Date:   Mon, 13 Nov 2017 21:00:02 +0000
From:   alexander.levin@...izon.com
To:     Tuncer Ayaz <tuncer.ayaz@...il.com>
CC:     "daniel.vetter@...el.com" <daniel.vetter@...el.com>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
        "seanpaul@...omium.org" <seanpaul@...omium.org>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: 4.1 EOL

I've cc'ed some folks in hopes to get this resolved upstream.

Either way, 4.1's EoL was previously moved to about 6 months from now,
so hopefully we'll have more than enough time to get this resolved.

On Sat, Nov 11, 2017 at 10:13:55PM +0000, Tuncer Ayaz wrote:
>The predicament I'm in on my machines is that ever since drm-intel has
>implemented atomic modesetting, there's a list regressions caused by
>those fundamental architecture changes and the code churn it implied.
>This means 4.1 is (from what I can tell) the last kernel before atomic
>modesetting was added and the only kernel free of all those issues
>which necessitate trying out various combinations of flags on the
>kernel cmdline.
>
>For instance, right now I'm trying 4.13.12 with these flags:
>video=SVIDEO-1:d
>i915.semaphores=1
>i915.enable_rc6=0
>i915.enable_psr=0
>intel_iommu=igfx_off
>
>PS: I'm kinda confused how anyone uses DMAR with VT-d when it's known
>to be buggy.
>
>The flags seem to decrease the chances of provoking the bugs, but after a
>day of running Xorg, it's possible to still hit the RCS0 GPU hangs.
>
>If you don't pass video=SVIDEO-1:d, then atomic's flip_done times out
>on boot or exit to VT console. It's good that other people have the same
>issues and have been following the bugzilla tickets, and con confirm
>the results.
>
>I'm kinda glad I don't have a machine that's newer than Sandybridge
>since that means I can use 4.1, though it's not a long-term solution,
>and the plan is for the reported bugzilla tickets to be resolved at
>some point, or me switching away from Intel GPUs, which might be
>doable if I save money and get an AMD APU laptop next summer and
>switch my desktop to a discrete GPU.
>
>For example:
>https://bugs.freedesktop.org/show_bug.cgi?id=101237
>https://bugs.freedesktop.org/show_bug.cgi?id=103076
>https://bbs.archlinux.org/viewtopic.php?id=218581&p=3
>https://bugs.archlinux.org/task/51703
>
>So, since 4.4, 4.9 and 4.12, drm-tip are still regressive,
>I wanted to ask if you considered pushing back 4.1's EOL.
>
>Given a look at bugzilla, I have the impression that those issues will
>need at least another year before they're fixed, since most of them
>have been sitting there for many, many months. I suspect the Intel DRM
>team doesn't have the bandwidth to address the issues in a timely
>fashion while still adding upbringing for new GPUs and features
>(fences, etc.).
>
>The generic modesetting DDX and Wayland are less susceptible to the
>GPU hangs, but can be made to provoke it if tried long enough.
>However, the modesetting DDX tears heavily and is about to gain atomic
>modesetting in the next Xorg release, so will suffer from the same
>easy GPU hang likelihood.
>
>Prior to SandyBridge there was zero tearing but beginning with
>SandyBridge xf86-video-intel's TearFree=TRUE is the only reliable way
>to fix Xorg tearing.
>
>I do appreciate you maintaining 4.1 so far and hate to admit that I'm
>reliant on it on more than two machines, before and after Sandybridge,
>exluding those machines which need a newer kernel. I also understand
>how much work this is and since I'm not using Linux professionally for
>a product, I can't offer compensation for your time. I can only offer
>to collect and point you at a list of DRM bugs for validation of my
>claims.

-- 

Thanks,
Sasha

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