drm/sun4i: backend: Support YUV planes

Now that we have the guarantee that we will have only a single YUV plane,
actually support them. The way it works is not really straightforward,
since we first need to enable the YUV mode in the plane that we want to
setup, and then we have a few registers to setup the YUV buffer and
parameters.

We also need to setup the color correction to actually have something
displayed.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/66088c1398bd3189123f28a89a7ccc669fe9f296.1519931807.git-series.maxime.ripard@bootlin.com

1 files changed, 98 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
index 8aaa74d..9bad54f 100644
--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -42,6 +42,24 @@ static const u32 sunxi_rgb2yuv_coef[12] = {
 	0x000001c1, 0x00003e88, 0x00003fb8, 0x00000808
 };
 
+/*
+ * These coefficients are taken from the A33 BSP from Allwinner.
+ *
+ * The formula is for each component, each coefficient being multiplied by
+ * 1024 and each constant being multiplied by 16:
+ * G = 1.164 * Y - 0.391 * U - 0.813 * V + 135
+ * R = 1.164 * Y + 1.596 * V - 222
+ * B = 1.164 * Y + 2.018 * U + 276
+ *
+ * This seems to be a conversion from Y[16:235] UV[16:240] to RGB[0:255],
+ * following the BT601 spec.
+ */
+static const u32 sunxi_bt601_yuv2rgb_coef[12] = {
+	0x000004a7, 0x00001e6f, 0x00001cbf, 0x00000877,
+	0x000004a7, 0x00000000, 0x00000662, 0x00003211,
+	0x000004a7, 0x00000812, 0x00000000, 0x00002eb1,
+};
+
 static inline bool sun4i_backend_format_is_planar_yuv(uint32_t format)
 {
 	switch (format) {
@@ -198,6 +216,61 @@ int sun4i_backend_update_layer_coord(struct sun4i_backend *backend,
 	return 0;
 }
 
+static int sun4i_backend_update_yuv_format(struct sun4i_backend *backend,
+					   int layer, struct drm_plane *plane)
+{
+	struct drm_plane_state *state = plane->state;
+	struct drm_framebuffer *fb = state->fb;
+	uint32_t format = fb->format->format;
+	u32 val = SUN4I_BACKEND_IYUVCTL_EN;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(sunxi_bt601_yuv2rgb_coef); i++)
+		regmap_write(backend->engine.regs,
+			     SUN4I_BACKEND_YGCOEF_REG(i),
+			     sunxi_bt601_yuv2rgb_coef[i]);
+
+	/*
+	 * We should do that only for a single plane, but the
+	 * framebuffer's atomic_check has our back on this.
+	 */
+	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN,
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN);
+
+	/* TODO: Add support for the multi-planar YUV formats */
+	if (sun4i_backend_format_is_packed_yuv422(format))
+		val |= SUN4I_BACKEND_IYUVCTL_FBFMT_PACKED_YUV422;
+	else
+		DRM_DEBUG_DRIVER("Unsupported YUV format (0x%x)\n", format);
+
+	/*
+	 * Allwinner seems to list the pixel sequence from right to left, while
+	 * DRM lists it from left to right.
+	 */
+	switch (format) {
+	case DRM_FORMAT_YUYV:
+		val |= SUN4I_BACKEND_IYUVCTL_FBPS_VYUY;
+		break;
+	case DRM_FORMAT_YVYU:
+		val |= SUN4I_BACKEND_IYUVCTL_FBPS_UYVY;
+		break;
+	case DRM_FORMAT_UYVY:
+		val |= SUN4I_BACKEND_IYUVCTL_FBPS_YVYU;
+		break;
+	case DRM_FORMAT_VYUY:
+		val |= SUN4I_BACKEND_IYUVCTL_FBPS_YUYV;
+		break;
+	default:
+		DRM_DEBUG_DRIVER("Unsupported YUV pixel sequence (0x%x)\n",
+				 format);
+	}
+
+	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVCTL_REG, val);
+
+	return 0;
+}
+
 int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 				       int layer, struct drm_plane *plane)
 {
@@ -207,6 +280,10 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 	u32 val;
 	int ret;
 
+	/* Clear the YUV mode */
+	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN, 0);
+
 	if (plane->state->crtc)
 		interlaced = plane->state->crtc->state->adjusted_mode.flags
 			& DRM_MODE_FLAG_INTERLACE;
@@ -218,6 +295,9 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 	DRM_DEBUG_DRIVER("Switching display backend interlaced mode %s\n",
 			 interlaced ? "on" : "off");
 
+	if (sun4i_backend_format_is_yuv(fb->format->format))
+		return sun4i_backend_update_yuv_format(backend, layer, plane);
+
 	ret = sun4i_backend_drm_format_to_layer(fb->format->format, &val);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Invalid format\n");
@@ -255,6 +335,21 @@ int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
 	return 0;
 }
 
+static int sun4i_backend_update_yuv_buffer(struct sun4i_backend *backend,
+					   struct drm_framebuffer *fb,
+					   dma_addr_t paddr)
+{
+	/* TODO: Add support for the multi-planar YUV formats */
+	DRM_DEBUG_DRIVER("Setting packed YUV buffer address to %pad\n", &paddr);
+	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVADD_REG(0), paddr);
+
+	DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
+	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVLINEWIDTH_REG(0),
+		     fb->pitches[0] * 8);
+
+	return 0;
+}
+
 int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 				      int layer, struct drm_plane *plane)
 {
@@ -280,6 +375,9 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
 	 */
 	paddr -= PHYS_OFFSET;
 
+	if (sun4i_backend_format_is_yuv(fb->format->format))
+		return sun4i_backend_update_yuv_buffer(backend, fb, paddr);
+
 	/* Write the 32 lower bits of the address (in bits) */
 	lo_paddr = paddr << 3;
 	DRM_DEBUG_DRIVER("Setting address lower bits to 0x%x\n", lo_paddr);