Re: [igt-dev] [PATCH i-g-t] tests/kms_dp_dsc: Force a full modeset when we force dsc enable

[Manasi Navare <manasi.d.navare@intel.com>]

On Thu, Apr 04, 2019 at 12:42:33AM +0300, Imre Deak wrote:
> On Wed, Apr 03, 2019 at 01:49:44PM -0700, Manasi Navare wrote:
> > [...]
> > Currently we have inh i915_dsc_fec_support_show:
> > DSC_enabled:
> > DSC_sink_support:
> > FEC_sink_support:
> 
> Yes, and after the kernel change you'll have an additional
>   
>   Force DSC enable: yes/no
> 
> line here.
> 
> > And this node we open as a read only first and then as write node and
> > force_dsc_enable() from IGT just writes a 1 to this, so you are saying
> > that in the kernel _write() node, I accept this and write to
> > force_dsc_enable entry in this file instead of rewriting the whole
> > file?
> 
> I'm not sure what you mean. Currently "1" or "0" is written to the
> debugfs file which will set intel_dp->force_dsc_enable. This doesn't
> need to be changed at all, no need to rewrite the whole file.
> 
> > So in IGT also I will have to parse the file and write 1 for
> > force_dsc_enable entry?
> 
> You can get the original value of it similarly to how it's done already
> for 'DSC_Sink_Support', by reading the file and doing
> 
> 	strstr(buf, "Force DSC enable: yes");
> 
> on the content.
> 
> > I still cant figure out how the restore() function work, we write the
> > stored_values and write for each of the entries in the file? And then
> > in the kernel debugfs_write, get these and write back to each entry?
> 
> Only force_dsc_enable need to be restored, the only value that you
> change by writing to the debugfs file. All the rest are calculated
> values that you don't need to care about.

But now that I rething then, force_dsc_enable is always 0, it s a variable
that we use to force DSC only if IGT asks to, so for test we force it to 1
and then after the test always clear it since the original value is always 0.
So why do we need a separate restore() for just force_dsc_enable if the value
is always 0.

Manasi

> 
> --Imre
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