bcm27xx: add support for linux v5.15

Build system: x86_64
Build-tested: bcm2708, bcm2709, bcm2710, bcm2711
Run-tested: bcm2708/RPiB+, bcm2709/RPi3B, bcm2710/RPi3B, bcm2711/RPi4B

Signed-off-by: Marty Jones <mj8263788@gmail.com>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/target/linux/bcm27xx/patches-5.15/950-0004-drm-vc4-hdmi-Remove-the-DDC-probing-for-status-detec.patch b/target/linux/bcm27xx/patches-5.15/950-0004-drm-vc4-hdmi-Remove-the-DDC-probing-for-status-detec.patch
new file mode 100644
index 0000000000..f4dd7878d4
--- /dev/null
+++ b/target/linux/bcm27xx/patches-5.15/950-0004-drm-vc4-hdmi-Remove-the-DDC-probing-for-status-detec.patch
@@ -0,0 +1,47 @@
+From faa24f47c0066893e0b7772befe378bde4dc2ff9 Mon Sep 17 00:00:00 2001
+From: Maxime Ripard <maxime@cerno.tech>
+Date: Mon, 25 Oct 2021 17:28:54 +0200
+Subject: [PATCH] drm/vc4: hdmi: Remove the DDC probing for status
+ detection
+
+Commit 9d44abbbb8d5 ("drm/vc4: Fall back to using an EDID probe in the
+absence of a GPIO.") added some code to read the EDID through DDC in the
+HDMI driver detect hook since the Pi3 had no HPD GPIO back then.
+However, commit b1b8f45b3130 ("ARM: dts: bcm2837: Add missing GPIOs of
+Expander") changed that a couple of years later.
+
+This causes an issue though since some TV (like the LG 55C8) when it
+comes out of standy will deassert the HPD line, but the EDID will
+remain readable.
+
+It causes an issues nn platforms without an HPD GPIO, like the Pi4,
+where the DDC probing will be our primary mean to detect a display, and
+thus we will never detect the HPD pulse. This was fine before since the
+pulse was small enough that we would never detect it, and we also didn't
+have anything (like the scrambler) that needed to be set up in the
+display.
+
+However, now that we have both, the display during the HPD pulse will
+clear its scrambler status, and since we won't detect the
+disconnect/reconnect cycle we will never enable the scrambler back.
+
+As our main reason for that DDC probing is gone, let's just remove it.
+
+Signed-off-by: Maxime Ripard <maxime@cerno.tech>
+Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
+Link: https://lore.kernel.org/r/20211025152903.1088803-2-maxime@cerno.tech
+---
+ drivers/gpu/drm/vc4/vc4_hdmi.c | 2 --
+ 1 file changed, 2 deletions(-)
+
+--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
++++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
+@@ -175,8 +175,6 @@ vc4_hdmi_connector_detect(struct drm_con
+ 	if (vc4_hdmi->hpd_gpio &&
+ 	    gpiod_get_value_cansleep(vc4_hdmi->hpd_gpio)) {
+ 		connected = true;
+-	} else if (drm_probe_ddc(vc4_hdmi->ddc)) {
+-		connected = true;
+ 	} else if (HDMI_READ(HDMI_HOTPLUG) & VC4_HDMI_HOTPLUG_CONNECTED) {
+ 		connected = true;
+ 	}