From 59b4d2aec473c17b5c7ab96429e352d552f45f65 Mon Sep 17 00:00:00 2001
From: Josh Pieper <jjp@pobox.com>
Date: Thu, 8 Dec 2022 10:35:34 -0500
Subject: [PATCH] Enable CAN loop delay compensation

This is necessary to support r4.5 and newer boards which use a CAN
transceiver with higher delay.
---
 fw/fdcan.cc | 14 ++++++++++++++
 fw/fdcan.h  |  9 +++++++++
 2 files changed, 23 insertions(+)

diff --git a/fw/fdcan.cc b/fw/fdcan.cc
index 1517021..a8f9e13 100644
--- a/fw/fdcan.cc
+++ b/fw/fdcan.cc
@@ -273,6 +273,20 @@ void FDCan::Reset(const Options& options) {
     mbed_die();
   }
 
+  if (options.delay_compensation) {
+    if (HAL_FDCAN_ConfigTxDelayCompensation(
+            &can, options.tdc_offset, options.tdc_filter) != HAL_OK) {
+      mbed_die();
+    }
+    if (HAL_FDCAN_EnableTxDelayCompensation(&can) != HAL_OK) {
+      mbed_die();
+    }
+  } else {
+    if (HAL_FDCAN_DisableTxDelayCompensation(&can) != HAL_OK) {
+      mbed_die();
+    }
+  }
+
   if (HAL_FDCAN_Start(&can) != HAL_OK) {
     mbed_die();
   }
diff --git a/fw/fdcan.h b/fw/fdcan.h
index 5afa3f4..4c16c38 100644
--- a/fw/fdcan.h
+++ b/fw/fdcan.h
@@ -70,6 +70,15 @@ class FDCan {
     bool restricted_mode = false;
     bool bus_monitor = false;
 
+    // We for now default to use compensation that is appropriate for
+    // the TCAN1057 with its longer delay:
+    //
+    //  start - 13 / 85Mhz ~= 152ns
+    //  min   - 1 / 85Mhz ~= 12ns
+    bool delay_compensation = true;
+    uint32_t tdc_offset = 13;
+    uint32_t tdc_filter = 1;
+
     FilterAction global_std_action = FilterAction::kAccept;
     FilterAction global_ext_action = FilterAction::kAccept;
     FilterAction global_remote_std_action = FilterAction::kAccept;