[v2] drm/i915: Also perform gpu reset under execlist mode.

Commit Message

[e-mail] July 3, 2015, 4:27 p.m. UTC

From: "Niu,Bing" <[e-mail]>

It is found that i915 will not reset gpu under execlist mode when
unload module. that will lead to some issues when unload/load module
with different submission mode. e.g. from execlist mode to ring
buffer mode via loading/unloading i915. Because HW is not in a reset
state and registers are not clean under such condition.

Signed-off-by: Niu,Bing <[e-mail]>
---
 drivers/gpu/drm/i915/i915_gem.c |    8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Chris Wilson July 3, 2015, 9:01 a.m. UTC | #1

On Sat, Jul 04, 2015 at 12:27:34AM +0800, [e-mail] wrote:
> From: "Niu,Bing" <[e-mail]>
> 
> It is found that i915 will not reset gpu under execlist mode when
> unload module. that will lead to some issues when unload/load module
> with different submission mode. e.g. from execlist mode to ring
> buffer mode via loading/unloading i915. Because HW is not in a reset
> state and registers are not clean under such condition.
> 
> Signed-off-by: Niu,Bing <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>

I think we may end up doing the reset unconditionally in
i915_driver_unload() because this argument holds for almost everything
we setup. It's a bigger risk because of doing the gpu-reset on more
machines, but module-unloading is a "developer feature"!

The only issue is making sure that the reset is ordered appropriately.
-Chris

Mika Kuoppala July 3, 2015, 10:52 a.m. UTC | #2

Chris Wilson <[e-mail]> writes:

> On Sat, Jul 04, 2015 at 12:27:34AM +0800, [e-mail] wrote:
>> From: "Niu,Bing" <[e-mail]>
>> 
>> It is found that i915 will not reset gpu under execlist mode when
>> unload module. that will lead to some issues when unload/load module
>> with different submission mode. e.g. from execlist mode to ring
>> buffer mode via loading/unloading i915. Because HW is not in a reset
>> state and registers are not clean under such condition.
>> 
>> Signed-off-by: Niu,Bing <[e-mail]>
> Reviewed-by: Chris Wilson <[e-mail]>
>
> I think we may end up doing the reset unconditionally in
> i915_driver_unload() because this argument holds for almost everything
> we setup. It's a bigger risk because of doing the gpu-reset on more
> machines, but module-unloading is a "developer feature"!

And after that has been sorted, we should try reset on module load.

This way initial state would be identical to after reset/unload state.
Now we have this situation that we don't know how much we are leaning on
bios on state setup.

-Mika

> The only issue is making sure that the reset is ordered appropriately.
> -Chris
>
> -- 
> Chris Wilson, Intel Open Source Technology Centre
> _______________________________________________
> Intel-gfx mailing list
> [e-mail]
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Patch

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index be35f04..7855dd3 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5115,6 +5115,14 @@  i915_gem_cleanup_ringbuffer(struct drm_device *dev)
 
 	for_each_ring(ring, dev_priv, i)
 		dev_priv->gt.cleanup_ring(ring);
+
+    if (i915.enable_execlists)
+            /*
+             * Neither the BIOS, ourselves or any other kernel
+             * expects the system to be in execlists mode on startup,
+             * so we need to reset the GPU back to legacy mode.
+             */
+            intel_gpu_reset(dev);
 }
 
 static void