Commit 3800cd19 authored by Chris Wilson's avatar Chris Wilson

drm/i915/execlists: Stop storing the CSB read pointer in the mmio register

As we now never read back our current head position from the CSB
pointers register, and the HW itself doesn't use it to prevent
overwriting unread CSB entries, we do not need to keep updating the
register. As it turns out this register is not listed as being shadowed,
and so requires forcewake -- but we haven't been taking forcewake around
it so the writes has probably been regularly dropped. Fortuitously, we
only read the value after a reset where it did not matter, and zero was
the right answer (well, close enough).

Mika pointed out that this was how we used to do it (accidentally!)
before he fixed it in commit cc53699b ("drm/i915: Use masked write
for Context Status Buffer Pointer").

References: cc53699b ("drm/i915: Use masked write for Context Status Buffer Pointer")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180628201211.13837-7-chris@chris-wilson.co.uk
parent f4b58f04
...@@ -1118,8 +1118,6 @@ static void process_csb(struct intel_engine_cs *engine) ...@@ -1118,8 +1118,6 @@ static void process_csb(struct intel_engine_cs *engine)
} }
} while (head != tail); } while (head != tail);
writel(_MASKED_FIELD(GEN8_CSB_READ_PTR_MASK, head << 8),
execlists->csb_read);
execlists->csb_head = head; execlists->csb_head = head;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment