target/linux/brcm2708/patches-4.19/950-0630-drm-vc4-A-present-but-empty-dmas-disables-audio.patch

   1 From 8befbf55f2668a4dae739588ed3c0b0d06fccacd Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Wed, 31 Jul 2019 17:36:34 +0100
   4 Subject: [PATCH] drm/vc4: A present but empty dmas disables audio
   5
   6 Overlays are unable to remove properties in the base DTB, but they
   7 can overwrite them. Allow a present but empty 'dmas' property
   8 to also disable the HDMI audio interface.
   9
  10 See: https://github.com/raspberrypi/linux/issues/2489
  11
  12 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  13 ---
  14  drivers/gpu/drm/vc4/vc4_hdmi.c | 6 ++++--
  15  1 file changed, 4 insertions(+), 2 deletions(-)
  16
  17 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
  18 +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
  19 @@ -1087,10 +1087,12 @@ static int vc4_hdmi_audio_init(struct vc
  20         struct device *dev = &hdmi->pdev->dev;
  21         const __be32 *addr;
  22         int ret;
  23 +       int len;
  24
  25 -       if (!of_find_property(dev->of_node, "dmas", NULL)) {
  26 +       if (!of_find_property(dev->of_node, "dmas", &len) ||
  27 +           len == 0) {
  28                 dev_warn(dev,
  29 -                        "'dmas' DT property is missing, no HDMI audio\n");
  30 +                        "'dmas' DT property is missing or empty, no HDMI audio\n");
  31                 return 0;
  32         }
  33