drm/format-helper: Add conversion from XRGB8888 to 15-bit RGB555 formats

Add conversion from XRGB8888 to XRGB1555, ARGB1555 and RGBA5551, which
are the formats currently supported by the simplefb infrastructure. The
new helpers allow the output of XRGB8888 framebuffers to firmware
scanout buffers in one of the 15-bit formats.

v3:
	* use __le* for destination buffers (Jose, kernel test robot)
v2:
	* test 15-bit results with local endianness (Jose)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230102112927.26565-10-tzimmermann@suse.de

1 files changed, 164 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
index 33780c9183bb..d631627e6c39 100644
--- a/drivers/gpu/drm/drm_format_helper.c
+++ b/drivers/gpu/drm/drm_format_helper.c
@@ -396,6 +396,161 @@ void drm_fb_xrgb8888_to_rgb565(struct iosys_map *dst, const unsigned int *dst_pi
 }
 EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb565);
 
+static void drm_fb_xrgb8888_to_xrgb1555_line(void *dbuf, const void *sbuf, unsigned int pixels)
+{
+	__le16 *dbuf16 = dbuf;
+	const __le32 *sbuf32 = sbuf;
+	unsigned int x;
+	u16 val16;
+	u32 pix;
+
+	for (x = 0; x < pixels; x++) {
+		pix = le32_to_cpu(sbuf32[x]);
+		val16 = ((pix & 0x00f80000) >> 9) |
+			((pix & 0x0000f800) >> 6) |
+			((pix & 0x000000f8) >> 3);
+		dbuf16[x] = cpu_to_le16(val16);
+	}
+}
+
+/**
+ * drm_fb_xrgb8888_to_xrgb1555 - Convert XRGB8888 to XRGB1555 clip buffer
+ * @dst: Array of XRGB1555 destination buffers
+ * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
+ *             within @dst; can be NULL if scanlines are stored next to each other.
+ * @src: Array of XRGB8888 source buffer
+ * @fb: DRM framebuffer
+ * @clip: Clip rectangle area to copy
+ *
+ * This function copies parts of a framebuffer to display memory and converts
+ * the color format during the process. The parameters @dst, @dst_pitch and
+ * @src refer to arrays. Each array must have at least as many entries as
+ * there are planes in @fb's format. Each entry stores the value for the
+ * format's respective color plane at the same index.
+ *
+ * This function does not apply clipping on @dst (i.e. the destination is at the
+ * top-left corner).
+ *
+ * Drivers can use this function for XRGB1555 devices that don't support
+ * XRGB8888 natively.
+ */
+void drm_fb_xrgb8888_to_xrgb1555(struct iosys_map *dst, const unsigned int *dst_pitch,
+				 const struct iosys_map *src, const struct drm_framebuffer *fb,
+				 const struct drm_rect *clip)
+{
+	static const u8 dst_pixsize[DRM_FORMAT_MAX_PLANES] = {
+		2,
+	};
+
+	drm_fb_xfrm(dst, dst_pitch, dst_pixsize, src, fb, clip, false,
+		    drm_fb_xrgb8888_to_xrgb1555_line);
+}
+EXPORT_SYMBOL(drm_fb_xrgb8888_to_xrgb1555);
+
+static void drm_fb_xrgb8888_to_argb1555_line(void *dbuf, const void *sbuf, unsigned int pixels)
+{
+	__le16 *dbuf16 = dbuf;
+	const __le32 *sbuf32 = sbuf;
+	unsigned int x;
+	u16 val16;
+	u32 pix;
+
+	for (x = 0; x < pixels; x++) {
+		pix = le32_to_cpu(sbuf32[x]);
+		val16 = BIT(15) | /* set alpha bit */
+			((pix & 0x00f80000) >> 9) |
+			((pix & 0x0000f800) >> 6) |
+			((pix & 0x000000f8) >> 3);
+		dbuf16[x] = cpu_to_le16(val16);
+	}
+}
+
+/**
+ * drm_fb_xrgb8888_to_argb1555 - Convert XRGB8888 to ARGB1555 clip buffer
+ * @dst: Array of ARGB1555 destination buffers
+ * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
+ *             within @dst; can be NULL if scanlines are stored next to each other.
+ * @src: Array of XRGB8888 source buffer
+ * @fb: DRM framebuffer
+ * @clip: Clip rectangle area to copy
+ *
+ * This function copies parts of a framebuffer to display memory and converts
+ * the color format during the process. The parameters @dst, @dst_pitch and
