[PATCH v2 1/1] SeaVGABios/cbvga: Fix bpp for coreboot framebuffer

[Matt DeVillier]

> From 3e41f058836cd920ab67463d361b11a11729b390 Mon Sep 17 00:00:00 2001

From: Matt DeVillier 
Date: Tue, 11 Sep 2018 16:54:53 -0500
Subject: [PATCH v2 1/1] SeaVGABios/cbvga: Fix bpp for coreboot framebuffer

Commit 4b42cc4 [SeaVGABios/cbvga: Advertise correct pixel format] neglected
to wrap the cbfb mask size components in GET_FARVAR(), which resulted in a
bogus value for bpp, breaking output on most/all devices.  Fix this by
adding GET_FARVAR() as appropriate.

Additionally, some newer ChromeOS devices still fail even with this fix,
so fall back to using the coreboot reported bit depth if the calculated
valid is invalid.

TEST: build/boot a variety of devices (google/[reef,eve], purism/librem_skl)
using coreboot framebuffer init, verify SeaBIOS boot menu prompt visible.

Signed-off-by: Matt DeVillier 
---
 vgasrc/cbvga.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/vgasrc/cbvga.c b/vgasrc/cbvga.c
index 859524c..438d8fd 100644
--- a/vgasrc/cbvga.c
+++ b/vgasrc/cbvga.c
@@ -312,11 +312,17 @@ cbvga_setup(void)
     }

u64 addr = GET_FARVAR(0, cbfb->physical_address);
-    u8 bpp = cbfb->blue_mask_size + cbfb->green_mask_size
-             + cbfb->red_mask_size + cbfb->reserved_mask_size;
+    u8 bpp = GET_FARVAR(0, cbfb->blue_mask_size)
+             + GET_FARVAR(0, cbfb->green_mask_size)
+             + GET_FARVAR(0, cbfb->red_mask_size)
+             + GET_FARVAR(0, cbfb->reserved_mask_size);
     u32 xlines = GET_FARVAR(0, cbfb->x_resolution);
     u32 ylines = GET_FARVAR(0, cbfb->y_resolution);
     u32 linelength = GET_FARVAR(0, cbfb->bytes_per_line);
+    //fall back to coreboot reported bpp if calculated value invalid
+    if (bpp != 15 && bpp != 16 && bpp != 24 && bpp != 32)
+        bpp = GET_FARVAR(0, cbfb->bits_per_pixel);
+
     dprintf(1, "Found FB @ %llx %dx%d with %d bpp (%d stride)\n"
             , addr, xlines, ylines, bpp, linelength);