused onboard_dev_suspend(struct device *dev)
> >>  		if (!device_may_wakeup(node->udev->bus->controller))
> >>  			continue;
> >>  
> >> -		if (usb_wakeup_enabled_descendants(node->udev)) {
> >> +		if (usb_wakeup_enabled_descendants(node->udev) ||
> >> +		    !onboard_dev->pdata->is_hub) {
> > 
> > 
> > This check isn't dependent on characteristics of the USB devices processed
> > in this loop, therefore it can be performed at function entry. Please combine
> > it with the check of 'always_powered_in_suspend'. It's also an option to
> > omit the check completely, 'always_powered_in_suspend' will never be set for
> > non-hub devices (assuming the sysfs attribute isn't added).
> > 
> 
> The attribute will not be available for non-hub devices in v5. However,
> if the check is completely removed, will power_off not stay true at the
> end of the function, always leading to a device power off? As you said,
> 'always_powered_in_suspend' will not be set for non-hub devices.

Even without the sysfs attribute the field 'always_powered_in_suspend' could
be set to true by probe() for non-hub devices.