On 31/05/17 17:45, Martin Peres wrote:
On 31/05/17 16:55, Chris Wilson wrote:
On Wed, May 31, 2017 at 04:44:41PM +0300, Martin Peres wrote:
On 31/05/17 15:42, Chris Wilson wrote:
On Wed, May 31, 2017 at 01:40:00PM +0300, Martin Peres wrote:
On 26/05/17 14:48, Chris Wilson wrote:
If we do a shallow probe of the connector and it reports the link
failed
previous (link-status != GOOD), force a full probe of the
connector to
give the kernel a chance to validate the mode list.
Sounds good, but will this make the tests SKIP if no modes are
available?
I'm actually not sure what will happen if the mode is removed. I think
the tests are just using the first mode in the list? At the moment I
hope just to stop turning a single failure into many, it is still a bug
that the link training failed and was not recovered. Alternatively, we
can ask why isn't the kernel taking the corrective action when
presented
with a new setcrtc?
No, this is not a kernel bug, it is a failure that the userspace has
to handle because the kernel can't do shit about this.
Have you demonstrated that the kernel is beyond reproach when it failed
the link training? Nothing changed in the connection and it works most
of the time, so why did the kernel accept the failure. Even if we
temporarily force a change of modes that is poor UX that I see no reason
why it should not have been prevented in the first place.
Sorry, this is not what I meant. What I meant is that the kernel is
allowed to have this behaviour.
I agree though that in the case of the skl bug, it is quite likely that
the kernel is doing something dodgy, but this is another bug. IGT should
learn to cope with modes disappearing.
I'm not sure what the correct approach here should be, just what is the
contract the kernel is expecting of userspace? Should that contract
apply to new clients unaware of the earlier error?
Right, IGT assumes that if a mode is already set, it can be set
again. However, this assumption has been broken when the link-status
patches landed.
On a hotplug event, IGT should do a full reprobe, select one mode
from the list and use it. If no modes can be set and the test is
trying to set one, then the test should just SKIP.
There is no hotplug event when a new client starts so how is igt meant
to even know that it was supposed to pick up the pieces for the kernel.
Yes.
How about this: When the modeset call fails, check if the link-status is
BAD. If not, return a FAIL. If so, force a full re-probe, pick the
highest available mode and try again. Do this until a mode applies. If
no modes are left, just SKIP the test altogether.
Does this sound reasonable?
Martin
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