** Description changed:
- CNL-Y SDP machine hangs soon after the system has booted up, and needs
- this from drm-intel-next-queued to fix it:
+ CNL-Y SDP machine hangs soon after logging in, and needs this from
+ intel-gfx list:
- commit 61bf9719fa170cd73b1937770d08cb062e070958
- Author: Mika Kuoppala <mika.kuopp...@linux.intel.com>
- Date: Thu Apr 12 17:58:02 2018 +0300
+ Author: Chris Wilson <ch...@chris-wilson.co.uk>
+ Date: Tue May 8 13:15:00 2018 +0300
- drm/i915/cnl: Use mmio access to context status buffer
+ drm/i915/execlists: Use rmb() to order CSB reads
- Evidence indicates that Cannonlake HWSP is not coherent
- as it should. Revert to using mmio access for now.
+ We assume that the CSB is written using the normal ringbuffer
+ coherency protocols, as outlined in kernel/events/ring_buffer.c:
- Testcase: igt/gem_ctx_switch
+ * (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
- Cc: Chris Wilson <ch...@chris-wilson.co.uk>
+ 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: Rodrigo Vivi <rodrigo.v...@intel.com>
- Signed-off-by: Mika Kuoppala <mika.kuopp...@linux.intel.com>
- Acked-by: Chris Wilson <ch...@chris-wilson.co.uk>
- Link:
https://patchwork.freedesktop.org/patch/msgid/20180412145802.23313-1-mika.kuopp...@linux.intel.com
+ Cc: Michel Thierry <michel.thie...@intel.com>
+ Cc: Timo Aaltonen <tjaal...@ubuntu.com>
+ Signed-off-by: Timo Aaltonen <timo.aalto...@canonical.com>
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-oem in Ubuntu.
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:
In Progress
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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