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/linux/drivers/gpu/drm/i915/gt/ |
H A D | intel_gt_pm.c | diff 4243cd5388c82ae8942510f349b798c62f89825c Mon Apr 27 10:40:00 CEST 2020 Chris Wilson <chris@chris-wilson.co.uk> 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
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H A D | intel_lrc.c | diff 4243cd5388c82ae8942510f349b798c62f89825c Mon Apr 27 10:40:00 CEST 2020 Chris Wilson <chris@chris-wilson.co.uk> 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
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