linux-kernel - Re: [PATCH v5 6/8] usb: misc: onboard_dev: add support for non-hub devices

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Message-ID: <ecf303c3-d7a1-49d5-a997-32596215e43d@wolfvision.net>
Date: Wed, 28 Feb 2024 21:21:00 +0100
From: Javier Carrasco <javier.carrasco@...fvision.net>
To: Matthias Kaehlcke <mka@...omium.org>
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>,
 Helen Koike <helen.koike@...labora.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Russell King <linux@...linux.org.uk>, linux-sound@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 6/8] usb: misc: onboard_dev: add support for non-hub
 devices

On 28.02.24 19:10, Matthias Kaehlcke wrote:
> On Wed, Feb 28, 2024 at 02:51:33PM +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.
>>
>> The 'always_powered_in_supend' attribute is only available for hub
>> devices, keeping the driver's default behavior for non-hub devices (keep
>> on in suspend).
>>
>> Signed-off-by: Javier Carrasco <javier.carrasco@...fvision.net>
>> ---
>>  drivers/usb/misc/onboard_usb_dev.c | 25 +++++++++++++++++++++++--
>>  drivers/usb/misc/onboard_usb_dev.h | 10 ++++++++++
>>  2 files changed, 33 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/misc/onboard_usb_dev.c b/drivers/usb/misc/onboard_usb_dev.c
>> index e1779bd2d126..df0ed172c7ec 100644
>> --- a/drivers/usb/misc/onboard_usb_dev.c
>> +++ b/drivers/usb/misc/onboard_usb_dev.c
>> @@ -132,7 +132,8 @@ static int __maybe_unused onboard_dev_suspend(struct device *dev)
>>  	struct usbdev_node *node;
>>  	bool power_off = true;
>>  
>> -	if (onboard_dev->always_powered_in_suspend)
>> +	if (onboard_dev->always_powered_in_suspend &&
>> +	    !onboard_dev->pdata->is_hub)
>>  		return 0;
> 
> With this non-hub devices would always be powered down, since
> 'always_powerd_in_suspend' is not set for them. This should be:
> 

May I ask you what you meant in v4 with this comment?

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

>   if (!onboard_dev->pdata->is_hub ||
>        onboard_dev->always_powered_in_suspend)
> 
> Checking for the (non-)hub status first is clearer IMO, also it avoids
> an unneccessary check of 'always_powered' for non-hub devices.
> 

That makes sense and will be fixed.

> Without code context: for hubs there can be multiple device tree nodes
> for the same physical hub chip (e.g. one for the USB2 and another for
> the USB3 part). I suppose this could also be the case for non-hub
> devices. For hubs there is the 'peer-hub' device tree property to
> establish a link between the two USB devices, as a result the onboard
> driver only creates a single platform device (which is desired,
> otherwise two platform devices would be in charge for power sequencing
> the same phyiscal device. For non-hub devices there is currently no such
> link. In many cases I expect there will be just one DT entry even though
> the device has multiple USB interfaces, but it could happen and would
> actually be a more accurate representation.
> 
> General support is already there (the code dealing with 'peer-hub'), but
> we'd have to come up with a suitable name. 'peer-device' is the first
> thing that comes to my mind, but there might be better options. If such
> a generic property is added then we should deprecate 'peer-hub', but
> maintain backwards compatibility.

I have nothing against that, but the first non-hub device that will be
added does not have multiple DT nodes, so I have nothing to test that
extension with real hardware.

That could be added in the future, though, if the need ever arises.

Best regards,
Javier Carrasco