iwlwifi: mvm: rs: fix and cleanup rs_get_rate_action

Change the down/upscale decision logic a bit to be based
on different success ratio thresholds. This fixes the implementation
compared to the rate scale algorithm which was planned to yield
optimal results. Also fix a case where a lower rate wasn't explored
despite being a potential for better throughput.
While at it rewrite rs_get_rate_action to be more clear and clean.

Cc: <stable@vger.kernel.org> [3.14]
Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

2 files changed, 60 insertions, 68 deletions

diff --git a/drivers/net/wireless/iwlwifi/mvm/rs.c b/drivers/net/wireless/iwlwifi/mvm/rs.c
index cd32ad54384e..97b8fac214a1 100644
--- a/drivers/net/wireless/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.c
@@ -1658,85 +1658,76 @@ static enum rs_action rs_get_rate_action(struct iwl_mvm *mvm,
 {
         enum rs_action action = RS_ACTION_STAY;
 
-        /* Too many failures, decrease rate */
         if ((sr <= RS_SR_FORCE_DECREASE) || (current_tpt == 0)) {
                 IWL_DEBUG_RATE(mvm,
-                               "decrease rate because of low SR\n");
-                action = RS_ACTION_DOWNSCALE;
-        /* No throughput measured yet for adjacent rates; try increase. */
-        } else if ((low_tpt == IWL_INVALID_VALUE) &&
-                   (high_tpt == IWL_INVALID_VALUE)) {
-                if (high != IWL_RATE_INVALID && sr >= IWL_RATE_INCREASE_TH) {
-                        IWL_DEBUG_RATE(mvm,
-                                       "Good SR and no high rate measurement. "
-                                       "Increase rate\n");
-                        action = RS_ACTION_UPSCALE;
-                } else if (low != IWL_RATE_INVALID) {
-                        IWL_DEBUG_RATE(mvm,
-                                       "Remain in current rate\n");
-                        action = RS_ACTION_STAY;
-                }
+                               "Decrease rate because of low SR\n");
+                return RS_ACTION_DOWNSCALE;
         }
 
-        /* Both adjacent throughputs are measured, but neither one has better
-         * throughput; we're using the best rate, don't change it!
-         */
-        else if ((low_tpt != IWL_INVALID_VALUE) &&
-                 (high_tpt != IWL_INVALID_VALUE) &&
-                 (low_tpt < current_tpt) &&
-                 (high_tpt < current_tpt)) {
+        if ((low_tpt == IWL_INVALID_VALUE) &&
+            (high_tpt == IWL_INVALID_VALUE) &&
+            (high != IWL_RATE_INVALID)) {
                 IWL_DEBUG_RATE(mvm,
-                               "Both high and low are worse. "
-                               "Maintain rate\n");
-                action = RS_ACTION_STAY;
+                               "No data about high/low rates. Increase rate\n");
+                return RS_ACTION_UPSCALE;
         }
 
-        /* At least one adjacent rate's throughput is measured,
-         * and may have better performance.
-         */
-        else {
-                /* Higher adjacent rate's throughput is measured */
-                if (high_tpt != IWL_INVALID_VALUE) {
-                        /* Higher rate has better throughput */
-                        if (high_tpt > current_tpt &&
-                            sr >= IWL_RATE_INCREASE_TH) {
-                                IWL_DEBUG_RATE(mvm,
-                                               "Higher rate is better and good "
-                                               "SR. Increate rate\n");
-                                action = RS_ACTION_UPSCALE;
-                        } else {
-                                IWL_DEBUG_RATE(mvm,
-                                               "Higher rate isn't better OR "
-                                               "no good SR. Maintain rate\n");
-                                action = RS_ACTION_STAY;
-                        }
+        if ((high_tpt == IWL_INVALID_VALUE) &&
+            (high != IWL_RATE_INVALID) &&
+            (low_tpt != IWL_INVALID_VALUE) &&
+            (low_tpt < current_tpt)) {
+                IWL_DEBUG_RATE(mvm,
+                               "No data about high rate and low rate is worse. Increase rate\n");
+                return RS_ACTION_UPSCALE;
+        }
 
