[Intel-gfx] [PATCH] drm/i915/guc: Don't read SOFT_SCRATCH(15) on MMIO error

[Michal Wajdeczko]

On Tue, 29 May 2018 16:54:12 +0200, Chris Wilson  
<chris at chris-wilson.co.uk> wrote:

> Quoting Michal Wajdeczko (2018-05-28 18:16:18)
>> SOFT_SCRATCH(15) is used by GuC for sending MMIO GuC events to host and
>> those events are now handled by intel_guc_to_host_event_handler_mmio().
>>
>> We should not try to read it on MMIO action error as 1) we may be using
>> different set of registers for GuC MMIO communication, and 2) GuC may
>> use CTB mechanism for sending events to host.
>
> Ok.
>
>> While here, upgrade error message to DRM_ERROR.
>
> Does the error help? What do you want to convey to the user? For error
> handling, we want to propagate the result back anyway for the caller has
> to decide what to do next.

We are propagating error code to the caller, but since any error from the
GuC is unexpected, we should rather always log it and don't rely on the
caller or drm debug for that. Note that in case of CTB we also log received
errors using DRM_ERROR (see intel_guc_send_ct).

Michal