+ * @src refer to arrays. Each array must have at least as many entries as
+ * there are planes in @fb's format. Each entry stores the value for the
+ * format's respective color plane at the same index.
+ *
+ * This function does not apply clipping on @dst (i.e. the destination is at the
+ * top-left corner).
+ *
+ * Drivers can use this function for ARGB1555 devices that don't support
+ * XRGB8888 natively. It sets an opaque alpha channel as part of the conversion.
+ */
+void drm_fb_xrgb8888_to_argb1555(struct iosys_map *dst, const unsigned int *dst_pitch,
+				 const struct iosys_map *src, const struct drm_framebuffer *fb,
+				 const struct drm_rect *clip)
+{
+	static const u8 dst_pixsize[DRM_FORMAT_MAX_PLANES] = {
+		2,
+	};
+
+	drm_fb_xfrm(dst, dst_pitch, dst_pixsize, src, fb, clip, false,
+		    drm_fb_xrgb8888_to_argb1555_line);
+}
+EXPORT_SYMBOL(drm_fb_xrgb8888_to_argb1555);
+
+static void drm_fb_xrgb8888_to_rgba5551_line(void *dbuf, const void *sbuf, unsigned int pixels)
+{
+	__le16 *dbuf16 = dbuf;
+	const __le32 *sbuf32 = sbuf;
+	unsigned int x;
+	u16 val16;
+	u32 pix;
+
+	for (x = 0; x < pixels; x++) {
+		pix = le32_to_cpu(sbuf32[x]);
+		val16 = ((pix & 0x00f80000) >> 8) |
+			((pix & 0x0000f800) >> 5) |
+			((pix & 0x000000f8) >> 2) |
+			BIT(0); /* set alpha bit */
+		dbuf16[x] = cpu_to_le16(val16);
+	}
+}
+
+/**
+ * drm_fb_xrgb8888_to_rgba5551 - Convert XRGB8888 to RGBA5551 clip buffer
+ * @dst: Array of RGBA5551 destination buffers
+ * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
+ *             within @dst; can be NULL if scanlines are stored next to each other.
+ * @src: Array of XRGB8888 source buffer
+ * @fb: DRM framebuffer
+ * @clip: Clip rectangle area to copy
+ *
+ * This function copies parts of a framebuffer to display memory and converts
+ * the color format during the process. The parameters @dst, @dst_pitch and
+ * @src refer to arrays. Each array must have at least as many entries as
+ * there are planes in @fb's format. Each entry stores the value for the
+ * format's respective color plane at the same index.
+ *
+ * This function does not apply clipping on @dst (i.e. the destination is at the
+ * top-left corner).
+ *
+ * Drivers can use this function for RGBA5551 devices that don't support
+ * XRGB8888 natively. It sets an opaque alpha channel as part of the conversion.
+ */
+void drm_fb_xrgb8888_to_rgba5551(struct iosys_map *dst, const unsigned int *dst_pitch,
+				 const struct iosys_map *src, const struct drm_framebuffer *fb,
+				 const struct drm_rect *clip)
+{
+	static const u8 dst_pixsize[DRM_FORMAT_MAX_PLANES] = {
+		2,
+	};
+
+	drm_fb_xfrm(dst, dst_pitch, dst_pixsize, src, fb, clip, false,
+		    drm_fb_xrgb8888_to_rgba5551_line);
+}
+EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgba5551);
+
 static void drm_fb_xrgb8888_to_rgb888_line(void *dbuf, const void *sbuf, unsigned int pixels)
 {
 	u8 *dbuf8 = dbuf;
@@ -763,6 +918,15 @@ int drm_fb_blit(struct iosys_map *dst, const unsigned int *dst_pitch, uint32_t d
 		if (dst_format == DRM_FORMAT_RGB565) {
 			drm_fb_xrgb8888_to_rgb565(dst, dst_pitch, src, fb, clip, false);
 			return 0;
+		} else if (dst_format == DRM_FORMAT_XRGB1555) {
+			drm_fb_xrgb8888_to_xrgb1555(dst, dst_pitch, src, fb, clip);
+			return 0;
+		} else if (dst_format == DRM_FORMAT_ARGB1555) {
+			drm_fb_xrgb8888_to_argb1555(dst, dst_pitch, src, fb, clip);
+			return 0;
+		} else if (dst_format == DRM_FORMAT_RGBA5551) {
+			drm_fb_xrgb8888_to_rgba5551(dst, dst_pitch, src, fb, clip);
+			return 0;
 		} else if (dst_format == DRM_FORMAT_RGB888) {
 			drm_fb_xrgb8888_to_rgb888(dst, dst_pitch, src, fb, clip);
 			return 0;