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

[Ying Liu]

Hi,

On Wednesday, September 20, 2023 6:31 PM Lucas Stach <l.stach at pengutronix.de> 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)

" checkpatch.pl --strict" complains:
CHECK: Alignment should match open parenthesis
#31: FILE: drivers/gpu/drm/mxsfb/lcdif_drv.c:34:
+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);

This additional check looks fine, but it's done for every commit.
Is it ok to move it to lcdif_plane_atomic_check() where mode_changed
is set for those commits in question?

Regards,
Liu Ying

> +}
> +
>  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,
> --
> 2.39.2