Re: [PATCH v3 2/2] drm/i915/gtt: Avoid using addresses in non-canonical form.

Daniel Vetter
2015-09-23T12:28:36Z

On Thu, Sep 17, 2015 at 05:17:24PM +0000, Winiarski, Michal wrote:
> On śro, 2015-09-16 at 11:50 +0200, Michał Winiarski wrote:
> > According to bspec, some parts of HW expect the addresses to be in
> > a canonical form where bits [63:48] == [47].
> > If we're using 32b addressing, we never need to handle such high
> > addresses, but since we've recently added 48b address space support,
> > lets satisfy the HW by converting the address prior to
> > alloc/insert/clear.
> >
> > v2: Commit msg update,
> > move WARN to gen8_alloc_va_range,
> > also convert to canonical in insert_entries.
> > v3: Also convert for !48b (causes no harm, improves code stucture),
> > update wrap comment.
> >
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Michel Thierry <michel.thierry@intel.com>
> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> > Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
>
> Actually... Please ignore this patch.
> It's harmless, unfortunately it's also useless, and I need to address
> this in a different way.

Please explain in more detail why this patch is void - it seems to do
exactly what it says on the tin?

> Sorry for the noise.

Explaining why something doesn't work or not is never noise, but a great
opportunity to learn something.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation