Re: [PATCH 2/3] drm/i915/bxt: add revision id for A1 stepping and use it

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

On Wed, 07 Oct 2015, Jani Nikula <jani.nikula@intel.com> wrote:
> On Tue, 06 Oct 2015, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>> On Tue, Oct 06, 2015 at 04:43:11PM +0300, Jani Nikula wrote:
>>> On Tue, 06 Oct 2015, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
>>> > On Tue, Oct 06, 2015 at 02:41:15PM +0300, Jani Nikula wrote:
>>> >> Prefer inclusive ranges for revision checks rather than "below B0". Per
>>> >> specs A2 is not used, so revid <= A1 matches revid < B0.
>>> >
>>> > The w/a db would say UNTIL_B0 etc., so might be easier to check against
>>> > it if we keep to the same convention.
>>> 
>>> So I wanted to double check what the convention is. I picked
>>> WaRsDisableCoarsePowerGating.
>>> 
>>> KBL - SIWA_FOREVER
>>> BXT - SI_WA_BEFORE(BXT_REV_ID_B0)
>>> SKL - SIWA_UNTIL_SKL_E0
>>> 
>>> Description "Disable coarse power gating for GT4 until GT F0 stepping."
>>> 
>>> *rolls eyes*
>>> 
>>> So is that "until" there inclusive or non-inclusive? The db is
>>> contradicting itself...
>>
>> Hmm. My recollection was that it's exclusive, but now that I look at
>> your findings and some other workarounds, it does look a bit more like
>> inclusive.
>>
>> I would think the exclusive thing would be easier to maintain since
>> the hsd specifies the stepping in which stuff got fixed, and the
>> exclusive convention would then have the same stepping listed. Eg. if
>> the hsd says fixed in E0, but the w/a db says UNTIL_D0, then one is
>> left wondering about D1+ But perhaps such steppings didn't even exist.
>>
>> Well, in reality it's all over the place. Eg. looking at the BDW UNTIL_D0
>> stuff, some are fixed in E0, some are fixed in D0, and at least one was
>> fixed in B0 according to hsd. So I'm starting to think that the meaning
>> of the tag depends entirely on the person who pushed the change.
>
> With that, I stand by the patches I submitted as they are.

Ville, opinions, r-b, nak, ack, crap, what? ;)

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center
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