vgacon: prevent vgacon_deinit from touching the hardware for inactive consoles.

fbcon makes the (reasonable) assumption that it only needs to program the
hardware once, when fbcon_init() is called for the foreground console.

This doesn't always play well with vgacon because vgacon_deinit() is only
doing its job when the last console it owns is closed (when switching from
vgacon to fbcon, that's usually *after* fbcon_init() has set the new
mode).

Depending on the hardware this can cause the wrong framebuffer location to
be scanned out (e.g.  reproduced on nv05 with the nouveau framebuffer
driver).

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 74e96cf83b7e..da55ccaf4d55 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -589,12 +589,14 @@ static void vgacon_init(struct vc_data *c, int init)
 
 static void vgacon_deinit(struct vc_data *c)
 {
-        /* When closing the last console, reset video origin */
-        if (!--vgacon_uni_pagedir[1]) {
+        /* When closing the active console, reset video origin */
+        if (CON_IS_VISIBLE(c)) {
                 c->vc_visible_origin = vga_vram_base;
                 vga_set_mem_top(c);
-                con_free_unimap(c);
         }
+
+        if (!--vgacon_uni_pagedir[1])
+                con_free_unimap(c);
         c->vc_uni_pagedir_loc = &c->vc_uni_pagedir;
         con_set_default_unimap(c);
 }