Re: [PATCH 6/7] drm/i915: Restart RPS using the same RP_CONTROL as from initialisation

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> On Mon, Feb 20, 2017 at 04:40:47PM +0200, Mika Kuoppala wrote:
>> Chris Wilson <chris@chris-wilson.co.uk> writes:
>> 
>> > During initialisation, we set different flags for different
>> > architectures - these should be preserved when we reload the RPS
>> > thresholds. If we use a mmio read, it will first ensure that the
>> > threshold registers are written before we apply the latch in RP_CONTROL.
>> >
>> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>> > Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>> > Cc: stable@vger.kernel.org
>> 
>> This will change how the valleyview will do the DOWN_IDLE,
>> due to readback you will get a GEN6_RP_DOWN_IDLE_CONT.
>
> No change, since we don't use it on byt - we only use the EI intervals
> as we manually calculate the up/down signals based on the C0 counters.
>  
>> I can't think of why we would like to keep that behaviour
>> as the IDLE_CONT setup is a twart in my opinion.
>> 
>> If you agree with the above, substitute the IDLE_CONT in
>> valleview setup and you can add,
>
> It is a mistake in the setup, but that change has to be seperate to
> exclude it as being part of the magic that avoids the hang.

Ok, so let me rephrase. As the skipping of the IDLE_CONT had
an effect to the way byt behaves, we intentionally want to keep that
with byt.

So this is no accident, and yes it makes sense

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>


> -Chris
>
> -- 
> Chris Wilson, Intel Open Source Technology Centre