[Intel-gfx] [PATCH 07/11] drm/i915: Update intel_dp_hpd_pulse() for non-MST operation

[Paulo Zanoni]

2015-04-10 13:12 GMT-03:00 Todd Previte <tprevite at gmail.com>:
> Update the hot plug function to handle the SST case. Instead of placing
> the SST case within the long/short pulse block, it is now handled after
> determining that MST mode is not in use. This way, the topology management
> layer can handle any MST-related operations while SST operations are still
> correctly handled afterwards.
>
> This patch also corrects the problem of SST mode only being handled in the
> case of a short (0.5ms - 1.0ms) HPD pulse. For compliance testing purposes
> both short and long pulses are used by the different tests, thus both cases
> need to be addressed for SST.
>
> This patch replaces [PATCH 10/10] drm/i915: Fix intel_dp_hot_plug() in the
> previous compliance testing patch sequence. Review feedback on that patch
> indicated that updating intel_dp_hot_plug() was not the correct place for
> the test handler.
>
> For the SST case, the main stream is disabled for long HPD pulses as this
> generally indicates either a connect/disconnect event or link failure. For
> a number of case in compliance testing, the source is required to disable
> the main link upon detection of a long HPD.
>
> V2:
> - N/A
> V3:
> - Place the SST mode link status check into the mst_fail case
> - Remove obsolete comment regarding SST mode operation
> - Removed an erroneous line of code that snuck in during rebasing
> V4:
> - Added a disable of the main stream (DP transport) for the long pulse case
>   for SST to support compliance testing
> V5:
> - Reworked SST handling to support tests 4.2.2.7 and 4.2.2.8
> V6:
> - Reformatted a comment
>
> Signed-off-by: Todd Previte <tprevite at gmail.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 77b6b15..ba2da44 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4572,29 +4572,26 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>                         if (intel_dp_check_mst_status(intel_dp) == -EINVAL)
>                                 goto mst_fail;
>                 }
> -
> -               if (!intel_dp->is_mst) {
> -                       /*
> -                        * we'll check the link status via the normal hot plug path later -
> -                        * but for short hpds we should check it now
> -                        */
> -                       drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> -                       intel_dp_check_link_status(intel_dp);
> -                       drm_modeset_unlock(&dev->mode_config.connection_mutex);
> -               }
>         }

Shouldn't the code be moved to exactly this spot instead of after the
put_power label? Why would we want to call check_link_status in case
we goto mst_fail? In case there is a valid reason, maybe it would be
better to do a big reorganization of this function because it's going
to start looking very weird - or at least rename the labels.

Also, for the long_hpd case, I see that check_link_status() will redo
some of the stuff we already did on this function, such as get_dpcd().
And if you follow my advice on patch 2, you will end up having even
more repeated code. I think you could try to do a careful analysis
here to make sure we're not calling stuff twice here, especially since
some of those operations are potentially slow.

>
>         ret = IRQ_HANDLED;
>
>         goto put_power;
>  mst_fail:
> -       /* if we were in MST mode, and device is not there get out of MST mode */
>         if (intel_dp->is_mst) {
> +               /* if we were in MST mode, and device is not there get out of MST mode */

I don't see the need for changes such as the one above - I saw similar
cases in other patches you submitted. I often use git blame on
comments in order to be able to see the whole context of the change,
and a simple change like this makes it harder to blame. Also, you're
not even fixing the 80 column problem here. And I do prefer the
comment on top of the if statement.


>                 DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n", intel_dp->is_mst, intel_dp->mst_mgr.mst_state);
>                 intel_dp->is_mst = false;
>                 drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
>         }
>  put_power:
> +       /* SST mode - handle short/long pulses here */
> +       if (!intel_dp->is_mst) {
> +               drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +               intel_dp_check_link_status(intel_dp);
> +               drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +               ret = IRQ_HANDLED;
> +       }
>         intel_display_power_put(dev_priv, power_domain);
>
>         return ret;
> --
> 1.9.1
>
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-- 
Paulo Zanoni