### Resources
* [Photos of breadboard wiring](https://photos.app.goo.gl/1UUAHhRngzwiVWha9)
* [MCP2515 breakout board from Amazon](https://smile.amazon.com/gp/product/B01HXI5LH8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1)
* [BeagleBone Black headers](https://elinux.org/Beagleboard:Cape_Expansion_Headers)
* [Macchina M2 schematics](https://github.com/macchina/m2-hardware/tree/master/M2-B)


### /boot/uEnv.txt
```
uname_r=4.14.78-bone17

enable_uboot_overlays=1
uboot_overlay_addr0=/lib/firmware/BB-SPIDEV0-00A0.dtbo
uboot_overlay_addr1=/lib/firmware/MCP2515.dtbo
disable_uboot_overlay_emmc=1
disable_uboot_overlay_video=1
disable_uboot_overlay_audio=1
disable_uboot_overlay_wireless=1
disable_uboot_overlay_adc=1
uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-14-TI-00A0.dtbo
enable_uboot_cape_universal=1

cmdline=coherent_pool=1M net.ifnames=0 quiet
```
#### device tree overlays
* [MCP2515.dts](https://github.com/battlesnake/beaglebone-spi0-mcp2515/blob/master/MCP2515.dts)
  * [related mailing list discussion](https://groups.google.com/d/msg/beagleboard/nyyq1wQtGQc/iwGNUBM0EwAJ)
* [BB-SPIDEV0-00A0.dts](https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-SPIDEV0-00A0.dts)
#### u-boot log
```
loading /boot/vmlinuz-4.14.78-bone17 ...
7438848 bytes read in 547 ms (13 MiB/s)
uboot_overlays: [uboot_base_dtb=am335x-boneblack-uboot-univ.dtb] ...
uboot_overlays: [uboot_base_dtb=am335x-boneblack-uboot.dtb] ...
uboot_overlays: Switching too: dtb=am335x-boneblack-uboot.dtb ...
loading /boot/dtbs/4.14.78-bone17/am335x-boneblack-uboot.dtb ...
58502 bytes read in 97 ms (588.9 KiB/s)
uboot_overlays: [fdt_buffer=0x60000] ...
uboot_overlays: loading /lib/firmware/BB-SPIDEV0-00A0.dtbo ...
1523 bytes read in 150 ms (9.8 KiB/s)
uboot_overlays: loading /lib/firmware/MCP2515.dtbo ...
2119 bytes read in 463 ms (3.9 KiB/s)
uboot_overlays: uboot loading of [/lib/firmware/BB-BONE-eMMC1-01-00A0.dtbo] disabled by /boot/uEnv.txt [disable_uboot_overlay_emmc=1]...
uboot_overlays: uboot loading of [/lib/firmware/BB-HDMI-TDA998x-00A0.dtbo] disabled by /boot/uEnv.txt [disable_uboot_overlay_video=1]...
uboot_overlays: uboot loading of [/lib/firmware/BB-ADC-00A0.dtbo] disabled by /boot/uEnv.txt [disable_uboot_overlay_adc=1]...
uboot_overlays: loading /lib/firmware/AM335X-PRU-RPROC-4-14-TI-00A0.dtbo ...
3513 bytes read in 605 ms (4.9 KiB/s)
uboot_overlays: cape universal disabled, external cape enabled or detected...
loading /boot/initrd.img-4.14.78-bone17 ...
