From c9ffc5af56c0c808c0348e13ef04b9c5ff2cb69e Mon Sep 17 00:00:00 2001
From: Emil Velikov <emil.velikov@collabora.com>
Date: Fri, 4 Jun 2021 16:49:05 +0100
Subject: drm/i915: apply WaEnableVGAAccessThroughIOPort as needed
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Git-commit: a3af0140663dc335e5c18277a61bb99bfcb60694
Patch-mainline: v5.15-rc1
References: jsc#SLE-22601
Currently as the workaround is applied the screen flickers. As a result
we do not achieve seamless boot experience.
Avoiding the issue in the common use-case might be hard, although we can
resolve it for dual GPU setups - when the "other" GPU is primary and/or
outputs are connected to it.
With this I was able to get seamless experience on my Intel/Nvidia box,
running systemd-boot and sddm/Xorg. Note that the i915 driver is within
initrd while the Nvidia one is not.
Without this patch, the splash presented by systemd-boot (UEFI BGRT) is
torn down as the code-path kicks in, leaving the monitor blank until the
login manager starts.
Same issue were reported with plymouth/grub, although personally I
wasn't able to get them to behave on my setup.
Suggested-by: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210604154905.660142-1-emil.l.velikov@gmail.com
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/display/intel_vga.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_vga.c b/drivers/gpu/drm/i915/display/intel_vga.c
index f002b82ba9c0..3385b45ecd4b 100644
--- a/drivers/gpu/drm/i915/display/intel_vga.c
+++ b/drivers/gpu/drm/i915/display/intel_vga.c
@@ -29,6 +29,9 @@ void intel_vga_disable(struct drm_i915_private *dev_priv)
i915_reg_t vga_reg = intel_vga_cntrl_reg(dev_priv);
u8 sr1;
+ if (intel_de_read(dev_priv, vga_reg) & VGA_DISP_DISABLE)
+ return;
+
/* WaEnableVGAAccessThroughIOPort:ctg,elk,ilk,snb,ivb,vlv,hsw */
vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO);
outb(SR01, VGA_SR_INDEX);
--
2.33.1