Re: [PATCH] drm/i915/kbl: Adding missing IS_KABYLAKE checks.

From: Daniel Vetter <daniel@ffwll.ch>
To: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	"Vivi, Rodrigo" <rodrigo.vivi@intel.com>
Subject: Re: [PATCH] drm/i915/kbl: Adding missing IS_KABYLAKE checks.
Date: Wed, 16 Mar 2016 16:32:55 +0100	[thread overview]
Message-ID: <20160316153255.GS14170@phenom.ffwll.local> (raw)
In-Reply-To: <871t7a8ndy.fsf@intel.com>

On Wed, Mar 16, 2016 at 05:15:37PM +0200, Jani Nikula wrote:
> On Wed, 16 Mar 2016, Michel Thierry <michel.thierry@intel.com> wrote:
> > [ text/plain ]
> > On 2/29/2016 2:35 PM, Jani Nikula wrote:
> >> On Fri, 26 Feb 2016, Rodrigo Vivi <rodrigo.vivi@gmail.com> wrote:
> >>> Hi Jani and Daniel,
> >>>
> >>> I believe I forgot to cc:stable on this one and this is missing on
> >>> most branches out there including Linus 4.5-r5.
> >>> Is there any chance to get this patch in for 4.5? without this i915 is
> >>> not working on KBL.
> >>
> >> Is the referenced commit by Michel also required?
> >>
> >>      Michel had found the main error first and his
> >>      fix had better details on the history and got
> >>      merged already:
> >>
> >>      commit 16fbc291cb87c7defcd13ad715d3e4af0d523e43
> >>      Author: Michel Thierry <michel.thierry@intel.com>
> >>      Date:   Wed Jan 6 12:08:36 2016 +0000
> >>
> >>          drm/i915/kbl: Enable PW1 and Misc I/O power wells
> >>
> >> If that's needed, what else is needed? Where does the rabbit hole end?
> >>
> >>> Good thing is that this platform is still protected by preliminary_hw_support.
> >>
> >> We do not backport cc: stable fixes for platforms that only have
> >> preliminary hw support.
> >>
> >> v4.5 is not released yet, and although towards the later -rc's the rules
> >> are pretty much the same as for stable kernels, I might consider
> >> cherry-picking kbl fixes that make platform enabling or early adoption
> >> easier.
> >>
> >
> > Hi Jani,
> >
> > Now that v4.5 has been released, would you consider _backporting_ these 
> > two patches to allow kbl to boot?
> 
> As I said we do not backport cc: stable fixes for platforms that only
> have preliminary hw support. We can discuss the rules we make for
> ourselves, but that discussion shouldn't be linked to specific patches.
> 
> So I might have cherry-picked them through fixes *before* v4.5 was
> released, but there was no response to my mail... communication fail
> from my part I guess, but I kind of expected opinions. "I might
> consider" does not mean "I am going to".
> 
> (Technically, *I* don't do stable backports. Also, the commits have to
> be in Linus' tree before they can be backported to stable. See
> Documentation/stable_kernel_rules.txt.)

Yup, backproting platform support when upstream isn't yet out of
prelim_hw_support or to kernels where that is still set doesn't make
sense. If you need platform support earlier, you need to make it clear
that we need to clear that milestone earlier. prelim_hw_support taints
your kernel for a reason.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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