From 646a48d17f086c1c2b5adde75112bdcfaaa2827d Mon Sep 17 00:00:00 2001
From: Danny Baumann <dannybaumann@web.de>
Date: Sun, 8 Jul 2018 14:57:35 +0200
Subject: [PATCH] sdm845-common: Improve LED ramp generation algorithm.

Distribute ramp duration equally to both on and off time, use more
ramp steps (16 instead of 8) and lower green brightness to better match
brightness of red and blue (green LED is much brighter than the other
two).

Change-Id: I48d94b4020515a5cbb15486f8d44dd151b475ab0
---
 lights/Light.cpp                              | 37 ++++++++++---------
 ...rdware.light@2.0-service.oneplus_sdm845.rc |  3 ++
 2 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/lights/Light.cpp b/lights/Light.cpp
index f9bc48b..2d5b475 100644
--- a/lights/Light.cpp
+++ b/lights/Light.cpp
@@ -24,8 +24,6 @@
 #include <android-base/stringprintf.h>
 #include <fstream>
 
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
-
 namespace android {
 namespace hardware {
 namespace light {
@@ -89,26 +87,29 @@ void Light::handleRgb(const LightState& state, size_t index) {
 
     std::map<std::string, int> colorValues;
     colorValues["red"] = (stateToUse.color >> 16) & 0xff;
-    colorValues["green"] = (stateToUse.color >> 8) & 0xff;
+    // lower green brightness to adjust for the (lower) brightness of red and blue
+    colorValues["green"] = ((stateToUse.color >> 8) & 0xff) / 2;
     colorValues["blue"] = stateToUse.color & 0xff;
 
     int onMs = stateToUse.flashMode == Flash::TIMED ? stateToUse.flashOnMs : 0;
     int offMs = stateToUse.flashMode == Flash::TIMED ? stateToUse.flashOffMs : 0;
 
-    static constexpr int kRampSize = 8;
-    static constexpr int kBrightnessRamp[] = { 0, 12, 25, 37, 50, 72, 85, 100 };
-    static constexpr int kRampStepDuration = 50;
+    // LUT has 63 entries, we could theoretically use them as 3 (colors) * 21 (steps).
+    // However, the last LUT entries don't seem to behave correctly for unknown
+    // reasons, so we use 17 steps for a total of 51 LUT entries only.
+    static constexpr int kRampSteps = 16;
+    static constexpr int kRampMaxStepDurationMs = 15;
 
     auto makeLedPath = [](const std::string& led, const std::string& op) -> std::string {
         return "/sys/class/leds/" + led + "/" + op;
     };
     auto getScaledDutyPercent = [](int brightness) -> std::string {
         std::string output;
-        for (size_t i = 0; i < ARRAY_SIZE(kBrightnessRamp); i++) {
+        for (int i = 0; i <= kRampSteps; i++) {
             if (i != 0) {
                 output += ",";
             }
-            output += std::to_string(kBrightnessRamp[i] * brightness / 255);
+            output += std::to_string(i * 512 * brightness / (255 * kRampSteps));
         }
         return output;
     };
@@ -119,23 +120,25 @@ void Light::handleRgb(const LightState& state, size_t index) {
     }
 
     if (onMs > 0 && offMs > 0) {
-        int pauseHi, stepDuration;
-        if (kRampStepDuration * kRampSize * 2 > onMs) {
-            stepDuration = onMs / 2 * kRampSize;
+        int pauseLo, pauseHi, stepDuration, index = 0;
+        if (kRampMaxStepDurationMs * kRampSteps > onMs) {
+            stepDuration = onMs / kRampSteps;
             pauseHi = 0;
+            pauseLo = offMs;
         } else {
-            stepDuration = kRampStepDuration;
-            pauseHi = onMs - 2 * kRampSize * stepDuration;
+            stepDuration = kRampMaxStepDurationMs;
+            pauseHi = onMs - kRampSteps * stepDuration;
+            pauseLo = offMs - kRampSteps * stepDuration;
         }
 
         for (const auto& entry : colorValues) {
-            set(makeLedPath(entry.first, "start_idx"), 0);
+            set(makeLedPath(entry.first, "lut_flags"), 95);
+            set(makeLedPath(entry.first, "start_idx"), index);
             set(makeLedPath(entry.first, "duty_pcts"), getScaledDutyPercent(entry.second));
-            set(makeLedPath(entry.first, "pause_lo"), offMs);
-            // The led driver is configured to ramp up then ramp
-            // down the lut. This effectively doubles the ramp duration.
+            set(makeLedPath(entry.first, "pause_lo"), pauseLo);
             set(makeLedPath(entry.first, "pause_hi"), pauseHi);
             set(makeLedPath(entry.first, "ramp_step_ms"), stepDuration);
+            index += kRampSteps + 1;
         }
 
         // Start blinking
diff --git a/lights/android.hardware.light@2.0-service.oneplus_sdm845.rc b/lights/android.hardware.light@2.0-service.oneplus_sdm845.rc
index f2727d6..d7ba29d 100644
--- a/lights/android.hardware.light@2.0-service.oneplus_sdm845.rc
+++ b/lights/android.hardware.light@2.0-service.oneplus_sdm845.rc
@@ -2,6 +2,9 @@ on boot
     chown system system /sys/class/leds/red/start_idx
     chown system system /sys/class/leds/green/start_idx
     chown system system /sys/class/leds/blue/start_idx
+    chown system system /sys/class/leds/red/lut_flags
+    chown system system /sys/class/leds/green/lut_flags
+    chown system system /sys/class/leds/blue/lut_flags
 
 service light-hal-2-0 /system/bin/hw/android.hardware.light@2.0-service.oneplus_sdm845
     class hal