[Intel-gfx] [PATCH] drm/i915/vlv: Added/removed Render specific Hw Workarounds for VLV

[Goel, Akash]

>> Really? WaReadAfterWriteHazard in intel_ring_flush_all_caches() and WaTlbInvalidateStoreDataBefore in intel_ring_invalidate_all_caches()?
Sorry for this lapse, we have already identified this, will cover this change inside the VLV platform check.

>> My opinion still stands. I think all workarounds are fragile by definition, and should be separate patches.
Understood your concern, will split the work in multiple patches.

Best Regards
Akash
-----Original Message-----
From: Jani Nikula [mailto:jani.nikula at linux.intel.com] 
Sent: Monday, January 20, 2014 1:50 PM
To: Goel, Akash; intel-gfx at lists.freedesktop.org
Subject: RE: [Intel-gfx] [PATCH] drm/i915/vlv: Added/removed Render specific Hw Workarounds for VLV

On Sun, 19 Jan 2014, "Goel, Akash" <akash.goel at intel.com> wrote:
>>> Frankly, I don't know much about these particular workarounds, but 
>>> for bisecting any regressions it would probably be a good idea to 
>>> split the patch per workaround touched.

> Sorry for late response on this, actually we have done sufficient 
> testing for this patch.

I'm happy to hear that. However no reasonable amount of testing will cover the astonishing variety of conditions this code will run under out there in the real world, and if something blows up, we might never be able reproduce it ourselves.

> Moreover these workarounds are applicable to VLV only & will not 
> affect any other platforms.

Really? WaReadAfterWriteHazard in intel_ring_flush_all_caches() and WaTlbInvalidateStoreDataBefore in intel_ring_invalidate_all_caches()?

Btw our convention is to append the affected platforms to the w/a names in the code; please look around for examples.

> So probably it can be pushed as it is without splitting. 

My opinion still stands. I think all workarounds are fragile by definition, and should be separate patches.

Quoting Daniel, "if a regression would bisect to this, and the bisect is the only useful piece of evidence, would I stand a chance to understand it?"


BR,
Jani.


--
Jani Nikula, Intel Open Source Technology Center