Re: [PATCH 1/2] drm/i915: Add MOCS state dump to debugfs

[Stuart Summers <stuart.summers@intel.com>]

On Wed, 2019-08-07 at 22:29 +0100, Chris Wilson wrote:
> Quoting Stuart Summers (2019-08-07 21:55:55)
> > User applications might need to verify hardware configuration
> > of the MOCS entries. To facilitate this debug, add a new debugfs
> > entry to allow a dump of the MOCS state to verify expected values
> > are set by i915.
> 
> User applications + debugfs? It's not an avenue for ABI.
> 
> If you really want to provide the settings back to userspace, look at
> something like an i915_query or sysfs.
> 
> Or if you just mean igt, then add a Testcase:
> 
> If you just need to validate that we are setting and restoring them,
> selftests.
> 
> If you need them for debugging errors, add them to the error state.

This was probably poorly worded, you're right. I'll update the commit
message to be more specific.

I do want this for debugging, but not sure error state is the right
place. This is for debugging performance issues, so no specific
failures. If you feel sysfs or i915_query are more correct here, I can
look at adding this there instead. Is there a reason we don't want this
in debugfs specifically?

Thanks,
Stuart

> -Chris
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