4456483 bytes read in 361 ms (11.8 MiB/s)
debug: [console=ttyO0,115200n8 bone_capemgr.uboot_capemgr_enabled=1 root=/dev/mmcblk0p1 ro rootfstype=ext4 rootwait
```

### Kernel
#### 4.14.78-bone17
```
debian@beaglebone:~$ uname -a
Linux beaglebone 4.14.78-bone17 #3 PREEMPT Fri Dec 21 10:18:33 CST 2018 armv7l GNU/Linux
```
* `git clone https://github.com/RobertCNelson/bb-kernel`
* `git checkout am33x-v4.14`
* run the build script `./build_kernel.sh`
* copy kernel image, kernel module tarball and dtb tarball in located in `deploy` to the BeagleBone/PocketBeagle
```
pdp7@sp3:~/dev/bb-kernel$ scp config-4.14.78-bone17 4.14.78-bone17.zImage 4.14.78-bone17-modules.tar.gz  4.14.78-bone17-dtbs.tar.gz debian@192.168.6.2:/tmp

debian@beaglebone:~$ sudo cp 4.14.78-bone17.zImage /boot/vmlinuz-4.14.78-bone17
debian@beaglebone:~$ sudo tar -C / -xzvf ~/4.14.78-bone17-modules.tar.gz
debian@beaglebone:~$ sudo tar -C /boot/dtbs/4.14.78-bone17 -xzvf 4.14.78-bone17-dtbs.tar.gz
```
#### crude method to print debug info
`git diff` of `~/dev/bb-kernel/KERNEL`
```diff
diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
index f3f05fea8e1f..7b8afcdbbbce 100644
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -320,18 +320,26 @@ static int mcp251x_spi_trans(struct spi_device *spi, int len)
 	};
 	struct spi_message m;
 	int ret;
-
+    pr_err("DEBUG SWCAN: mcp251x_spi_trans: spi=%p\n", spi);
+    pr_err("DEBUG SWCAN: mcp251x_spi_trans: len=0x%02x\n", len);
+   	pr_err("DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)\n");
 	spi_message_init(&m);
+    pr_err("DEBUG SWCAN: mcp251x_spi_trans: m=%p\n", &m);
+    pr_err("DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x%02x\n", mcp251x_enable_dma);
 
 	if (mcp251x_enable_dma) {
+    	pr_err("DEBUG SWCAN: mcp251x_spi_trans: t.tx_dma=0x%02x\n", t.tx_dma);
+    	pr_err("DEBUG SWCAN: mcp251x_spi_trans: t.rx_dma=0x%02x\n", t.rx_dma);
 		t.tx_dma = priv->spi_tx_dma;
 		t.rx_dma = priv->spi_rx_dma;
 		m.is_dma_mapped = 1;
 	}
 
+   	pr_err("DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)\n");
 	spi_message_add_tail(&t, &m);
 
 	ret = spi_sync(spi, &m);
+   	pr_err("DEBUG SWCAN: mcp251x_spi_trans: ret=0x%02x\n", ret);
 	if (ret)
 		dev_err(&spi->dev, "spi transfer failed: ret = %d\n", ret);
 	return ret;
@@ -342,11 +350,14 @@ static u8 mcp251x_read_reg(struct spi_device *spi, uint8_t reg)
 	struct mcp251x_priv *priv = spi_get_drvdata(spi);
 	u8 val = 0;
 
+    pr_err("DEBUG SWCAN: mcp251x_read_reg: spi=%p\n", spi);
+    pr_err("DEBUG SWCAN: mcp251x_read_reg: reg=0x%02x\n", reg);
 	priv->spi_tx_buf[0] = INSTRUCTION_READ;
 	priv->spi_tx_buf[1] = reg;
 
 	mcp251x_spi_trans(spi, 3);
 	val = priv->spi_rx_buf[2];
+    pr_err("DEBUG SWCAN: mcp251x_read_reg: val=0x%02x\n", val);
 
 	return val;
 }
@@ -626,14 +637,20 @@ static int mcp251x_setup(struct net_device *net, struct mcp251x_priv *priv,
 
 static int mcp251x_hw_reset(struct spi_device *spi)
 {
-	struct mcp251x_priv *priv = spi_get_drvdata(spi);
+	struct mcp251x_priv *priv;
 	u8 reg;
 	int ret;
 
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): spi=%p\n", spi);
+	priv = spi_get_drvdata(spi);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): priv=%p\n", priv);
+
 	/* Wait for oscillator startup timer after power up */
 	mdelay(MCP251X_OST_DELAY_MS);
 
 	priv->spi_tx_buf[0] = INSTRUCTION_RESET;
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): spriv->spi_tx_buf[0]=0x%02x\n", priv->spi_tx_buf[0]);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_spi_trans(spi, 1)\n");
 	ret = mcp251x_spi_trans(spi, 1);
 	if (ret)
 		return ret;
@@ -641,7 +658,13 @@ static int mcp251x_hw_reset(struct spi_device *spi)
 	/* Wait for oscillator startup timer after reset */
 	mdelay(MCP251X_OST_DELAY_MS);
 	
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): CANSTAT=0x%02x\n", CANSTAT);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_read_reg()\n");
