linux-kernel - [PATCH 08/30] drm/sun4i: ui layer: Write attributes in one go

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Message-ID: <20251012192330.6903-9-jernej.skrabec@gmail.com>
Date: Sun, 12 Oct 2025 21:23:08 +0200
From: Jernej Skrabec <jernej.skrabec@...il.com>
To: mripard@...nel.org,
	wens@...e.org
Cc: maarten.lankhorst@...ux.intel.com,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	samuel@...lland.org,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-sunxi@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Jernej Skrabec <jernej.skrabec@...il.com>
Subject: [PATCH 08/30] drm/sun4i: ui layer: Write attributes in one go

It turns out that none of the UI channel registers were meant to be
read. Mostly it works fine but sometimes it returns incorrect values.

Rework UI layer code to write all registers in one go to avoid reads.

This rework will also allow proper code separation.

Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
---
 drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 50 +++++++++-----------------
 1 file changed, 16 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
index 12c83c54f9bc..8634d2ee613a 100644
--- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
@@ -25,25 +25,27 @@
 #include "sun8i_ui_scaler.h"
 #include "sun8i_vi_scaler.h"
 
-static void sun8i_ui_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
-					int overlay, struct drm_plane *plane)
+static void sun8i_ui_layer_update_attributes(struct sun8i_mixer *mixer,
+					     int channel, int overlay,
+					     struct drm_plane *plane)
 {
-	u32 mask, val, ch_base;
+	struct drm_plane_state *state = plane->state;
+	const struct drm_format_info *fmt;
+	u32 val, ch_base, hw_fmt;
 
 	ch_base = sun8i_channel_base(mixer, channel);
+	fmt = state->fb->format;
+	sun8i_mixer_drm_format_to_hw(fmt->format, &hw_fmt);
 
-	mask = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_MASK |
-		SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MASK;
-
-	val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(plane->state->alpha >> 8);
-
-	val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
+	val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(state->alpha >> 8);
+	val |= (state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
 		SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_PIXEL :
 		SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_COMBINED;
+	val |= hw_fmt << SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_OFFSET;
+	val |= SUN8I_MIXER_CHAN_UI_LAYER_ATTR_EN;
 
-	regmap_update_bits(mixer->engine.regs,
-			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR(ch_base, overlay),
-			   mask, val);
+	regmap_write(mixer->engine.regs,
+		     SUN8I_MIXER_CHAN_UI_LAYER_ATTR(ch_base, overlay), val);
 }
 
 static void sun8i_ui_layer_update_coord(struct sun8i_mixer *mixer, int channel,
@@ -111,24 +113,6 @@ static void sun8i_ui_layer_update_coord(struct sun8i_mixer *mixer, int channel,
 	}
 }
 
-static void sun8i_ui_layer_update_formats(struct sun8i_mixer *mixer, int channel,
-					  int overlay, struct drm_plane *plane)
-{
-	struct drm_plane_state *state = plane->state;
-	const struct drm_format_info *fmt;
-	u32 val, ch_base, hw_fmt;
-
-	ch_base = sun8i_channel_base(mixer, channel);
-
-	fmt = state->fb->format;
-	sun8i_mixer_drm_format_to_hw(fmt->format, &hw_fmt);
-
-	val = hw_fmt << SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_OFFSET;
-	regmap_update_bits(mixer->engine.regs,
-			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR(ch_base, overlay),
-			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_MASK, val);
-}
-
 static void sun8i_ui_layer_update_buffer(struct sun8i_mixer *mixer, int channel,
 					 int overlay, struct drm_plane *plane)
 {
@@ -220,12 +204,10 @@ static void sun8i_ui_layer_atomic_update(struct drm_plane *plane,
 	if (!new_state->crtc || !new_state->visible)
 		return;
 
+	sun8i_ui_layer_update_attributes(mixer, layer->channel,
+					 layer->overlay, plane);
 	sun8i_ui_layer_update_coord(mixer, layer->channel,
 				    layer->overlay, plane);
-	sun8i_ui_layer_update_alpha(mixer, layer->channel,
-				    layer->overlay, plane);
-	sun8i_ui_layer_update_formats(mixer, layer->channel,
-				      layer->overlay, plane);
 	sun8i_ui_layer_update_buffer(mixer, layer->channel,
 				     layer->overlay, plane);
 }
-- 
2.51.0