TCAN4550 Bus Off Recovery (#628)

* Fix debug build. * Move TX FIFO flush to the bus-off state. * Handle bus-off recovery. * Add commentary about the memory write contract.
bakerstu · Jun 9, 2022 · b496173 · b496173
1 parent 327f370
commit b496173
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Showing 2 changed files with 23 additions and 7 deletions.
diff --git a/src/freertos_drivers/common/TCAN4550Can.cxx b/src/freertos_drivers/common/TCAN4550Can.cxx
@@ -650,7 +650,7 @@ void *TCAN4550Can::entry()
             spiStatus_ = register_read(STATUS);
             status_ = register_read(INTERRUPT_STATUS);
 
-            MRAMMessage msg;
+            MRAMSPIMessage msg;
             msg.cmd = READ;
             msg.addrH = 0x10;
             msg.addrL = 0x00;
@@ -659,7 +659,7 @@ void *TCAN4550Can::entry()
             spi_ioc_transfer xfer[2];
             xfer[0].tx_buf = (unsigned long)&msg;
             xfer[0].rx_buf = 0;
-            xfer[0].len = sizeof(MRAMMessage);
+            xfer[0].len = sizeof(MRAMSPIMessage);
             xfer[1].tx_buf = 0;
             xfer[1].rx_buf = (unsigned long)regs_;
             xfer[1].len = sizeof(regs_);
@@ -712,11 +712,6 @@ void *TCAN4550Can::entry()
                     // error passive state
                     ++softErrorCount;
                     state_ = CAN_STATE_BUS_PASSIVE;
-
-                    // cancel TX FIFO buffers
-                    register_write(TXBCR, TX_FIFO_BUFFERS_MASK);
-
-                    txBuf->signal_condition();
                 }
                 else
                 {
@@ -730,6 +725,23 @@ void *TCAN4550Can::entry()
                     // bus off
                     ++busOffCount;
                     state_ = CAN_STATE_BUS_OFF;
+                    // attempt recovery
+                    Cccr cccr;
+                    do
+                    {
+                        cccr.data = 0;
+                        register_write(CCCR, cccr.data);
+                        cccr.data = register_read(CCCR);
+                    } while (cccr.init == 1);
+
+                    // cancel TX FIFO buffers
+                    register_write(TXBCR, TX_FIFO_BUFFERS_MASK);
+
+                    txBuf->signal_condition();
+                }
+                else
+                {
+                    state_ = CAN_STATE_ACTIVE;
                 }
             }
         }

diff --git a/src/freertos_drivers/common/TCAN4550Can.hxx b/src/freertos_drivers/common/TCAN4550Can.hxx
@@ -1124,6 +1124,10 @@ private:
     MCANInterrupt mcanInterruptEnable_; ///< shadow for the interrupt enable
     uint32_t txCompleteMask_; ///< shadow for the transmit complete buffer mask
     uint8_t state_; ///< present bus state
+
+    // These bitmasks are protected from a read-modify-write race condition
+    // because they are only set from a thread context that holds the SPI bus
+    // mutex.
     uint8_t txPending_ : 1; ///< waiting on a TX active event
     uint8_t rxPending_ : 1; ///< waiting on a RX active event