-                /* Lower adjacent rate's throughput is measured */
-                } else if (low_tpt != IWL_INVALID_VALUE) {
-                        /* Lower rate has better throughput */
-                        if (low_tpt > current_tpt) {
-                                IWL_DEBUG_RATE(mvm,
-                                               "Lower rate is better. "
-                                               "Decrease rate\n");
-                                action = RS_ACTION_DOWNSCALE;
-                        } else if (sr >= IWL_RATE_INCREASE_TH) {
-                                IWL_DEBUG_RATE(mvm,
-                                               "Lower rate isn't better and "
-                                               "good SR. Increase rate\n");
-                                action = RS_ACTION_UPSCALE;
-                        }
-                }
+        if ((high_tpt != IWL_INVALID_VALUE) &&
+            (high_tpt > current_tpt)) {
+                IWL_DEBUG_RATE(mvm,
+                               "Higher rate is better. Increate rate\n");
+                return RS_ACTION_UPSCALE;
         }
 
-        /* Sanity check; asked for decrease, but success rate or throughput
-         * has been good at old rate.  Don't change it.
-         */
-        if ((action == RS_ACTION_DOWNSCALE) && (low != IWL_RATE_INVALID) &&
-            ((sr > IWL_RATE_HIGH_TH) ||
-             (current_tpt > (100 * tbl->expected_tpt[low])))) {
+        if ((low_tpt != IWL_INVALID_VALUE) &&
+            (high_tpt != IWL_INVALID_VALUE) &&
+            (low_tpt < current_tpt) &&
+            (high_tpt < current_tpt)) {
                 IWL_DEBUG_RATE(mvm,
-                               "Sanity check failed. Maintain rate\n");
-                action = RS_ACTION_STAY;
+                               "Both high and low are worse. Maintain rate\n");
+                return RS_ACTION_STAY;
+        }
+
+        if ((low_tpt != IWL_INVALID_VALUE) &&
+            (low_tpt > current_tpt)) {
+                IWL_DEBUG_RATE(mvm,
+                               "Lower rate is better\n");
+                action = RS_ACTION_DOWNSCALE;
+                goto out;
+        }
+
+        if ((low_tpt == IWL_INVALID_VALUE) &&
+            (low != IWL_RATE_INVALID)) {
+                IWL_DEBUG_RATE(mvm,
+                               "No data about lower rate\n");
+                action = RS_ACTION_DOWNSCALE;
+                goto out;
+        }
+
+        IWL_DEBUG_RATE(mvm, "Maintain rate\n");
+
+out:
+        if ((action == RS_ACTION_DOWNSCALE) && (low != IWL_RATE_INVALID)) {
+                if (sr >= RS_SR_NO_DECREASE) {
+                        IWL_DEBUG_RATE(mvm,
+                                       "SR is above NO DECREASE. Avoid downscale\n");
+                        action = RS_ACTION_STAY;
+                } else if (current_tpt > (100 * tbl->expected_tpt[low])) {
+                        IWL_DEBUG_RATE(mvm,
+                                       "Current TPT is higher than max expected in low rate. Avoid downscale\n");
+                        action = RS_ACTION_STAY;
+                } else {
+                        IWL_DEBUG_RATE(mvm, "Decrease rate\n");
+                }
         }
 
         return action;
diff --git a/drivers/net/wireless/iwlwifi/mvm/rs.h b/drivers/net/wireless/iwlwifi/mvm/rs.h
index 9892d92d5901..fbb476aadb22 100644
--- a/drivers/net/wireless/iwlwifi/mvm/rs.h
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.h
@@ -156,6 +156,7 @@ enum {
 #define IWL_RATE_HIGH_TH                10880   /*  85% */
 #define IWL_RATE_INCREASE_TH            6400    /*  50% */
 #define RS_SR_FORCE_DECREASE            1920    /*  15% */
+#define RS_SR_NO_DECREASE               10880   /*  85% */
 
 #define LINK_QUAL_AGG_TIME_LIMIT_DEF    (4000) /* 4 milliseconds */
 #define LINK_QUAL_AGG_TIME_LIMIT_MAX    (8000)