[Bug 110799] New: No Screen Updates on fbcon with PSR enabled on Thinkpad T450s (Broadwell), Linux 5.1.5

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110799

            Bug ID: 110799
           Summary: No Screen Updates on fbcon with PSR enabled on
                    Thinkpad T450s (Broadwell), Linux 5.1.5
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: trohwer85 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

I enabled PSR on my Thinkpad T450s (Broadwell) with Linux 5.1.5. This works
fine under X, but I get no screen updates on the fbcon (typing etc. does show
no change on screen, only switching to/back X makes the stuff visible).
Without PSR, the fbcon works fine.

I investigated a bit and identified this code in drm/i915/intel_psr.c
(printk added by me) to exit PSR on fbcon dirty calls:

  /* By definition flush = invalidate + flush */
  if (frontbuffer_bits) {
    /*
     * Display WA #0884: all
     * This documented WA for bxt can be safely applied
     * broadly so we can force HW tracking to exit PSR
     * instead of disabling and re-enabling.
     * Workaround tells us to write 0 to CUR_SURFLIVE_A,
     * but it makes more sense write to the current active
     * pipe.
     */
    printk(KERN_DEBUG "WA\n");
    I915_WRITE(CURSURFLIVE(dev_priv->psr.pipe), 0);
  }

The code is called for fbcon changes, but as stated, it does not seem to have
the effect of exiting PSR on my hardware.

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