clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED

[PATCH] clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED

Posted by Mark Brown 1 month, 3 weeks ago

From: Maíra Canal <mcanal@igalia.com>

On Raspberry Pi 3B, the VEC clock is used by the VideoCore firmware
display driver, which remains active until the vc4 driver loads and
sends NOTIFY_DISPLAY_DONE. If this clock is disabled during boot, a bus
lockup happens and the firmware becomes unresponsive, causing a complete
system lockup.

Mark the VEC clock with CLK_IGNORE_UNUSED so it survives the unused
clock disablement and remains available until the vc4 driver takes over
display management.

Fixes: 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/unprepare callbacks")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/r/5f0bec08-f458-4fba-8bf3-06817a100c4c@sirena.org.uk
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patch.msgid.link/20260401111416.562279-2-mcanal@igalia.com
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
Resending this fix directly in the hope of getting it into -rc1 since
this is a clear boot regression and neither the original report nor the
fix have had any response for some reason.
---
 drivers/clk/bcm/clk-raspberrypi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
index df2d246eb6ef..f1a99de6de4f 100644
--- a/drivers/clk/bcm/clk-raspberrypi.c
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -160,6 +160,13 @@ raspberrypi_clk_variants[RPI_FIRMWARE_NUM_CLK_ID] = {
 	[RPI_FIRMWARE_VEC_CLK_ID] = {
 		.export = true,
 		.minimize = true,
+
+		/*
+		 * If this clock is disabled during boot, it causes a bus
+		 * lockup in RPi 3B. Therefore, make sure it's left enabled
+		 * during boot.
+		 */
+		.flags = CLK_IGNORE_UNUSED,
 	},
 	[RPI_FIRMWARE_DISP_CLK_ID] = {
 		.export = true,

---
base-commit: 672299736af6c398e867782708b7400957e62c76
change-id: 20260423-clk-bcm-fix-pi3-24feb4f409fd

Best regards,
--  
Mark Brown <broonie@kernel.org>

Re: [PATCH] clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED

Posted by Stephen Boyd 1 month, 3 weeks ago

Quoting Mark Brown (2026-04-24 08:34:52)
> From: Maíra Canal <mcanal@igalia.com>
> 
> On Raspberry Pi 3B, the VEC clock is used by the VideoCore firmware
> display driver, which remains active until the vc4 driver loads and
> sends NOTIFY_DISPLAY_DONE. If this clock is disabled during boot, a bus
> lockup happens and the firmware becomes unresponsive, causing a complete
> system lockup.
> 
> Mark the VEC clock with CLK_IGNORE_UNUSED so it survives the unused
> clock disablement and remains available until the vc4 driver takes over
> display management.
> 
> Fixes: 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/unprepare callbacks")
> Reported-by: Mark Brown <broonie@kernel.org>
> Closes: https://lore.kernel.org/r/5f0bec08-f458-4fba-8bf3-06817a100c4c@sirena.org.uk
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> Link: https://patch.msgid.link/20260401111416.562279-2-mcanal@igalia.com
> Tested-by: Mark Brown <broonie@kernel.org>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---

Applied to clk-fixes

Re: [PATCH] clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED

Posted by Brian Masney 1 month, 3 weeks ago

On Fri, Apr 24, 2026 at 11:37 AM Mark Brown <broonie@kernel.org> wrote:
> From: Maíra Canal <mcanal@igalia.com>
>
> On Raspberry Pi 3B, the VEC clock is used by the VideoCore firmware
> display driver, which remains active until the vc4 driver loads and
> sends NOTIFY_DISPLAY_DONE. If this clock is disabled during boot, a bus
> lockup happens and the firmware becomes unresponsive, causing a complete
> system lockup.
>
> Mark the VEC clock with CLK_IGNORE_UNUSED so it survives the unused
> clock disablement and remains available until the vc4 driver takes over
> display management.
>
> Fixes: 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/unprepare callbacks")
> Reported-by: Mark Brown <broonie@kernel.org>
> Closes: https://lore.kernel.org/r/5f0bec08-f458-4fba-8bf3-06817a100c4c@sirena.org.uk
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> Link: https://patch.msgid.link/20260401111416.562279-2-mcanal@igalia.com
> Tested-by: Mark Brown <broonie@kernel.org>
> Signed-off-by: Mark Brown <broonie@kernel.org>

Acked-by: Brian Masney <bmasney@redhat.com> # Active contributor to clk

I agree that this would be great to go in direct if possible.