[PATCH v3 09/14] drm/solomon: ssd16xx: Expose color mode as plane property

[Devarsh Thakkar <devarsht@ti.com>]

Add a DRM plane property "color_mode" for panels that support
3-color (black/white/red) display modes.

The property allows runtime selection between:
  - bw (black/white): R1 format represents black (0) and white (1)
  - 3color: R1 format represents red ink (1) on white background

The property is created on all panels with "black-white" selectable;
panels with red_supported = true also expose the "3-color" option.
The default is set from the panel configuration's default_color_mode
field (typically BW for monochrome panels).

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
---
Changes in v3:
- Reject 3-color mode together with partial refresh in the plane
  atomic_check, as partial refresh does not update the red channel
- Only create the color_mode property on panels with a red plane instead
  of exposing a property with a single possible value
---
 drivers/gpu/drm/solomon/ssd16xx.c | 51 +++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/gpu/drm/solomon/ssd16xx.c b/drivers/gpu/drm/solomon/ssd16xx.c
index f53c67ae7d31..6037717635a4 100644
--- a/drivers/gpu/drm/solomon/ssd16xx.c
+++ b/drivers/gpu/drm/solomon/ssd16xx.c
@@ -399,6 +399,7 @@ struct ssd16xx_device {
 	u8  spi_buf[64] ____cacheline_aligned; /* DMA-safe buffer for SPI transfers */
 
 	struct drm_property *refresh_mode_property;
+	struct drm_property *color_mode_property;
 };
 
 /* Plane state subclass: refresh_mode lives on the plane, not the connector,
@@ -407,6 +408,7 @@ struct ssd16xx_device {
 struct ssd16xx_plane_state {
 	struct drm_shadow_plane_state base;
 	enum ssd16xx_refresh_mode refresh_mode; /* Pending refresh mode */
+	enum ssd16xx_color_mode color_mode;     /* Pending color mode */
 };
 
 #define to_ssd16xx_plane_state(s) \
@@ -1457,6 +1459,7 @@ static struct drm_plane_state *ssd16xx_plane_atomic_create_state(struct drm_plan
 
 	__drm_gem_shadow_plane_state_init(plane, &ssd_state->base);
 	ssd_state->refresh_mode = device->refresh_mode;
+	ssd_state->color_mode = device->color_mode;
 
 	return &ssd_state->base.base;
 }
@@ -1499,6 +1502,10 @@ static int ssd16xx_plane_atomic_get_property(struct drm_plane *plane,
 		*val = ssd_state->refresh_mode;
 		return 0;
 	}
+	if (property == device->color_mode_property) {
+		*val = ssd_state->color_mode;
+		return 0;
+	}
 	return -EINVAL;
 }
 
@@ -1516,6 +1523,18 @@ static int ssd16xx_plane_atomic_set_property(struct drm_plane *plane,
 		ssd_state->refresh_mode = val;
 		return 0;
 	}
+	if (property == device->color_mode_property) {
+		if (val > SSD16XX_COLOR_MODE_3COLOR)
+			return -EINVAL;
+		if (val == SSD16XX_COLOR_MODE_3COLOR &&
+		    !device->device_cfg->red_supported) {
+			drm_dbg(&device->drm,
+				"3-color not supported by this panel\n");
+			return -EINVAL;
+		}
+		ssd_state->color_mode = val;
+		return 0;
+	}
 	return -EINVAL;
 }
 
@@ -1535,11 +1554,20 @@ static int ssd16xx_plane_atomic_check(struct drm_plane *plane,
 {
 	struct drm_plane_state *new_plane_state =
 		drm_atomic_get_new_plane_state(state, plane);
+	struct ssd16xx_plane_state *ssd_state =
+		to_ssd16xx_plane_state(new_plane_state);
 	struct drm_crtc_state *crtc_state;
 
 	if (!new_plane_state->crtc)
 		return 0;
 
+	if (ssd_state->color_mode == SSD16XX_COLOR_MODE_3COLOR &&
+	    ssd_state->refresh_mode == SSD16XX_REFRESH_PARTIAL) {
+		drm_dbg_atomic(plane->dev,
+			       "3-color mode does not support partial refresh\n");
+		return -EINVAL;
+	}
+
 	crtc_state = drm_atomic_get_new_crtc_state(state, new_plane_state->crtc);
 
 	return drm_atomic_helper_check_plane_state(new_plane_state, crtc_state,
@@ -1608,6 +1636,7 @@ static void ssd16xx_plane_atomic_update(struct drm_plane *plane,
 	}
 
 	device->refresh_mode = new_ssd->refresh_mode;
+	device->color_mode = new_ssd->color_mode;
 
 	/*
 	 * When refresh_mode_init was set, use the specified mode for this first
@@ -1855,6 +1884,11 @@ static const struct drm_prop_enum_list ssd16xx_refresh_mode_enum[] = {
 	{ SSD16XX_REFRESH_FAST,    "fast"    },
 };
 
+static const struct drm_prop_enum_list ssd16xx_color_mode_enum[] = {
+	{ SSD16XX_COLOR_MODE_BW,     "black-white" },
+	{ SSD16XX_COLOR_MODE_3COLOR, "3-color"     },
+};
+
 static int ssd16xx_plane_create_properties(struct ssd16xx_device *device)
 {
 	struct drm_device *drm = &device->drm;
@@ -1869,6 +1903,23 @@ static int ssd16xx_plane_create_properties(struct ssd16xx_device *device)
 	drm_object_attach_property(plane_obj,
 				   device->refresh_mode_property,
 				   device->refresh_mode);
+
+	/*
+	 * Color mode: only meaningful on panels with a physical red plane.
+	 * BW-only panels get no property at all rather than a one-value knob.
+	 */
+	if (!device->device_cfg->red_supported)
+		return 0;
+
+	device->color_mode_property =
+		drm_property_create_enum(drm, 0, "color_mode",
+					 ssd16xx_color_mode_enum,
+					 ARRAY_SIZE(ssd16xx_color_mode_enum));
+	if (!device->color_mode_property)
+		return -ENOMEM;
+	drm_object_attach_property(plane_obj,
+				   device->color_mode_property,
+				   device->color_mode);
 	return 0;
 }
 
-- 
2.39.1