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

[Maíra Canal]

Hi Stephen,

It would be great to land this patch in the next release together with
commit 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/
unprepare callbacks"). When possible, could you take a look at it?

Best regards,
- Maíra

On 4/1/26 08:13, Maíra Canal wrote:
> 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 at kernel.org>
> Signed-off-by: Maíra Canal <mcanal at igalia.com>
> ---
>   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,