 	reg = mcp251x_read_reg(spi, CANSTAT);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): reg=0x%02x\n", reg);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_MASK=0x%02x\n", CANCTRL_REQOP_MASK);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_CONF=0x%02x\n", CANCTRL_REQOP_CONF);
+    pr_err("DEBUG SWCAN: mcp251x_hw_reset(): (reg & CANCTRL_REQOP_MASK)=0x%02x\n", (reg & CANCTRL_REQOP_MASK));
 	if ((reg & CANCTRL_REQOP_MASK) != CANCTRL_REQOP_CONF)
 		return -ENODEV;
 
@@ -653,12 +676,17 @@ static int mcp251x_hw_probe(struct spi_device *spi)
 	u8 ctrl;
 	int ret;
 
+    pr_err("DEBUG SWCAN: mcp251x_hw_probe: spi=%p\n", spi);
+
 	ret = mcp251x_hw_reset(spi);
+    pr_err("DEBUG SWCAN: mcp251x_hw_probe: ret=%d\n", ret);
 	if (ret)
 		return ret;
 
+    pr_err("DEBUG SWCAN: mcp251x_hw_probe: CANCTRL=0x%02x\n", CANCTRL);
 	ctrl = mcp251x_read_reg(spi, CANCTRL);
-
+    pr_err("DEBUG SWCAN: mcp251x_hw_probe: ctrl=0x%02x\n", ctrl);
+    pr_err("DEBUG SWCAN: mcp251x_hw_probe: ((ctrl & 0x17)=0x%02x\n", (ctrl & 0x17));
 	dev_dbg(&spi->dev, "CANCTRL 0x%02x\n", ctrl);
 
 	/* Check for power up default value */
@@ -1034,14 +1062,41 @@ static int mcp251x_can_probe(struct spi_device *spi)
 	struct clk *clk;
 	int freq, ret;
 
+    printk(KERN_ERR "DEBUG SWCAN: mcp251x_can_probe()\n");
+    pr_err("DEBUG SWCAN: mcp251x_can_probe()\n");
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi=%p\n", spi);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->chip_select=0x%02x\n", spi->chip_select);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->irq=0x%02x\n", spi->irq);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->modalias=%s\n", spi->modalias);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->cs_gpio=0x%02x\n", spi->cs_gpio);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->controller=%p\n", spi->controller);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->controller->bus_num=0x%02x\n", spi->controller->bus_num);
+
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev=%p\n", spi->dev);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->of_node=%p\n", spi->dev.of_node);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->parent=%p\n", spi->dev.parent);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->init_name=%s\n", spi->dev.init_name);
+	if(spi->dev.type != NULL) {
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->type->name=%s\n", spi->dev.type->name);
+	}
+	if(spi->dev.bus != NULL) {
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->name=%s\n", spi->dev.bus->name);
+	    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->dev_name=%s\n", spi->dev.bus->dev_name);
+	    pr_err("DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->dev_root=%s\n", spi->dev.bus->dev_root);
+	}
 	clk = devm_clk_get(&spi->dev, NULL);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): clk=%p\n", clk);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): pdata=%p\n", pdata);
 	if (IS_ERR(clk)) {
 		if (pdata)
 			freq = pdata->oscillator_frequency;
 		else
 			return PTR_ERR(clk);
 	} else {
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): freq = clk_get_rate(clk)\n");
 		freq = clk_get_rate(clk);
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): freq=0x%02x\n", freq);
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): freq=%d\n", freq);
 	}
 
 	/* Sanity check */
@@ -1050,11 +1105,13 @@ static int mcp251x_can_probe(struct spi_device *spi)
 
 	/* Allocate can/net device */
 	net = alloc_candev(sizeof(struct mcp251x_priv), TX_ECHO_SKB_MAX);
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): net=%p\n", net);
 	if (!net)
 		return -ENOMEM;
 
 	if (!IS_ERR(clk)) {
 		ret = clk_prepare_enable(clk);
+    	pr_err("DEBUG SWCAN: mcp251x_can_probe(): ret = clk_prepare_enable(clk): 0x%02x\n", ret);
 		if (ret)
 			goto out_free;
 	}
@@ -1144,6 +1201,7 @@ static int mcp251x_can_probe(struct spi_device *spi)
 	SET_NETDEV_DEV(net, &spi->dev);
 
 	/* Here is OK to not lock the MCP, no one knows about it yet */
