From d18fe1c54c9100e4e854fa1cec3f296e61d5f24d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Revol?= <revol@free.fr>
Date: Thu, 21 Feb 2019 05:11:00 +0100
Subject: [PATCH] loader: disable scaling on nvidia VESA BIOS

cf. https://patchwork.kernel.org/patch/7113461/

Change-Id: I3f564bd1037aeb4b539f495d57397446ae14e5ed
---
 src/system/boot/platform/bios_ia32/video.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/system/boot/platform/bios_ia32/video.cpp b/src/system/boot/platform/bios_ia32/video.cpp
index fa9b1fba8c..4a719478f7 100644
--- a/src/system/boot/platform/bios_ia32/video.cpp
+++ b/src/system/boot/platform/bios_ia32/video.cpp
@@ -439,12 +439,30 @@ vesa_get_vbe_info_block(vbe_info_block *info)
 }
 
 
+static void
+vesa_fixups(vbe_info_block *info)
+{
+	const char *oem_string = (const char *)info->oem_string;
+
+	if (!strcmp(oem_string, "NVIDIA")) {
+		dprintf("Disabling nvidia scaling.\n");
+		struct bios_regs regs;
+		regs.eax = 0x4f14;
+		regs.ebx = 0x0102;
+		regs.ecx = 1;	// centered unscaled
+		call_bios(0x10, &regs);
+	}
+}
+
+
 static status_t
 vesa_init(vbe_info_block *info, video_mode **_standardMode)
 {
 	if (vesa_get_vbe_info_block(info) != B_OK)
 		return B_ERROR;
 
+	vesa_fixups(info);
+
 	// fill mode list and find standard video mode
 
 	video_mode *standardMode = NULL;