On Mon, Mar 27, 2017 at 09:53:36AM -0700, Manasi Navare wrote:
> On Mon, Mar 27, 2017 at 06:26:06PM +0300, Jani Nikula wrote:
> > On Mon, 27 Mar 2017, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> > > On Thu, Mar 23, 2017 at 04:11:32PM -0700, Manasi Navare wrote:
> > >> Currently intel_dp_check_link_status() tries to retrain the link if
> > >> Clock recovery or Channel EQ for any of the lanes indicated by
> > >> intel_dp->lane_count is not set. However these values cached in intel_dp
> > >> structure can be stale if link training has failed for these values
> > >> during previous modeset. Or these values can get stale since we have
> > >> now re read the DPCD registers or it can be 0 in case of connected boot
> > >> case.
> > >>
> > >> This patch validates these values against the common_rates and max lane
> > >> count values.
> > >>
> > >> This is absolutely required incase the common_rates or max lane count
> > >> are now different due to link fallback.
> > >>
> > >> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> > >> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> > >> Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> > >> ---
> > >> drivers/gpu/drm/i915/intel_dp.c | 24 +++++++++++++++++++++---
> > >> 1 file changed, 21 insertions(+), 3 deletions(-)
> > >>
> > >> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > >> index fd96a6c..51fa6b5 100644
> > >> --- a/drivers/gpu/drm/i915/intel_dp.c
> > >> +++ b/drivers/gpu/drm/i915/intel_dp.c
> > >> @@ -295,6 +295,23 @@ static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
> > >> return -1;
> > >> }
> > >>
> > >> +static bool intel_dp_link_params_is_valid(struct intel_dp *intel_dp)
> > >> +{
> > >> + int common_rates[DP_MAX_SUPPORTED_RATES];
> > >> + int link_rate_index;
> > >> +
> > >> + link_rate_index = intel_dp_link_rate_index(intel_dp,
> > >> + common_rates,
> > >> + intel_dp->link_rate);
> > >
> > > Hmm. I thought we started to store the common rates somewhere more
> > > permanent, or did I imagine that?
> >
> > That series got stalled waiting for Manasi's stuff to land... which
> > means it's now conflicting and pending rebase, and still waiting. :(
> >
> > J.
> >
>
> Hmm, yes but if you want I can work on rebasing it after these two patches
> land. That series is really required.
>
>
> >
> > >
> > >> + if (link_rate_index < 0)
> > >> + return false;
> > >> + if (!intel_dp->lane_count ||
> > >> + (intel_dp->lane_count > intel_dp_max_lane_count(intel_dp)))
> > >
> > > Needless parens.
> > >
>
> Ok, will remove that.
>
>
> > >> + return false;
> > >> +
> > >> + return true;
> > >> +}
> > >> +
> > >> int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > >> int link_rate, uint8_t lane_count)
> > >> {
> > >> @@ -4224,9 +4241,10 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> > >> if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> > >> return;
> > >>
> > >> - /* FIXME: we need to synchronize this sort of stuff with hardware
> > >> - * readout. Currently fast link training doesn't work on boot-up. */
> > >
> > > You shouldn't remove the FIXME. It's still totally valid.
> > >
>
> But that check is now incorporated in validating the params.
> So why is separate check required?
> Or are you just saying leave the FIXME comment?
Yes, leave the comment. Or better yet, move into
intel_dp_link_params_is_valid() and maybe reword a bit to something
like:
"FIXME: we need to synchronize the current link parameters with hardware
readout ..."
to make it it clear that it's actually referring to the current link
params and not something else.
>
> Manasi
>
>
> > >> - if (!intel_dp->lane_count)
> > >> + /* Validate the cached values of intel_dp->link_rate and
> > >> + * intel_dp->lane_count before attempting to retrain.
> > >> + */
> > >> + if (!intel_dp_link_params_is_valid(intel_dp))
> > >> return;
> > >>
> > >> /* Retrain if Channel EQ or CR not ok */
> > >> --
> > >> 2.1.4
> >
> > --
> > Jani Nikula, Intel Open Source Technology Center
--
Ville Syrjälä
Intel OTC
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