+    pr_err("DEBUG SWCAN: mcp251x_can_probe(): call mcp251x_hw_probe()\n");
 	ret = mcp251x_hw_probe(spi);
 	if (ret) {
 		if (ret == -ENODEV)
@@ -1181,6 +1239,9 @@ static int mcp251x_can_remove(struct spi_device *spi)
 	struct mcp251x_priv *priv = spi_get_drvdata(spi);
 	struct net_device *net = priv->net;
 
+    printk(KERN_ERR "DEBUG SWCAN: mcp251x_can_remove\n");
+    pr_err("DEBUG SWCAN: mcp251x_can_remove\n");
+
 	unregister_candev(net);
 
 	mcp251x_power_enable(priv->power, 0);
@@ -1258,7 +1319,7 @@ static struct spi_driver mcp251x_can_driver = {
 };
 module_spi_driver(mcp251x_can_driver);
 
-MODULE_AUTHOR("Chris Elston <celston@katalix.com>, "
-	      "Christian Pellegrin <chripell@evolware.org>");
+MODULE_AUTHOR("TEST TEST TEST, "
+	      "FOO FOO FOO FOO ");
 MODULE_DESCRIPTION("Microchip 251x CAN driver");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 9bf64e6eca9b..ea7d4f16a96f 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -1341,6 +1341,12 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	struct device_node	*node = pdev->dev.of_node;
 	const struct of_device_id *match;
 
+	pr_err("DEBUG SWCAN: omap2_mcspi_probe(): pdev=%p\n", pdev);
+	pr_err("DEBUG SWCAN: omap2_mcspi_probe(): node=%p\n", node);
+	pr_err("DEBUG SWCAN: omap2_mcspi_probe(): node->name=%s\n", node->name);
+	pr_err("DEBUG SWCAN: omap2_mcspi_probe(): node->type=%s\n", node->type);
+	pr_err("DEBUG SWCAN: omap2_mcspi_probe(): node->full_name=%s\n", node->full_name);
+
 	master = spi_alloc_master(&pdev->dev, sizeof *mcspi);
 	if (master == NULL) {
 		dev_dbg(&pdev->dev, "master allocation failed\n");
```
#### related output during boot
```
debian@beaglebone:~$ dmesg |egrep -i '(can|spi)'
[    0.583800] DEBUG SWCAN: omap2_mcspi_probe(): pdev=dc204000
[    0.589564] DEBUG SWCAN: omap2_mcspi_probe(): node=dcb55868
[    0.595211] DEBUG SWCAN: omap2_mcspi_probe(): node->name=spi
[    0.600914] DEBUG SWCAN: omap2_mcspi_probe(): node->type=<NULL>
[    0.606872] DEBUG SWCAN: omap2_mcspi_probe(): node->full_name=/ocp/spi@48030000
[    0.615207] omap2_mcspi 48030000.spi: chipselect 0 already in use
[    0.621428] spi_master spi0: spi_device register error /ocp/spi@48030000/channel@0
[    0.629074] spi_master spi0: Failed to create SPI device for /ocp/spi@48030000/channel@0
[    0.630422] CAN device driver interface
[    0.777127] can: controller area network core (rev 20170425 abi 9)
[   19.139857] DEBUG SWCAN: mcp251x_can_probe()
[   19.406838] DEBUG SWCAN: mcp251x_can_probe()
[   19.544275] DEBUG SWCAN: mcp251x_can_probe(): spi=db56f400
[   19.782634] DEBUG SWCAN: mcp251x_can_probe(): spi->chip_select=0x00
[   19.997762] DEBUG SWCAN: mcp251x_can_probe(): spi->irq=0x3e
[   20.192506] DEBUG SWCAN: mcp251x_can_probe(): spi->modalias=mcp2515
[   20.482613] DEBUG SWCAN: mcp251x_can_probe(): spi->cs_gpio=0xfffffffe
[   20.724291] DEBUG SWCAN: mcp251x_can_probe(): spi->controller=db56e000
[   20.969237] DEBUG SWCAN: mcp251x_can_probe(): spi->controller->bus_num=0x00
[   21.236271] DEBUG SWCAN: mcp251x_can_probe(): spi->dev=db56f578
[   21.544405] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->of_node=dcb55c1c
[   21.756169] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->parent=db56e000
[   22.020346] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->init_name=(null)
[   22.246402] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->name=spi
[   22.398573] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->dev_name=(null)
[   22.528325] DEBUG SWCAN: mcp251x_can_probe(): spi->dev->bus->dev_root=(null)
[   22.764404] DEBUG SWCAN: mcp251x_can_probe(): clk=da9ffdc0
[   22.896335] DEBUG SWCAN: mcp251x_can_probe(): pdata=  (null)
[   23.016319] DEBUG SWCAN: mcp251x_can_probe(): freq = clk_get_rate(clk)
[   23.180345] DEBUG SWCAN: mcp251x_can_probe(): freq=0x7a1200
[   23.324322] DEBUG SWCAN: mcp251x_can_probe(): freq=8000000
[   23.428366] DEBUG SWCAN: mcp251x_can_probe(): net=db035000
[   23.577246] DEBUG SWCAN: mcp251x_can_probe(): ret = clk_prepare_enable(clk): 0x00
