** Changed in: linux-oem (Ubuntu Bionic)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1769843
Title:
[i915 CNL-Y] system hangs soon after bootup
Status in linux-oem package in Ubuntu:
Invalid
Status in linux-oem source package in Bionic:
Fix Committed
Bug description:
CNL-Y SDP machine hangs soon after logging in, and needs this from
intel-gfx list:
Author: Chris Wilson <ch...@chris-wilson.co.uk>
Date: Tue May 8 13:15:00 2018 +0300
drm/i915/execlists: Use rmb() to order CSB reads
We assume that the CSB is written using the normal ringbuffer
coherency protocols, as outlined in kernel/events/ring_buffer.c:
* (HW) (DRIVER)
*
* if (LOAD ->data_tail) { LOAD ->data_head
* (A) smp_rmb() (C)
* STORE $data LOAD $data
* smp_wmb() (B) smp_mb() (D)
* STORE ->data_head STORE ->data_tail
* }
So we assume that the HW fulfils it's ordering requirements, and so we
should use a complimentary rmb() to ensure that our read of its WRITE
pointer is completed before we start accessing the data.
The final mb() is implied by the uncached mmio we perform to inform the
HW of our READ pointer.
References: https://bugs.freedesktop.org/show_bug.cgi?id=105064
References: https://bugs.freedesktop.org/show_bug.cgi?id=105888
References: https://bugs.freedesktop.org/show_bug.cgi?id=106185
References: 61bf9719fa17 ("drm/i915/cnl: Use mmio access to context
status buffer")
Suggested-by: Mika Kuoppala <mika.kuopp...@linux.intel.com>
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuopp...@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Michał Winiarski <michal.winiar...@intel.com>
Cc: Rafael Antognolli <rafael.antogno...@intel.com>
Cc: Michel Thierry <michel.thie...@intel.com>
Cc: Timo Aaltonen <tjaal...@ubuntu.com>
Signed-off-by: Timo Aaltonen <timo.aalto...@canonical.com>
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