Re: [PATCH v3] drm/i915/fbc: FBC causes display flicker when VT-d is enabled on Skylake

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 23 Jun 2016, "Zanoni, Paulo R" <paulo.r.zanoni@intel.com> wrote:
> Em Ter, 2016-06-21 às 08:25 +0100, Chris Wilson escreveu:
>> Erratum SKL075: Display Flicker May Occur When Both VT-d And FBC Are
>> Enabled
>> 
>> "Display flickering may occur when both FBC (Frame Buffer
>> Compression)
>> and VT - d (Intel® Virtualization Technology for Directed I/O) are
>> enabled
>> and in use by the display controller."
>> 
>> Ville found the w/a name in the database:
>> WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl
>> 
>> v2: Log when the quirk is applied.
>> v3: Ensure i915.enable_fbc is false when !HAS_FBC()
>> 
>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/i915_drv.h  |  2 ++
>>  drivers/gpu/drm/i915/intel_fbc.c | 19 +++++++++++++++++++
>>  2 files changed, 21 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h
>> b/drivers/gpu/drm/i915/i915_drv.h
>> index 89298d3ad94b..f1e9fd07d441 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -2586,6 +2586,8 @@ struct drm_i915_cmd_table {
>>  #define INTEL_GEN(p)	(INTEL_INFO(p)->gen)
>>  #define INTEL_DEVID(p)	(INTEL_INFO(p)->device_id)
>>  
>> +#define mkwrite_intel_info(p) ((struct intel_device_info
>> *)INTEL_INFO(p))
>
> So why don't we un-const struct intel_device_info?

Yeah, this is more than a little ugly. Either it should stay const and
we shouldn't modify it (except in intel_device_info_runtime_init(), and
even that is a bit ugly), or we make it non-const.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center
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