rp2040: Initial support for CANbus

Add support for CANbus on the rp2040 using the can2040 "software
canbus" implementation.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/rp2040/Kconfig

@@ -83,6 +83,19 @@ choice
     config RP2040_SERIAL_UART0
         bool "Serial (on UART0 GPIO1/GPIO0)"
         select SERIAL
+    config RP2040_CANBUS
+        bool "CAN bus"
+        select CANSERIAL
 endchoice
 
+config RP2040_CANBUS_GPIO_RX
+    int "CAN RX gpio number" if CANBUS
+    default 4
+    range 0 29
+
+config RP2040_CANBUS_GPIO_TX
+    int "CAN TX gpio number" if CANBUS
+    default 5
+    range 0 29
+
 endif

src/rp2040/Makefile

@@ -3,10 +3,10 @@
 # Setup the toolchain
 CROSS_PREFIX=arm-none-eabi-
 
-dirs-y += src/rp2040 src/generic lib/rp2040/elf2uf2
+dirs-y += src/rp2040 src/generic lib/rp2040/elf2uf2 lib/fast-hash lib/can2040
 
 CFLAGS += -mcpu=cortex-m0plus -mthumb -Ilib/cmsis-core
-CFLAGS += -Ilib/rp2040 -Ilib/rp2040/cmsis_include
+CFLAGS += -Ilib/rp2040 -Ilib/rp2040/cmsis_include -Ilib/fast-hash -Ilib/can2040
 
 CFLAGS_klipper.elf += --specs=nano.specs --specs=nosys.specs
 CFLAGS_klipper.elf += -T $(OUT)src/rp2040/rp2040_link.ld
@@ -19,6 +19,9 @@ src-y += generic/timer_irq.c rp2040/timer.c rp2040/bootrom.c
 src-$(CONFIG_USBSERIAL) += rp2040/usbserial.c generic/usb_cdc.c
 src-$(CONFIG_USBSERIAL) += rp2040/chipid.c
 src-$(CONFIG_SERIAL) += rp2040/serial.c generic/serial_irq.c
+src-$(CONFIG_CANSERIAL) += rp2040/can.c rp2040/chipid.c ../lib/can2040/can2040.c
+src-$(CONFIG_CANSERIAL) += generic/canserial.c generic/canbus.c
+src-$(CONFIG_CANSERIAL) += ../lib/fast-hash/fasthash.c
 src-$(CONFIG_HAVE_GPIO_HARD_PWM) += rp2040/hard_pwm.c
 src-$(CONFIG_HAVE_GPIO_SPI) += rp2040/spi.c
 src-$(CONFIG_HAVE_GPIO_I2C) += rp2040/i2c.c

src/rp2040/can.c

@@ -0,0 +1,78 @@
+// Serial over CAN emulation for rp2040 using can2040 software canbus
+//
+// Copyright (C) 2022  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdint.h> // uint32_t
+#include <string.h> // memcpy
+#include "autoconf.h" // CONFIG_CANBUS_FREQUENCY
+#include "board/armcm_boot.h" // armcm_enable_irq
+#include "board/io.h" // readl
+#include "can2040.h" // can2040_setup
+#include "command.h" // DECL_CONSTANT_STR
+#include "fasthash.h" // fasthash64
+#include "generic/canbus.h" // canbus_notify_tx
+#include "generic/canserial.h" // CANBUS_ID_ADMIN
+#include "hardware/structs/resets.h" // RESETS_RESET_PIO0_BITS
+#include "internal.h" // DMA_IRQ_0_IRQn
+#include "sched.h" // DECL_INIT
+
+#define GPIO_STR_CAN_RX "gpio" __stringify(CONFIG_RP2040_CANBUS_GPIO_RX)
+#define GPIO_STR_CAN_TX "gpio" __stringify(CONFIG_RP2040_CANBUS_GPIO_TX)
+DECL_CONSTANT_STR("RESERVE_PINS_CAN", GPIO_STR_CAN_RX "," GPIO_STR_CAN_TX);
+
+static struct can2040 cbus;
+
+// Transmit a packet
+int
+canbus_send(struct canbus_msg *msg)
+{
+    int ret = can2040_transmit(&cbus, (void*)msg);
+    if (ret < 0)
+        return -1;
+    return CANMSG_DATA_LEN(msg);
+}
+
+// Setup the receive packet filter
+void
+canbus_set_filter(uint32_t id)
+{
+    // Filter not implemented (and not necessary)
+}
+
+// can2040 callback function - handle rx and tx notifications
+static void
+can2040_cb(struct can2040 *cd, uint32_t notify, struct can2040_msg *msg)
+{
+    if (notify & CAN2040_NOTIFY_TX) {
+        canbus_notify_tx();
+        return;
+    }
+    if (notify & CAN2040_NOTIFY_RX)
+        canbus_process_data((void*)msg);
+}
+
+// Main PIO irq handler
+void
+PIOx_IRQHandler(void)
+{
+    can2040_pio_irq_handler(&cbus);
+}
+
+void
+can_init(void)
+{
+    // Setup canbus
+    can2040_setup(&cbus, 0);
+    can2040_callback_config(&cbus, can2040_cb);
+
+    // Enable irqs
+    armcm_enable_irq(PIOx_IRQHandler, PIO0_IRQ_0_IRQn, 1);
+
+    // Start canbus
+    uint32_t pclk = get_pclock_frequency(RESETS_RESET_PIO0_RESET);
+    can2040_start(&cbus, pclk, CONFIG_CANBUS_FREQUENCY
+                  , CONFIG_RP2040_CANBUS_GPIO_RX, CONFIG_RP2040_CANBUS_GPIO_TX);
+}
+DECL_INIT(can_init);

src/rp2040/chipid.c

@@ -4,11 +4,10 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#define CHIP_UID_LEN 8
-
 #include <string.h> // memcpy
 #include "autoconf.h" // CONFIG_USB_SERIAL_NUMBER_CHIPID
 #include "board/irq.h" // irq_disable, irq_enable
+#include "board/canserial.h" // canserial_set_uuid
 #include "generic/usb_cdc.h" // usb_fill_serial
 #include "generic/usbstd.h" // usb_string_descriptor
 #include "sched.h" // DECL_INIT
@@ -16,6 +15,8 @@
 #include "hardware/structs/ssi.h" // ssi_hw
 #include "internal.h"
 
+#define CHIP_UID_LEN 8
+
 static struct {
     struct usb_string_descriptor desc;
     uint16_t data[CHIP_UID_LEN * 2];
@@ -120,13 +121,15 @@ read_unique_id(uint8_t *out)
 void
 chipid_init(void)
 {
-    if (!CONFIG_USB_SERIAL_NUMBER_CHIPID)
+    if (!(CONFIG_USB_SERIAL_NUMBER_CHIPID || CONFIG_CANBUS))
         return;
 
     uint8_t data[8] = {0};
     read_unique_id(data);
 
-    usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data)
-                    , data);
+    if (CONFIG_USB_SERIAL_NUMBER_CHIPID)
+        usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data), data);
+    if (CONFIG_CANBUS)
+        canserial_set_uuid(data, CHIP_UID_LEN);
 }
 DECL_INIT(chipid_init);