From 6c8947a1a830e13a0dda9c149376c8731bdd29ac Mon Sep 17 00:00:00 2001 From: Sergei Antonov Date: Tue, 15 Apr 2014 23:18:37 +0200 Subject: [PATCH] drm/nouveau/bios: fix a bit shift error introduced by 6263c32 Commit 6263c32ea214779747d42cdcc71e198dea598e24 added two checks applied to a value received from nv_rd32(bios, 0x619f04). But after this new piece of code is executed, the addr local variable does not hold the same value it used to hold before the commit. Here is what is was assigned in the original code: (u64)(nv_rd32(bios, 0x619f04) & 0xffffff00) << 8 in the committed code it ends up with this value: (u64)(nv_rd32(bios, 0x619f04) >> 8) << 8 These expressions are obviously not equivalent. My Nvidia video card does not show anything on the display when I boot a kernel containing this commit. The patch fixes the code so that the new checks are still done, but the side effect of an incorrect addr value is gone. Cc: Ben Skeggs Cc: Dave Airlie Cc: Andrew Morton Signed-off-by: Sergei Antonov Signed-off-by: Dave Airlie --- drivers/gpu/drm/nouveau/core/subdev/bios/base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/nouveau/core/subdev/bios/base.c b/drivers/gpu/drm/nouveau/core/subdev/bios/base.c index e9df94f96d782..fb0b6b2d1427f 100644 --- a/drivers/gpu/drm/nouveau/core/subdev/bios/base.c +++ b/drivers/gpu/drm/nouveau/core/subdev/bios/base.c @@ -109,7 +109,7 @@ nouveau_bios_shadow_pramin(struct nouveau_bios *bios) return; } - addr = (u64)(addr >> 8) << 8; + addr = (addr & 0xffffff00) << 8; if (!addr) { addr = (u64)nv_rd32(bios, 0x001700) << 16; addr += 0xf0000; -- 2.39.5