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

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

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 ?

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

-- 
Regards,

Laurent Pinchart