[Intel-gfx] [PATCH] drm/i915: Delay disabling of VGA memory until vgacon->fbcon handoff is done

[Paulo Zanoni]

2013/9/6 Daniel Vetter <daniel at ffwll.ch>:
> On Thu, Sep 05, 2013 at 08:40:52PM +0300, ville.syrjala at linux.intel.com wrote:
>> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>
>> When transitioning away from vgacon the system tries to save the
>> current contents of the VGA memory, so that it can be cleanly handed
>> off to fbcon (or whatever comes afterwards).
>>
>> The recent change
>>
>>  commit 81b5c7bc8de3e6f63419139c2fc91bf81dea8a7d
>>  Author: Alex Williamson <alex.williamson at redhat.com>
>>  Date:   Wed Aug 28 09:39:08 2013 -0600
>>
>>     i915: Update VGA arbiter support for newer devices
>>
>> caused i915 to disable VGA memory decode for the IGD when i915 is
>> initializing. Unfortunately that happens before the vgacon->fbcon
>> handoff so vgacon_save_screen() will read out all ones from the
>> VGA memory.
>>
>> After the handoff fbcon will inherit the bogus state from vgacon,
>> and pre-fills the fb with matching contents. The end result is
>> a white rectangle in the top left corner of the screen, the size
>> of which matches the now inactive VGA console.
>>
>> To remedy the situation delay the disabling of VGA memory until
>> the vgacon->fbcon handoff has happened.
>>
>> Also rename i915_enable_vga to i915_enable_vga_mem to make
>> the relationship between these functions clearer.
>>
>> Cc: Alex Williamson <alex.williamson at redhat.com>
>> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Picked up for -fixes, thanks for the patch.

This patch causes "Unclaimed register" errors when you boot Haswell
with only an eDP output...


> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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-- 
Paulo Zanoni