[PATCH 5/5] drm: lcdif: force modeset when FB format changes

[Marek Vasut]

On 9/20/23 12:31, Lucas Stach wrote:
> Force a modeset if the new FB has a different format than the
> currently active one. While it might be possible to change between
> compatible formats without a full modeset as the format control is
> also supposed to be double buffered, the colorspace conversion is
> not, so when the CSC changes we need a modeset.
> 
> For now just always force a modeset when the FB format changes to
> properly reconfigure all parts of the device for the new format.
> 
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> ---
>   drivers/gpu/drm/mxsfb/lcdif_drv.c | 18 +++++++++++++++++-
>   drivers/gpu/drm/mxsfb/lcdif_kms.c | 26 ++++++++++++++++++++------
>   2 files changed, 37 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/lcdif_drv.c b/drivers/gpu/drm/mxsfb/lcdif_drv.c
> index 18de2f17e249..b74f0cf1e240 100644
> --- a/drivers/gpu/drm/mxsfb/lcdif_drv.c
> +++ b/drivers/gpu/drm/mxsfb/lcdif_drv.c
> @@ -30,9 +30,25 @@
>   #include "lcdif_drv.h"
>   #include "lcdif_regs.h"
>   
> +static int lcdif_atomic_check(struct drm_device *dev,
> +				struct drm_atomic_state *state)
> +{
> +	int ret;
> +
> +	ret = drm_atomic_helper_check(dev, state);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Check modeset again in case crtc_state->mode_changed is
> +	 * updated in plane's ->atomic_check callback.
> +	 */
> +	return drm_atomic_helper_check_modeset(dev, state);
> +}
> +
>   static const struct drm_mode_config_funcs lcdif_mode_config_funcs = {
>   	.fb_create		= drm_gem_fb_create,
> -	.atomic_check		= drm_atomic_helper_check,
> +	.atomic_check		= lcdif_atomic_check,
>   	.atomic_commit		= drm_atomic_helper_commit,
>   };
>   
> diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> index 3ebf55d06027..8167604bd3f8 100644
> --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> @@ -647,18 +647,32 @@ static const struct drm_crtc_funcs lcdif_crtc_funcs = {
>   static int lcdif_plane_atomic_check(struct drm_plane *plane,
>   				    struct drm_atomic_state *state)
>   {
> -	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state,
> -									     plane);
> +	struct drm_plane_state *new_state = drm_atomic_get_new_plane_state(state,
> +									   plane);
> +	struct drm_plane_state *old_state = drm_atomic_get_old_plane_state(state,
> +									   plane);
>   	struct lcdif_drm_private *lcdif = to_lcdif_drm_private(plane->dev);
>   	struct drm_crtc_state *crtc_state;
> +	int ret;
> +
> +	/* always okay to disable the plane */
> +	if (!new_state->fb)
> +		return 0;
>   
>   	crtc_state = drm_atomic_get_new_crtc_state(state,
>   						   &lcdif->crtc);
>   
> -	return drm_atomic_helper_check_plane_state(plane_state, crtc_state,
> -						   DRM_PLANE_NO_SCALING,
> -						   DRM_PLANE_NO_SCALING,
> -						   false, true);
> +	ret = drm_atomic_helper_check_plane_state(new_state, crtc_state,
> +						  DRM_PLANE_NO_SCALING,
> +						  DRM_PLANE_NO_SCALING,
> +						  false, true);
> +	if (ret)
> +		return ret;
> +
> +	if (old_state->fb && new_state->fb->format != old_state->fb->format)
> +		crtc_state->mode_changed = true;
> +
> +	return 0;
>   }
>   
>   static void lcdif_plane_primary_atomic_update(struct drm_plane *plane,

Reviewed-by: Marek Vasut <marex at denx.de>