On Fri, Jul 20, 2018 at 01:28:44PM -0700, Rodrigo Vivi wrote:
> On Fri, Jul 20, 2018 at 01:15:59PM -0700, Nathan Ciobanu wrote:
> > Limit the link training clock recovery loop to 10 attempts at
> > LANEx_CR_DONE per DP 1.4 spec section 3.5.1.2.2 and 80 attempts for
> > pre-DP 1.4 (4 voltage levels x 4 preemphasis levels x
> > x 5 identical voltages tries). Some faulty USB-C MST hubs can
> > cause us to get stuck in this loop indefinitely requesting something
> > like:
> >
> > voltage swing: 0, pre-emphasis level: 2
> > voltage swing: 1, pre-emphasis level: 2
> > voltage swing: 0, pre-emphasis level: 3
> >
> > over and over so max_vswing would never be reached,
> > drm_dp_clock_recovery_ok() would never return true and voltage_tries
> > would always get reset to 1. The driver sends those values to the hub
> > but the hub keeps requesting new values every time.
> >
> > Changes in v2:
> > - updated commit message (DK, Manasi)
> > - defined DP_DP14_MAX_CR_TRIES (Marc)
> > - made the loop iterate for max 10 times (Rodrigo, Marc)
> >
> > Changes in v3:
> > - changed error message to use DP_DP14_MAX_CR_TRIES
> >
> > Changes in v4:
> > - Updated the title to reflect the change
> > - Updated the commit message
> > - Added 80 attempts for pre-DP 1.4 devices
> >
> > Changes in v5:
> > - Removed DP_DP14_MAX_CR_TRIES from drm
> >
> > v6: Updated comment to match kernel style (Rodrigo)
>
> thanks... you could've added my rv-b directly as well ;)
Why should it be simple when I can make it complicated, right? :D.
Hopefully less noob mistakes next time.
>
> >
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandi...@intel.com>
> > Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
> > Cc: Marc Herbert <marc.herb...@intel.com>
> > Cc: Manasi Navare <manasi.d.nav...@intel.com>
> > Signed-off-by: Nathan Ciobanu <nathan.d.ciob...@linux.intel.com>
>
> anyway
>
> Reviewed-by: Rodrigo Vivi <rodrigo.v...@intel.com>
>
> > ---
> > drivers/gpu/drm/i915/intel_dp_link_training.c | 17 +++++++++++++++--
> > 1 file changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 4da6e33c7fa1..299cad5632ed 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -129,7 +129,7 @@ static bool intel_dp_link_max_vswing_reached(struct
> > intel_dp *intel_dp)
> > intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
> > {
> > uint8_t voltage;
> > - int voltage_tries, max_vswing_tries;
> > + int voltage_tries, max_vswing_tries, cr_tries, max_cr_tries;
> > uint8_t link_config[2];
> > uint8_t link_bw, rate_select;
> >
> > @@ -170,9 +170,20 @@ static bool intel_dp_link_max_vswing_reached(struct
> > intel_dp *intel_dp)
> > return false;
> > }
> >
> > + /*
> > + * DP 1.4 spec clock recovery retries defined but
> > + * for devices pre-DP 1.4 we set the retry limit
> > + * to 4 (voltage levels) x 4 (preemphasis levels) x
> > + * x 5 (same voltage retries) = 80 (max iterations)
> > + */
> > + if (intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
> > + max_cr_tries = 10;
> > + else
> > + max_cr_tries = 80;
> > +
> > voltage_tries = 1;
> > max_vswing_tries = 0;
> > - for (;;) {
> > + for (cr_tries = 0; cr_tries < max_cr_tries; ++cr_tries) {
> > uint8_t link_status[DP_LINK_STATUS_SIZE];
> >
> > drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
> > @@ -216,6 +227,8 @@ static bool intel_dp_link_max_vswing_reached(struct
> > intel_dp *intel_dp)
> > ++max_vswing_tries;
> >
> > }
> > + DRM_ERROR("Failed clock recovery %d times, giving up!\n", max_cr_tries);
> > + return false;
> > }
> >
> > /*
> > --
> > 1.9.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
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