On Tue, 06 Dec 2016, Manasi Navare manasi.d.navare@intel.com wrote:
If link training fails, then we need to fallback to lower link rate first and if link training fails at RBR, then fallback to lower lane count. This function finds the next lower link rate/lane count value after link training failure and limits the max link_rate and lane_count values to these fallback values.
v6:
- Cap the max link rate and lane count to the max
values obtained during fallback link training (Daniel Vetter) v5:
- Start the fallback at the lane count value passed not
the max lane count (Jani Nikula) v4:
- Remove the redundant variable link_train_failed
v3:
- Remove fallback_link_rate_index variable, just obtain
that using the helper intel_dp_link_rate_index (Jani Nikula) v2: Squash the patch that returns the link rate index (Jani Nikula)
Acked-by: Tony Cheng tony.cheng@amd.com Acked-by: Harry Wentland harry.wentland@amd.com Cc: Ville Syrjala ville.syrjala@linux.intel.com Cc: Jani Nikula jani.nikula@linux.intel.com Cc: Daniel Vetter daniel.vetter@intel.com Signed-off-by: Manasi Navare manasi.d.navare@intel.com
drivers/gpu/drm/i915/intel_dp.c | 40 ++++++++++++++++++++++++++++++++++++++++ drivers/gpu/drm/i915/intel_drv.h | 2 ++ 2 files changed, 42 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 434dc7d..b5c7526f 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -278,6 +278,46 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp, common_rates); }
+static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
int *common_rates, int link_rate)+{
- int common_len;
- int index;
- common_len = intel_dp_common_rates(intel_dp, common_rates);
- for (index = 0; index < common_len; index++) {
if (link_rate == common_rates[common_len - index - 1])return common_len - index - 1;
Probably somewhere in the history of the patch series there was a time when it was necessary to search for the rates in reverse order. What possible benefit could that offer at this point?
- }
- return -1;
+}
+int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
int link_rate, uint8_t lane_count)+{
- int common_rates[DP_MAX_SUPPORTED_RATES] = {};
No need to initialize because you initialize it a couple of lines later.
- int common_len;
- int link_rate_index = -1;
No need to initialize because you initialize it a couple of lines later.
- common_len = intel_dp_common_rates(intel_dp, common_rates);
- link_rate_index = intel_dp_link_rate_index(intel_dp,
common_rates,link_rate);
Please stop and think, and don't rush each new iteration of the patches.
What's wrong with the above lines? Please think about it. Answer at the end of the mail (*).
- if (link_rate_index > 0) {
intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);intel_dp->max_sink_lane_count = lane_count;- } else if (lane_count > 1) {
intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);intel_dp->max_sink_lane_count = lane_count >> 1;- } else {
DRM_ERROR("Link Training Unsuccessful\n");return -1;- }
- return 0;
+}
static enum drm_mode_status intel_dp_mode_valid(struct drm_connector *connector, struct drm_display_mode *mode) diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index b6526ad..47e3671 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port, void intel_dp_set_link_params(struct intel_dp *intel_dp, int link_rate, uint8_t lane_count, bool link_mst); +int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
int link_rate, uint8_t lane_count);void intel_dp_start_link_train(struct intel_dp *intel_dp); void intel_dp_stop_link_train(struct intel_dp *intel_dp); void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
(*) You do intel_dp_common_rates(intel_dp, common_rates) twice, for no reason at all.