[Intel-gfx] [PATCH v2] drm/i915: State readout and cross-checking for dp_m2_n2

[Daniel Vetter]

On Mon, May 19, 2014 at 05:00:14PM +0530, Vandana Kannan wrote:
> Please let me know your inputs on this..
> Given that making changes to avoid DRRS related checks in
> pipe_config_compare affects the overall design and future
> implementations related to RR switching, I think that using a quirk for
> downclock_mode to compare dp_m_n and dp_m2_n2 based on the RR in use,
> 
> if (!low RR)
> 	compare dp_m_n
> else
> 	compare dp_m2_n2
> 
> would avoid unrelated DRRS checks and make sure extension of DRRS
> implementation would be possible.
> Only thing would be that both dp_m_n and dp_m2_n2 cant be compared always..

Well my idea was for bdw we'd check that

hw.dp_m_n == sw.dp_m_n || hw.dp_m_n == sw.dp_m2_n2

without any checks using software state to figure out whether we're in low
RR mode or not. That way the pipe config checker only depends upon the 2
pipe configs, which is a nice proper for it to have.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch