drm/i915/gt: Sanitize GT first

We see that if the HW doesn't actually sleep, the HW may eat the poison
we set in its write-only HWSP during sanitize:

  intel_gt_resume.part.8: 0000:00:02.0
  __gt_unpark: 0000:00:02.0
  gt_sanitize: 0000:00:02.0 force:yes
  process_csb: 0000:00:02.0 vcs0: cs-irq head=5, tail=90
  process_csb: 0000:00:02.0 vcs0: csb[0]: status=0x5a5a5a5a:0x5a5a5a5a
  assert_pending_valid: Nothing pending for promotion!

The CS TAIL pointer should have been reset by reset_csb_pointers(), so
in this case it is likely that we have read back from the CPU cache and
so we must clflush our control over that page. In doing so, push the
sanitisation to the start of the GT sequence so that our poisoning is
assuredly before we start talking to the HW.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/1794
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200427084000.10999-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
index 4c4c74ef4f213820b5158d7d5ffdb1a5f418db5b..5097786f43759dad770f194fb863737c2b2ad529 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
@@ -198,11 +198,12 @@ int intel_gt_resume(struct intel_gt *gt)
         * Only the kernel contexts should remain pinned over suspend,
         * allowing us to fixup the user contexts on their first pin.
         */
+       gt_sanitize(gt, true);
+
        intel_gt_pm_get(gt);
 
        intel_uncore_forcewake_get(gt->uncore, FORCEWAKE_ALL);
        intel_rc6_sanitize(&gt->rc6);
-       gt_sanitize(gt, true);
        if (intel_gt_is_wedged(gt)) {
                err = -EIO;
                goto out_fw;

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index cbd04b74ae2ac2a23894601d60788ba00a874004..93a1b73ad96b7036c9d843420a6b1d2cfb7e1798 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -3931,6 +3931,9 @@ static void execlists_sanitize(struct intel_engine_cs *engine)
         * reset the value in the HWSP.
         */
        intel_timeline_reset_seqno(engine->kernel_context->timeline);
+
+       /* And scrub the dirty cachelines for the HWSP */
+       clflush_cache_range(engine->status_page.addr, PAGE_SIZE);
 }
 
 static void enable_error_interrupt(struct intel_engine_cs *engine)