From 2cc6514583be7137a58005418740eb58a30a0389 Mon Sep 17 00:00:00 2001
From: Phil Howard <phil@gadgetoid.com>
Date: Thu, 26 Aug 2021 16:35:05 +0100
Subject: [PATCH] Slow set/clr_bit writes a little

We chased a bug with handling/clearing interrupts on Encoder into the depths of madness, finding that a Debug build would magically fix the bug.

Turns out it was probably just us being a little aggressive with the poor little MS51-based Encoder driver.

* Fix delays to be more delayey.
* Replace big 'ol loop and boolean with straight up checks and an early exit- the bit-addressed regs are never going to change
---
 drivers/ioexpander/ioexpander.cpp | 46 ++++++++++++-------------------
 1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/drivers/ioexpander/ioexpander.cpp b/drivers/ioexpander/ioexpander.cpp
index dec135a5..7a7450c3 100644
--- a/drivers/ioexpander/ioexpander.cpp
+++ b/drivers/ioexpander/ioexpander.cpp
@@ -756,27 +756,19 @@ namespace pimoroni {
   }
 
   void IOExpander::set_bits(uint8_t reg, uint8_t bits) {
-    // Set the specified bits (using a mask) in a register.
-
-    // Deal with special case registers first
-    bool reg_in_bit_addressed_regs = false;
-    for(uint8_t i = 0; i < NUM_BIT_ADDRESSED_REGISTERS; i++) {
-      if(BIT_ADDRESSED_REGS[i] == reg) {
+    if(reg == reg::P0 || reg == reg::P1 || reg == reg::P2 || reg == reg::P3) {
         for(uint8_t bit = 0; bit < 8; bit++) {
-          if(bits & (1 << bit))
+          if(bits & (1 << bit)) {
             i2c->reg_write_uint8(address, reg, 0b1000 | (bit & 0b111));
+            sleep_us(50);
+          }
         }
-        reg_in_bit_addressed_regs = true;
-        break;
-      }
+        return;
     }
 
-    // Now deal with any other registers
-    if(!reg_in_bit_addressed_regs) {
-      uint8_t value = i2c->reg_read_uint8(address, reg);
-      sleep_us(10);
-      i2c->reg_write_uint8(address, reg, value | bits);
-    }
+    uint8_t value = i2c->reg_read_uint8(address, reg);
+    sleep_us(50);
+    i2c->reg_write_uint8(address, reg, value | bits);
   }
 
   void IOExpander::set_bit(uint8_t reg, uint8_t bit) {
@@ -785,24 +777,20 @@ namespace pimoroni {
   }
 
   void IOExpander::clr_bits(uint8_t reg, uint8_t bits) {
-    bool reg_in_bit_addressed_regs = false;
-    for(uint8_t i = 0; i < NUM_BIT_ADDRESSED_REGISTERS; i++) {
-      if(BIT_ADDRESSED_REGS[i] == reg) {
-        for(uint8_t bit = 0; bit < 8; bit++) {
-          if(bits & (1 << bit))
-            i2c->reg_write_uint8(address, reg, 0b0000 | (bit & 0b111));
+    if(reg == reg::P0 || reg == reg::P1 || reg == reg::P2 || reg == reg::P3) {
+      for(uint8_t bit = 0; bit < 8; bit++) {
+        if(bits & (1 << bit)) {
+          i2c->reg_write_uint8(address, reg, 0b0000 | (bit & 0b111));
+          sleep_us(50);
         }
-        reg_in_bit_addressed_regs = true;
-        break;
       }
+      return;
     }
 
     // Now deal with any other registers
-    if(!reg_in_bit_addressed_regs) {
-      uint8_t value = i2c->reg_read_uint8(address, reg);
-      sleep_us(10);
-      i2c->reg_write_uint8(address, reg, value & ~bits);
-    }
+    uint8_t value = i2c->reg_read_uint8(address, reg);
+    sleep_us(50);
+    i2c->reg_write_uint8(address, reg, value & ~bits);
   }
 
   void IOExpander::clr_bit(uint8_t reg, uint8_t bit) {