[   23.732564] DEBUG SWCAN: mcp251x_can_probe(): call mcp251x_hw_probe()
[   23.921356] DEBUG SWCAN: mcp251x_hw_probe: spi=db56f400
[   24.070978] DEBUG SWCAN: mcp251x_hw_reset(): spi=db56f400
[   24.212109] DEBUG SWCAN: mcp251x_hw_reset(): priv=db0354a0
[   24.574375] DEBUG SWCAN: mcp251x_hw_reset(): spriv->spi_tx_buf[0]=0xc0
[   24.986092] DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_spi_trans(spi, 1)
[   25.224786] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f400
[   25.404450] DEBUG SWCAN: mcp251x_spi_trans: len=0x01
[   25.577669] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[   25.703873] DEBUG SWCAN: mcp251x_spi_trans: m=dc3a9a18
[   25.781107] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[   25.895224] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[   26.003786] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[   26.161376] DEBUG SWCAN: mcp251x_hw_reset(): CANSTAT=0x0e
[   26.249032] DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_read_reg()
[   26.338096] DEBUG SWCAN: mcp251x_read_reg: spi=db56f400
[   26.424309] DEBUG SWCAN: mcp251x_read_reg: reg=0x0e
[   26.533882] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f400
[   26.716317] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[   26.956309] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[   27.184288] DEBUG SWCAN: mcp251x_spi_trans: m=dc3a99f8
[   27.299986] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[   27.422636] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[   27.472426] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[   27.526856] DEBUG SWCAN: mcp251x_read_reg: val=0x80
[   27.584687] DEBUG SWCAN: mcp251x_hw_reset(): reg=0x80
[   27.611370] DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_MASK=0xe0
[   27.640533] DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_CONF=0x80
[   27.675986] DEBUG SWCAN: mcp251x_hw_reset(): (reg & CANCTRL_REQOP_MASK)=0x80
[   27.700828] DEBUG SWCAN: mcp251x_hw_probe: ret=0
[   27.722323] DEBUG SWCAN: mcp251x_hw_probe: CANCTRL=0x0f
[   27.793728] DEBUG SWCAN: mcp251x_read_reg: spi=db56f400
[   27.801947] DEBUG SWCAN: mcp251x_read_reg: reg=0x0f
[   27.808908] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f400
[   27.819537] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[   27.829695] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[   27.840546] DEBUG SWCAN: mcp251x_spi_trans: m=dc3a9a20
[   27.852489] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[   27.861291] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[   27.876376] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[   27.887315] DEBUG SWCAN: mcp251x_read_reg: val=0x87
[   27.894647] DEBUG SWCAN: mcp251x_hw_probe: ctrl=0x87
[   27.906539] DEBUG SWCAN: mcp251x_hw_probe: ((ctrl & 0x17)=0x07
[   27.920619] mcp251x spi0.0: CANCTRL 0x87
[   27.920632] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f400
[   27.933568] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[   27.947507] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[   27.960343] DEBUG SWCAN: mcp251x_spi_trans: m=dc3a9a28
[   27.972333] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[   27.984992] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[   27.993782] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[   28.017187] mcp251x spi0.0 can0: MCP2515 successfully initialized.
```
#### boot without DEBUG SWCAN output:
```
debian@beaglebone:~$ dmesg |egrep -i '(can|spi)' |grep -v SWCAN
[    0.614363] omap2_mcspi 48030000.spi: chipselect 0 already in use
[    0.620587] spi_master spi0: spi_device register error /ocp/spi@48030000/channel@0
[    0.628235] spi_master spi0: Failed to create SPI device for /ocp/spi@48030000/channel@0
[    0.629583] CAN device driver interface
[    0.772846] can: controller area network core (rev 20170425 abi 9)
[   40.501537] mcp251x spi0.0: CANCTRL 0x87
[   40.580953] mcp251x spi0.0 can0: MCP2515 successfully initialized.
