On Thu, 27 Aug 2015, Sivakumar Thulasimani <sivakumar.thulasimani@xxxxxxxxx> wrote:
> From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@xxxxxxxxx>
>
> This patch checks for changes in sink count between short pulse
> hpds and forces full detect when there is a change.
>
> This will allow both detection of hotplug and unplug of panels
> through dongles that give only short pulse for such events.
>
> v2: changed variable type from u8 to bool (Jani)
> return immediately if perform_full_detect is set(Siva)
The general idea LGTM, however see below.
>
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 27 ++++++++++++++++++++++-----
> 1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 834f513..279e52c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4370,26 +4370,39 @@ go_again:
> * 4. Check link status on receipt of hot-plug interrupt
> */
> static void
> -intel_dp_check_link_status(struct intel_dp *intel_dp)
> +intel_dp_check_link_status(struct intel_dp *intel_dp, bool *perform_full_detect)
> {
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> struct intel_crtc *crtc =
> to_intel_crtc(dp_to_dig_port(intel_dp)->base.base.crtc);
> u8 sink_irq_vector;
> + u8 old_sink_count = intel_dp->sink_count;
> + bool ret;
> u8 link_status[DP_LINK_STATUS_SIZE];
>
> WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>
> + *perform_full_detect = false;
> +
> /* Try to read receiver status if the link appears to be up */
> if (!intel_dp_get_link_status(intel_dp, link_status)) {
> return;
> }
>
> - /* Now read the DPCD to see if it's actually running */
> - if (!intel_dp_get_dpcd(intel_dp)) {
> + /* Now read the DPCD to see if it's actually running
> + * Don't return immediately if dpcd read failed,
> + * if sink count was 1 and dpcd read failed we need
> + * to do full detection
> + */
> + ret = intel_dp_get_dpcd(intel_dp);
> +
> + if (old_sink_count != intel_dp->sink_count)
> + *perform_full_detect = true;
The point I was trying to make earlier is that how can you trust
intel_dp->sink_count if intel_dp_get_dpcd failed? You don't know where
it failed, and ->sink_count may or may not have changed. Maybe it has
changed for real but you didn't have a chance to read it just yet.
> +
> + /* No need to proceed if we are going to do full detect */
> + if (!ret || *perform_full_detect)
> return;
> - }
So if you're returning because of !ret, *perform_full_detect may be true
or false, you don't know. I'd like the code to be explicit about what
you want the caller to do when intel_dp_get_dpcd returns false, full
detect or not.
BR,
Jani.
>
> if (!intel_encoder->base.crtc)
> return;
> @@ -5031,13 +5044,17 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
> }
>
> if (!intel_dp->is_mst) {
> + bool full_detect;
> /*
> * 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);
> + intel_dp_check_link_status(intel_dp, &full_detect);
> drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> + if (full_detect)
> + goto put_power;
> }
> }
>
> --
> 1.7.9.5
>
--
Jani Nikula, Intel Open Source Technology Center
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