[PATCH 12/18] drm/sysfb: ofdrm: Add EDID support

[Thomas Zimmermann <tzimmermann@suse.de>]

Add EDID support to sysfb connector helpers. Read the EDID property
from the OF node in ofdrm. Without EDID, this does nothing.

Some systems with OF display, such as 32-bit PPC Macintoshs, provide
the system display's EDID data as node property in their DT. Exporting
this information allows compositors to implement correct DPI and
meaningful color management.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/sysfb/drm_sysfb_helper.c | 29 ++++++++++++++++++++++++
 drivers/gpu/drm/sysfb/drm_sysfb_helper.h |  2 ++
 drivers/gpu/drm/sysfb/ofdrm.c            | 20 ++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/drivers/gpu/drm/sysfb/drm_sysfb_helper.c b/drivers/gpu/drm/sysfb/drm_sysfb_helper.c
index b48e06b25305..cb65c618f8d3 100644
--- a/drivers/gpu/drm/sysfb/drm_sysfb_helper.c
+++ b/drivers/gpu/drm/sysfb/drm_sysfb_helper.c
@@ -9,6 +9,7 @@
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_edid.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_atomic_helper.h>
@@ -281,10 +282,38 @@ EXPORT_SYMBOL(drm_sysfb_crtc_atomic_destroy_state);
  * Connector
  */
 
+static int drm_sysfb_get_edid_block(void *data, u8 *buf, unsigned int block, size_t len)
+{
+	const u8 *edid = data;
+	size_t off = block * EDID_LENGTH;
+	size_t end = off + len;
+
+	if (!edid)
+		return -1;
+	if (end > EDID_LENGTH)
+		return -1;
+	memcpy(buf, &edid[off], len);
+
+	return 0;
+}
+
 int drm_sysfb_connector_helper_get_modes(struct drm_connector *connector)
 {
 	struct drm_sysfb_device *sysfb = to_drm_sysfb_device(connector->dev);
+	const struct drm_edid *drm_edid;
+
+	if (sysfb->edid) {
+		drm_edid = drm_edid_read_custom(connector, drm_sysfb_get_edid_block,
+						(void *)sysfb->edid);
+		if (drm_edid) {
+			drm_edid_connector_update(connector, drm_edid);
+			drm_edid_free(drm_edid);
+		} else {
+			drm_edid_connector_update(connector, NULL);
+		}
+	}
 
+	/* Return the fixed mode even with EDID */
 	return drm_connector_helper_get_modes_fixed(connector, &sysfb->fb_mode);
 }
 EXPORT_SYMBOL(drm_sysfb_connector_helper_get_modes);
diff --git a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
index 45e396bf74b7..3684bd0ef085 100644
--- a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
+++ b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
@@ -24,6 +24,8 @@ struct drm_display_mode drm_sysfb_mode(unsigned int width,
 struct drm_sysfb_device {
 	struct drm_device dev;
 
+	const u8 *edid; /* can be NULL */
+
 	/* hardware settings */
 	struct drm_display_mode fb_mode;
 	const struct drm_format_info *fb_format;
diff --git a/drivers/gpu/drm/sysfb/ofdrm.c b/drivers/gpu/drm/sysfb/ofdrm.c
index 71e661ba9329..86c1a0c80ceb 100644
--- a/drivers/gpu/drm/sysfb/ofdrm.c
+++ b/drivers/gpu/drm/sysfb/ofdrm.c
@@ -12,6 +12,7 @@
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_edid.h>
 #include <drm/drm_fbdev_shmem.h>
 #include <drm/drm_format_helper.h>
 #include <drm/drm_framebuffer.h>
@@ -227,6 +228,16 @@ static u64 display_get_address_of(struct drm_device *dev, struct device_node *of
 	return address;
 }
 
+static const u8 *display_get_edid_of(struct drm_device *dev, struct device_node *of_node,
+				     u8 buf[EDID_LENGTH])
+{
+	int ret = of_property_read_u8_array(of_node, "EDID", buf, EDID_LENGTH);
+
+	if (ret)
+		return NULL;
+	return buf;
+}
+
 static bool is_avivo(u32 vendor, u32 device)
 {
 	/* This will match most R5xx */
@@ -298,6 +309,8 @@ struct ofdrm_device {
 	/* colormap */
 	void __iomem *cmap_base;
 
+	u8 edid[EDID_LENGTH];
+
 	/* modesetting */
 	u32 formats[DRM_SYSFB_PLANE_NFORMATS(1)];
 	struct drm_plane primary_plane;
@@ -840,6 +853,7 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 	int width, height, depth, linebytes;
 	const struct drm_format_info *format;
 	u64 address;
+	const u8 *edid;
 	resource_size_t fb_size, fb_base, fb_pgbase, fb_pgsize;
 	struct resource *res, *mem;
 	void __iomem *screen_base;
@@ -989,6 +1003,9 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 		}
 	}
 
+	/* EDID is optional */
+	edid = display_get_edid_of(dev, of_node, odev->edid);
+
 	/*
 	 * Firmware framebuffer
 	 */
@@ -999,6 +1016,7 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 	sysfb->fb_pitch = linebytes;
 	if (odev->cmap_base)
 		sysfb->fb_gamma_lut_size = OFDRM_GAMMA_LUT_SIZE;
+	sysfb->edid = edid;
 
 	drm_dbg(dev, "display mode={" DRM_MODE_FMT "}\n", DRM_MODE_ARG(&sysfb->fb_mode));
 	drm_dbg(dev, "framebuffer format=%p4cc, size=%dx%d, linebytes=%d byte\n",
@@ -1072,6 +1090,8 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 	drm_connector_set_panel_orientation_with_quirk(connector,
 						       DRM_MODE_PANEL_ORIENTATION_UNKNOWN,
 						       width, height);
+	if (edid)
+		drm_connector_attach_edid_property(connector);
 
 	ret = drm_connector_attach_encoder(connector, encoder);
 	if (ret)
-- 
2.48.1