Re: [PATCH 10/12] drm/i915: Update link training automated test function for Displayport compliance

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Tue, 22 Jul 2014 08:15:30 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Mon, Jul 14, 2014 at 12:10:45PM -0700, Todd Previte wrote:
> > Implements basic link training functionality for Displayport automated compliance
> > testing.
> > 
> > Signed-off-by: Todd Previte <tprevite@gmail.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 47 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 65830e9..e4b31ad 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3427,6 +3427,53 @@ static uint8_t
> >  intel_dp_autotest_link_training(struct intel_dp *intel_dp)
> >  {
> >  	uint8_t test_result = DP_TEST_NAK;
> > +	uint8_t rxdata[2];
> > +	uint8_t link_status[DP_LINK_STATUS_SIZE];
> > +	int bytes_ret = 0;
> > +	struct drm_connector *connector = &intel_dp->attached_connector->base;
> > +	struct intel_digital_port *intel_dig_port =
> > +		enc_to_dig_port(&intel_dp->attached_connector->encoder->base);
> > +
> > +	/* Read test parameters */
> > +	bytes_ret = drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_LINK_RATE, rxdata, 2);
> > +
> > +	/* Set link rate directly */
> > +	intel_dp->link_bw = rxdata[0];
> > +	/* Preserve 7:5 when setting lane count */
> > +	intel_dp->lane_count &= 0xE0;
> > +	intel_dp->lane_count |= rxdata[1];
> 
> This won't work - if you change the link config you need to do a full
> recomputation of the modeset config and a full modeset. No, we dont (yet)
> have the infrastructure for this, which is why dp is such a pain since we
> can change the link config once we've decided on something :(

I think that depends on how we're going to structure the code.  For
simply calling the link train functions, it looks like messing with the
intel_dp->foo fields will roughly do what Todd wants, which is to
simply try a re-train with a different set of params, ignoring the
actual fb and pipe configuration.

Or is that what you had in mind?  You'd like to see valid data and mode
timings to drive a given lane count and bw instead?  I'm not sure the
testing spec cares about that; Todd?

-- 
Jesse Barnes, Intel Open Source Technology Center