linux-kernel - Re: [PATCH v3 2/7] usb: misc: onboard_dev: add support for non-hub devices

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Date: Wed, 21 Feb 2024 18:33:09 +0000
From: Matthias Kaehlcke <mka@...omium.org>
To: Javier Carrasco <javier.carrasco@...fvision.net>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v3 2/7] usb: misc: onboard_dev: add support for non-hub
 devices

On Tue, Feb 13, 2024 at 11:00:43AM +0100, Javier Carrasco wrote:
> On 06.02.24 19:40, Matthias Kaehlcke wrote:
> > On Tue, Feb 06, 2024 at 02:59:30PM +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.
> >>
> >> Signed-off-by: Javier Carrasco <javier.carrasco@...fvision.net>
> >> ---
> >>  drivers/usb/misc/onboard_usb_dev.c |  3 +++
> >>  drivers/usb/misc/onboard_usb_dev.h | 10 ++++++++++
> >>  2 files changed, 13 insertions(+)
> >>
> >> diff --git a/drivers/usb/misc/onboard_usb_dev.c b/drivers/usb/misc/onboard_usb_dev.c
> >> index e2e1e1e30c1e..3ac21ec38ac0 100644
> >> --- a/drivers/usb/misc/onboard_usb_dev.c
> >> +++ b/drivers/usb/misc/onboard_usb_dev.c
> >> @@ -123,6 +123,9 @@ static int __maybe_unused onboard_dev_suspend(struct device *dev)
> >>  	if (onboard_dev->always_powered_in_suspend)
> >>  		return 0;
> >>  
> >> +	if (!onboard_dev->pdata->is_hub)
> >> +		return onboard_dev_power_off(onboard_dev);
> > 
> > Why turn the device always off when it isn't a hub? It could be a device
> > with wakeup support.
> > 
> > I really regret making 'off in suspend' the default :(
> > 
> 
> 
> The power management seems to be a critical point to consider.
> 
> Maybe we keep the current implementation and add support to non-hub
> devices by simply adding a check to set power_off to false:
> 
> static int __maybe_unused onboard_dev_suspend(struct device *dev)
> 
> {
> 
>         struct onboard_dev *onboard_dev = dev_get_drvdata(dev);
> 
>         struct usbdev_node *node;
> 
>         bool power_off = true;
> 
> 
> 
>         if (onboard_dev->always_powered_in_suspend)
> 
>                 return 0;
> 
> 
> 
>         mutex_lock(&onboard_dev->lock);
> 
> 
> 
>         list_for_each_entry(node, &onboard_dev->udev_list, list) {
> 
>                 if (!device_may_wakeup(node->udev->bus->controller))
> 
>                         continue;
> 
> 
> 
> ~                if (usb_wakeup_enabled_descendants(node->udev) ||
> 
> +                    !onboard_dev->pdata->is_hub) {
> 
>                         power_off = false;
> 
>                         break;
> 
>                 }

It isn't really necessary to perform this check in the loop, it isn't
dependent on any properties of the USB devices, right? It could be
combined with the check of 'always_powered_in_suspend' above.