Re: drm/i915 4.5/4.6 stable backport request for CHV

[Greg KH <greg@kroah.com>]

On Fri, May 27, 2016 at 11:30:30AM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Several nasty i915 regressions affecting CHV slipped through
> to 4.5 and 4.6.
> 
> The first fix we want in 4.5 and 4.6 is
> commit caed361d83b2 ("drm/i915: Fix watermarks for VLV/CHV")
> It won't cherry-pick cleanly to either one, so I've included conflict
> free versions for both. This one fixes display FIFO underruns that can
> lead to the screen totally blanking out.

Now applied, thanks.

> The other one I'd like to have in 4.6 is
> commit 9f6151c90390 ("drm/i915: Pass the correct crtc state to .update_plane()")
> which avoids a totally corrupted display in some cases.

Now applied.

> And the third on is a bit more annoying. The regression is caused by
> commit 9dbaab56ac09 ("drm/i915: Exit cherryview_irq_handler() after one pass")
> which I though we had prevented from getting out on its own, but turns
> out I was wrong. It basically makes the GPU unusable, so we do need to
> fix it somehow. The simple solution would be to revert it in 4.6 only.
> The more complicated solution is to backport the proper fix, which more
> or less requires the following set of commits [1], which is maybe a bit
> too much for stable. I could try to trim it a bit perhaps, but then we
> start to enter the territory of untested code which I don't particularly
> like. Let me know what you think.
> 
> [1]
>  1e1cace942ef ("drm/i915: Eliminate loop from VLV irq handler")
>  a5e485a95c9c ("drm/i915: Clear VLV_IER around irq processing")
>  4a0a0202b023 ("drm/i915: Clear VLV_MASTER_IER around irq processing")
>  7ce4d1f2730f ("drm/i915: Clear VLV_IIR after PIPESTAT")
>  34c7b8a7b8b5 ("drm/i915: Set up VLV_MASTER_IER consistently")
>  e5328c43d46e ("drm/i915: Use GEN8_MASTER_IRQ_CONTROL consistently")
>  71b8b41d5b35 ("drm/i915: Move DPINVGTT setup to vlv_display_irq_reset()")
>  6b7eafc1b43d ("drm/i915: Warn if irq_mask isn't ~0 during vlv/cvh display irq postinstall")
>  9ab981f22bef ("drm/i915: Use GEN5_IRQ_INIT() in vlv_display_irq_postinstall()")
>  d6c698035892 ("drm/i915: Clear display interrupt before enabling when turning on the power well")
>  8bb613068a63 ("drm/i915: Move vlv/chv display irq code to a more logical place")
>  9918271efc7a ("drm/i915: Skip display irq setup if display irqs aren't flagged as enabled")
>  ad22d10654ea ("drm/i915: Fix up vlv/chv display irq setup")
>  93de68f94081 ("drm/i915: Remove "VLV magic" from irq setup")

I think reverting that one patch for 4.6 makes more sense than adding
all of these patches.  I'll do that if you want me to.

thanks,

greg k-h