Re: [PATCH v3 1/2] drm/imx/lcdc: avoid duplicate clk_per enable

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Calls to sleeping functions (`clk_prepare_enable` and `clk_disable_unprepare`) from the plane atomic update and CRTC enable/disable callbacks, violating DRM atomic context requirements.
--

--- Patch [1]: [PATCH v3 1/2] drm/imx/lcdc: avoid duplicate clk_per enable ---
commit 48c4f154b28e9de1d485ea56766c8a24df823739
Author: Ze Huang <ze.huang@oss.qualcomm.com>

drm/imx/lcdc: avoid duplicate clk_per enable

The simple-KMS helper calls the pipe update after enabling the CRTC,
which causes imx_lcdc_update_hw_registers() to be called again. This
patch avoids the duplicate clock enable by skipping the register update
when the CRTC already needs a modeset.

> diff --git a/drivers/gpu/drm/imx/lcdc/imx-lcdc.c b/drivers/gpu/drm/imx/lcdc/imx-lcdc.c
> index c67fe80b8115e..e00e52c1c46ec 100644
> --- a/drivers/gpu/drm/imx/lcdc/imx-lcdc.c
> +++ b/drivers/gpu/drm/imx/lcdc/imx-lcdc.c
> @@ -310,7 +310,8 @@ static void imx_lcdc_pipe_update(struct drm_simple_display_pipe *pipe,
>  	else if (old_crtc != crtc)
>  		mode_changed = true;
>  
> -	imx_lcdc_update_hw_registers(pipe, old_state, mode_changed);
> +	if (!drm_atomic_crtc_needs_modeset(crtc->state))
> +		imx_lcdc_update_hw_registers(pipe, old_state, mode_changed);

[Severity: High]
This is a pre-existing issue, but does calling imx_lcdc_update_hw_registers()
from imx_lcdc_pipe_update() risk sleeping in an atomic context?

imx_lcdc_pipe_update() acts as a plane atomic update callback, which executes
in an atomic context where sleeping is forbidden. However, it calls
imx_lcdc_update_hw_registers(), which in turn calls sleeping functions:

imx_lcdc_update_hw_registers() {
    ...
    clk_disable_unprepare(lcdc->clk_per);
    ...
    clk_prepare_enable(lcdc->clk_per);
    ...
}

Will this cause 'scheduling while atomic' panics when a plane format changes
without a full modeset?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727-drm-simple-kms-removal-v3-0-de36e534f7a1@oss.qualcomm.com?part=1