[PATCH 04/11] video: display: Skip modes which do not fit in the source frame buffer

[Ana Bobillo <anabobillo3@gmail.com>]

From: Ana Bobillo <anabobillo3@gmail.com>

display_read_timing() picks the first EDID timing which the display
driver accepts, but the display driver does not know how much memory
the video device feeding it has reserved for its frame buffer, so it
can pick a mode which does not fit.

Add the size and depth of the source's frame buffer to struct
display_plat, which the video device sets, as it does src_dev, before
it reads the timing. display_mode_valid() then skips the modes which do
not fit, so that a smaller one is picked. A video device which does not
set them is not affected.

Signed-off-by: Ana Bobillo <anabobillo3@gmail.com>
---
 drivers/video/display-uclass.c | 10 ++++++++++
 include/display.h              |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/drivers/video/display-uclass.c b/drivers/video/display-uclass.c
index 85dac12a197..06888df4112 100644
--- a/drivers/video/display-uclass.c
+++ b/drivers/video/display-uclass.c
@@ -42,6 +42,16 @@ static bool display_mode_valid(void *priv, const struct display_timing *timing)
 {
 	struct udevice *dev = priv;
 	struct dm_display_ops *ops = display_get_ops(dev);
+	struct display_plat *disp_uc_plat = dev_get_uclass_plat(dev);
+	u64 bits;
+
+	/* Skip modes which do not fit in the source's frame buffer */
+	if (disp_uc_plat->fb_size) {
+		bits = (u64)timing->hactive.typ * timing->vactive.typ *
+		       disp_uc_plat->fb_bpp;
+		if (bits > (u64)disp_uc_plat->fb_size * 8)
+			return false;
+	}
 
 	if (ops && ops->mode_valid)
 		return ops->mode_valid(dev, timing);
diff --git a/include/display.h b/include/display.h
index 26b965daba9..f2ff9ffced8 100644
--- a/include/display.h
+++ b/include/display.h
@@ -18,11 +18,17 @@ struct display_timing;
  * controller
  * @src_dev:	Source device providing the video
  * @in_use:	Display is being used
+ * @fb_size:	Size of the source's frame buffer in bytes, or 0 if unknown. Set
+ *		by the source before reading the timing, so that modes which
+ *		do not fit in the frame buffer are skipped
+ * @fb_bpp:	Bits per pixel of the source's frame buffer
  */
 struct display_plat {
 	int source_id;
 	struct udevice *src_dev;
 	bool in_use;
+	uint fb_size;
+	int fb_bpp;
 };
 
 /**