[Intel-gfx] [PATCH 1/6] drm/i915/vlv: assert and de-assert sideband reset at boot and resume v3

[Daniel Vetter]

On Tue, May 27, 2014 at 10:32:47PM +0300, Ville Syrjälä wrote:
> On Fri, May 23, 2014 at 01:16:40PM -0700, Jesse Barnes wrote:
> > This is a bit like the CMN reset de-assert we do in DPIO_CTL, except
> > that it resets the whole common lane section of the PHY.  This is
> > required on machines where the BIOS doesn't do this for us on boot or
> > resume to properly re-calibrate and get the PHY ready to transmit data.
> > 
> > Without this patch, such machines won't resume correctly much of the time,
> > with the symptom being a 'port ready' timeout and/or a link training
> > failure.
> > 
> > Note that simply asserting reset at suspend and de-asserting at resume
> > is not sufficient, nor is simply de-asserting at boot.  Both of these
> > cases have been tested and have still been found to have failures on
> > some configurations.
> > 
> > v2: extract simpler set_power_well function for use in reset_dpio (Imre)
> >     move to reset_dpio (Daniel & Ville)
> > v3: don't reset if DPIO reset is already de-asserted (Imre)
> > 
> > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> 
> The series matches my understanding of the limitations of the PHY, so:
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

All merged to dinq, thanks.
 
> But if these limitations are real, then I think we would also need to
> adjust the power domains to power up all the wells whenever even a
> single one is required.
> 
> This should be testable I think by simply:
> 1. disable both ports
> 2. enable one port
> 3. enable the other port
> 
> At step 3. the common well is already up, so the TX wells for the second
> port should come up in some kind of poor state.

Hm, if we need this we might forc a modeset for _all_ pipes on vlv, even
for unchanged ports. At elast as long as we enable something new. That
should make this work properly I hope.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch