linux-kernel - Re: [PATCH v4 3/4] media: raspberrypi: Add support for RP1-CFE

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Message-ID: <49e375a3-d8e4-4b58-9456-1e6395b02a07@ideasonboard.com>
Date: Tue, 10 Sep 2024 12:56:38 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Jacopo Mondi <jacopo.mondi@...asonboard.com>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>,
 Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Florian Fainelli <florian.fainelli@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, oe-kbuild-all@...ts.linux.dev,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, Naushir Patuck
 <naush@...pberrypi.com>, Kieran Bingham <kieran.bingham@...asonboard.com>,
 kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v4 3/4] media: raspberrypi: Add support for RP1-CFE

On 10/09/2024 12:19, Jacopo Mondi wrote:

> However, I think this current patch is correct (assuming the above
> reasoning on i2c sensor drivers is correct) and doesn't require
> CONFIG_PM, so I would be tempted to keep this version.

I think the existence of this discussion alone proves my point that we 
should only support PM-case, unless !PM is a requirement =).

But if you do want to keep !PM:

Is there a reason why not mark the device as active with 
pm_runtime_set_active() after calling pispbe_runtime_resume and before 
accessing the device? That feels like the most logical way to use the 
function, and it would be right regardless whether the core will enable 
the parents before probe() or not.

And not related to the BE or CFE drivers, but it strikes me odd that to 
support PM and !PM we need to play with these tricks. I think the core 
should just do the right thing if the driver does pm_runtime_get_sync() 
even with !PM (although maybe the time has passed to be able to do that).

  Tomi