```
### Macchina instructions
**[PocketBeagle + M2 + Adapter(BETA)](https://docs.macchina.cc/pb_adapter/)**
* Command:
```
sudo ip link set can0 type can bitrate 500000 listen-only on
sudo ifconfig can0 up
```
* Output:
```
[  398.308395] DEBUG SWCAN: mcp251x_hw_reset(): spi=db56f000
[  398.313948] DEBUG SWCAN: mcp251x_hw_reset(): priv=db19dca0
[  398.326430] DEBUG SWCAN: mcp251x_hw_reset(): spriv->spi_tx_buf[0]=0xc0
[  398.333031] DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_spi_trans(spi, 1)
[  398.341604] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.347879] DEBUG SWCAN: mcp251x_spi_trans: len=0x01
[  398.353783] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.361180] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.367447] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.374658] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.382433] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.393490] DEBUG SWCAN: mcp251x_hw_reset(): CANSTAT=0x0e
[  398.398983] DEBUG SWCAN: mcp251x_hw_reset(): call mcp251x_read_reg()
[  398.406623] DEBUG SWCAN: mcp251x_read_reg: spi=db56f000
[  398.413021] DEBUG SWCAN: mcp251x_read_reg: reg=0x0e
[  398.419154] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.425728] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.431861] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.439086] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dca0
[  398.445573] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.453127] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.461064] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.466991] DEBUG SWCAN: mcp251x_read_reg: val=0x80
[  398.473231] DEBUG SWCAN: mcp251x_hw_reset(): reg=0x80
[  398.479280] DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_MASK=0xe0
[  398.486604] DEBUG SWCAN: mcp251x_hw_reset(): CANCTRL_REQOP_CONF=0x80
[  398.493851] DEBUG SWCAN: mcp251x_hw_reset(): (reg & CANCTRL_REQOP_MASK)=0x80
[  398.501795] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.507978] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.513795] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.520675] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.526665] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.533783] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.541594] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.547634] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.553911] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.559793] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.567203] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.573597] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.581274] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.589295] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.595452] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.601959] DEBUG SWCAN: mcp251x_spi_trans: len=0x04
[  398.608280] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.615300] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.621398] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.628598] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.636313] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.642158] DEBUG SWCAN: mcp251x_read_reg: spi=db56f000
[  398.648558] DEBUG SWCAN: mcp251x_read_reg: reg=0x2a
[  398.654376] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.660631] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.666940] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.673955] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dca0
[  398.680004] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.687182] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.694850] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.700720] DEBUG SWCAN: mcp251x_read_reg: val=0x00
[  398.706462] DEBUG SWCAN: mcp251x_read_reg: spi=db56f000
[  398.712733] DEBUG SWCAN: mcp251x_read_reg: reg=0x29
[  398.718717] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.725170] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.731285] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.738455] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dca0
[  398.744922] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.752612] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.760653] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.766578] DEBUG SWCAN: mcp251x_read_reg: val=0x91
[  398.772830] DEBUG SWCAN: mcp251x_read_reg: spi=db56f000
[  398.779031] DEBUG SWCAN: mcp251x_read_reg: reg=0x28
[  398.784881] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.791090] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.796982] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.804014] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dca0
[  398.810116] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.817285] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.824987] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.830844] DEBUG SWCAN: mcp251x_read_reg: val=0x01
[  398.836681] mcp251x spi0.0: CNF: 0x00 0x91 0x01
[  398.836691] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.844573] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.850563] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.857816] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.863933] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.871654] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.879869] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.886036] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.892646] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.898856] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.906098] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc0
[  398.912481] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.919983] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.927752] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.933629] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.939806] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.945642] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.952561] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc8
[  398.958712] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  398.965897] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  398.974020] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
[  398.980023] DEBUG SWCAN: mcp251x_spi_trans: spi=db56f000
[  398.986259] DEBUG SWCAN: mcp251x_spi_trans: len=0x03
[  398.992181] DEBUG SWCAN: mcp251x_spi_trans: spi_message_init(&m)
[  398.999035] DEBUG SWCAN: mcp251x_spi_trans: m=dc15dcc8
[  399.005079] DEBUG SWCAN: mcp251x_spi_trans: mcp251x_enable_dma=0x00
[  399.012370] DEBUG SWCAN: mcp251x_spi_trans: spi_message_add_tail(&t, &m)
[  399.020403] DEBUG SWCAN: mcp251x_spi_trans: ret=0x00
```
* Command:
```
candump -cae can0,0:0,#FFFFFFFF
```
* Output:
```
[  451.428585] can: raw protocol (rev 20170425)
```
* ifconfig
```
debian@beaglebone:~$ ifconfig can0
can0: flags=193<UP,RUNNING,NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
```