Re: [PATCH v3 6/8] drm/repaper: replace struct drm_simple_display_pipe with regular atomic helpers

["Ze Huang" <ze.huang@oss.qualcomm.com>]

On Mon Jul 27, 2026 at 4:04 AM CST, sashiko-bot wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
>
> Pre-existing issues:
> - [High] Sleeping functions and blocking memory allocations are called from within CRTC and plane atomic callbacks, violating atomic context constraints.
> --
>
> --- Patch [6]: [PATCH v3 6/8] drm/repaper: replace struct drm_simple_display_pipe with regular atomic helpers ---
> commit c95d4b930f0cb70a4eb89a2c19785d09216e66c1
> Author: Ze Huang <ze.huang@oss.qualcomm.com>
>
> drm/repaper: replace struct drm_simple_display_pipe with regular atomic helpers
>
> This commit converts the repaper driver to use explicit primary plane, CRTC,
> and encoder objects instead of the simple display pipe helpers. It retains
> the shadow-plane helpers, framebuffer access handling, and no-scaling
> plane-state validation from the simple-KMS path.
>
>> diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/repaper.c
>> index c8270591afc7f..f225e38fd4045 100644
>> --- a/drivers/gpu/drm/tiny/repaper.c
>> +++ b/drivers/gpu/drm/tiny/repaper.c
>
> [ ... ]
>
>> -static void repaper_pipe_enable(struct drm_simple_display_pipe *pipe,
>> -				struct drm_crtc_state *crtc_state,
>> -				struct drm_plane_state *plane_state)
>> +static void repaper_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>> +					      struct drm_atomic_commit *commit)
>>  {
>> -	struct repaper_epd *epd = drm_to_epd(pipe->crtc.dev);
>> +	struct repaper_epd *epd = drm_to_epd(crtc->dev);
>>  	struct spi_device *spi = epd->spi;
>>  	struct device *dev = &spi->dev;
>>  	bool dc_ok = false;
>>  	int i, ret, idx;
>>  
>> -	if (!drm_dev_enter(pipe->crtc.dev, &idx))
>> +	if (!drm_dev_enter(crtc->dev, &idx))
>>  		return;
>
> [Severity: High]
> This is a pre-existing issue, but does this function sleep in atomic context?
>
> CRTC atomic enable callbacks execute in atomic context where sleeping is
> forbidden. However, looking at the code, this function makes direct calls to
> sleeping functions:
>
>     gpiod_set_value_cansleep(epd->reset, 0);
>     ...
>     usleep_range(5000, 10000);
>
> Could this cause system instability or kernel panics during display state
> updates?

False positive

>
> [ ... ]
>
>> -static void repaper_pipe_disable(struct drm_simple_display_pipe *pipe)
>> +static void repaper_crtc_helper_atomic_disable(struct drm_crtc *crtc,
>> +					       struct drm_atomic_commit *commit)
>>  {
>> -	struct repaper_epd *epd = drm_to_epd(pipe->crtc.dev);
>> +	struct repaper_epd *epd = drm_to_epd(crtc->dev);
>>  	struct spi_device *spi = epd->spi;
>>  	unsigned int line;
>
> [Severity: High]
> This is a pre-existing issue, but similar to the enable callback, is it safe
> for this atomic disable callback to sleep?
>
> It calls functions that can sleep:
>
>     msleep(25);
>     gpiod_set_value_cansleep(epd->border, 0);
>     msleep(200);
>     ...
>     power_off(epd);
>
> [ ... ]

False positive

>
>> -static void repaper_pipe_update(struct drm_simple_display_pipe *pipe,
>> -				struct drm_plane_state *old_state)
>> +static void repaper_plane_helper_atomic_update(struct drm_plane *plane,
>> +					       struct drm_atomic_commit *commit)
>>  {
>> -	struct drm_plane_state *state = pipe->plane.state;
>> -	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
>> +	struct drm_plane_state *old_pstate = drm_atomic_get_old_plane_state(commit, plane);
>> +	struct drm_plane_state *pstate = drm_atomic_get_new_plane_state(commit, plane);
>> +	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(pstate);
>> +	struct drm_crtc_state *cstate = NULL;
>>  	struct drm_rect rect;
>>  
>> -	if (!pipe->crtc.state->active)
>> +	if (pstate->crtc)
>> +		cstate = drm_atomic_get_new_crtc_state(commit, pstate->crtc);
>> +
>> +	if (!cstate || !cstate->active)
>>  		return;
>>  
>> -	if (drm_atomic_helper_damage_merged(old_state, state, &rect))
>> -		repaper_fb_dirty(state->fb, shadow_plane_state->data,
>> +	if (drm_atomic_helper_damage_merged(old_pstate, pstate, &rect))
>> +		repaper_fb_dirty(pstate->fb, shadow_plane_state->data,
>>  				 &shadow_plane_state->fmtcnv_state);
>>  }
>
> [Severity: High]
> This is a pre-existing issue, but does repaper_fb_dirty() perform blocking
> memory allocations in atomic context?
>
> The plane atomic update callback must not sleep, but repaper_fb_dirty()
> uses GFP_KERNEL for memory allocation:
>
>     buf = kmalloc(fb->width * fb->height / 8, GFP_KERNEL);
>
> Should this allocation be moved outside of the atomic update path or use a
> non-blocking flag?

False positive