Re: [PATCH v3] media: bcm2835-unicam: Fix log status runtime access

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Thu, Jun 11, 2026 at 08:18:10PM +0300, Eugen Hristev wrote:
> On 6/11/26 11:03, Laurent Pinchart wrote:
> > On Thu, Jun 11, 2026 at 08:29:55AM +0300, Eugen Hristev wrote:
> >> When requesting log status, the block might be powered off, but registers
> >> are being read.
> >> Avoid reading the registers if the device is not resumed, thus also avoid
> >> powering up the device just for log status.
> >>
> >> Fixes: 392cd78d495f ("media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface")
> >> Signed-off-by: Eugen Hristev <ehristev@kernel.org>
> >> ---
> >> Changes in v3:
> >> - Changed to check return value of pm_runtime_get_if_active() and only call
> >>   pm_runtime_put() if the device is active.
> >> - Link to v2: https://patch.msgid.link/20260522-bcmpipm-v2-1-a3da66cbc9f0@kernel.org
> >>
> >> Changes in v2:
> >> - changed to use pm_runtime_get_if_active()
> >> - add corresponding put()
> >> - Link to v1: https://patch.msgid.link/20260521-bcmpipm-v1-1-3eba88d88045@kernel.org
> >>
> >> To: Raspberry Pi Kernel Maintenance <kernel-list@raspberrypi.com>
> >> To: Mauro Carvalho Chehab <mchehab@kernel.org>
> >> To: Florian Fainelli <florian.fainelli@broadcom.com>
> >> To: Ray Jui <rjui@broadcom.com>
> >> To: Scott Branden <sbranden@broadcom.com>
> >> To: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
> >> To: Sakari Ailus <sakari.ailus@linux.intel.com>
> >> To: Jean-Michel Hautbois <jeanmichel.hautbois@yoseli.org>
> >> To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >> To: Hans Verkuil <hverkuil@kernel.org>
> >> To: Naushir Patuck <naush@raspberrypi.com>
> >> Cc: Dave Stevenson <dave.stevenson@raspberrypi.com>
> >> Cc: linux-media@vger.kernel.org
> >> Cc: linux-rpi-kernel@lists.infradead.org
> >> Cc: linux-arm-kernel@lists.infradead.org
> >> Cc: linux-kernel@vger.kernel.org
> >> ---
> >>  drivers/media/platform/broadcom/bcm2835-unicam.c | 12 ++++++++++++
> >>  1 file changed, 12 insertions(+)
> >>
> >> diff --git a/drivers/media/platform/broadcom/bcm2835-unicam.c b/drivers/media/platform/broadcom/bcm2835-unicam.c
> >> index 8d28ba0b59a3..96b51e29bba4 100644
> >> --- a/drivers/media/platform/broadcom/bcm2835-unicam.c
> >> +++ b/drivers/media/platform/broadcom/bcm2835-unicam.c
> >> @@ -2043,6 +2043,7 @@ static int unicam_log_status(struct file *file, void *fh)
> >>  	struct unicam_node *node = video_drvdata(file);
> >>  	struct unicam_device *unicam = node->dev;
> >>  	u32 reg;
> >> +	int pm_active;
> >>  
> >>  	/* status for sub devices */
> >>  	v4l2_device_call_all(&unicam->v4l2_dev, 0, core, log_status);
> >> @@ -2052,6 +2053,14 @@ static int unicam_log_status(struct file *file, void *fh)
> >>  		 node->fmt.fmt.pix.width, node->fmt.fmt.pix.height);
> >>  	dev_info(unicam->dev, "V4L2 format:         %08x\n",
> >>  		 node->fmt.fmt.pix.pixelformat);
> >> +
> >> +	pm_active = pm_runtime_get_if_active(unicam->dev);
> >> +	if (!pm_active) {
> >> +		dev_info(unicam->dev,
> >> +			 "Live data N/A due to device inactive\n");
> >> +		return 0;
> >> +	}
> >> +
> >>  	reg = unicam_reg_read(unicam, UNICAM_IPIPE);
> >>  	dev_info(unicam->dev, "Unpacking/packing:   %u / %u\n",
> >>  		 unicam_get_field(reg, UNICAM_PUM_MASK),
> >> @@ -2065,6 +2074,9 @@ static int unicam_log_status(struct file *file, void *fh)
> >>  	dev_info(unicam->dev, "Write pointer:       %08x\n",
> >>  		 unicam_reg_read(unicam, UNICAM_IBWP));
> >>  
> >> +	if (pm_active == 1)
> >> +		pm_runtime_put(unicam->dev);
> > 
> > As far as I understand, the discussion on v2 concluded there was no need
> > to test pm_active here. Did I miss anything ?
> 
> Sorry, I saw the message from Sakari and he was pretty confident on the
> right way, he even mentioned that all sensors should be fixed, and has
> not come up with a follow up since.
> If v2 is the right way, please disregard this v3

Let's see what Sakari has to say :-)

> >> +
> >>  	return 0;
> >>  }
> >>  
> >>
> >> ---
> >> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
> >> change-id: 20260521-bcmpipm-6c578e73239c

-- 
Regards,

Laurent Pinchart