[PATCH v4] media: bcm2835-unicam: Fix log status runtime access

[Eugen Hristev]

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 at kernel.org>
---
Changes in v4:
- rebased on latest tree, no additional change.
- Link to v3: https://patch.msgid.link/20260611-bcmpipm-v3-1-c609dacb029f@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 at raspberrypi.com>
To: Mauro Carvalho Chehab <mchehab at kernel.org>
To: Florian Fainelli <florian.fainelli at broadcom.com>
To: Ray Jui <rjui at broadcom.com>
To: Scott Branden <sbranden at broadcom.com>
To: Broadcom internal kernel review list <bcm-kernel-feedback-list at broadcom.com>
To: Sakari Ailus <sakari.ailus at linux.intel.com>
To: Jean-Michel Hautbois <jeanmichel.hautbois at yoseli.org>
To: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
To: Hans Verkuil <hverkuil at kernel.org>
To: Naushir Patuck <naush at raspberrypi.com>
Cc: Dave Stevenson <dave.stevenson at raspberrypi.com>
Cc: linux-media at vger.kernel.org
Cc: linux-rpi-kernel at lists.infradead.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at 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 14bb916dd7b1..7745aee711cb 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);
+
 	return 0;
 }
 

---
base-commit: 903c1cf6dff9964e71eda98a39e2e5d442050472
change-id: 20260521-bcmpipm-6c578e73239c

Best regards,
--  
Eugen Hristev <ehristev at kernel.org>