can: mcp25xxfd: add regmap infrastructure

This patch adds the regmap infrastructure for the Microchip MCP25xxFD SPI CAN
controller family. The actual driver is added in the next commit.
Tested-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20200918172536.2074504-3-mkl@pengutronix.de

drivers/net/can/spi/Kconfig

@@ -13,4 +13,6 @@ config CAN_MCP251X
 	  Driver for the Microchip MCP251x and MCP25625 SPI CAN
 	  controllers.
 
+source "drivers/net/can/spi/mcp25xxfd/Kconfig"
+
 endmenu

drivers/net/can/spi/Makefile

@@ -6,3 +6,4 @@
 
 obj-$(CONFIG_CAN_HI311X)	+= hi311x.o
 obj-$(CONFIG_CAN_MCP251X)	+= mcp251x.o
+obj-y				+= mcp25xxfd/

drivers/net/can/spi/mcp25xxfd/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+
+config CAN_MCP25XXFD
+	tristate "Microchip MCP25xxFD SPI CAN controllers"
+	select REGMAP
+	help
+	  Driver for the Microchip MCP25XXFD SPI FD-CAN controller
+	  family.
+
+config CAN_MCP25XXFD_SANITY
+	depends on CAN_MCP25XXFD
+	bool "Additional Sanity Checks"
+	help
+	  This option enables additional sanity checks in the driver,
+	  that compares various internal counters with the in chip
+	  variants. This comes with a runtime overhead.
+	  Disable if unsure.

drivers/net/can/spi/mcp25xxfd/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_CAN_MCP25XXFD) += mcp25xxfd.o
+
+mcp25xxfd-objs :=
+mcp25xxfd-objs += mcp25xxfd-crc16.o
+mcp25xxfd-objs += mcp25xxfd-regmap.o

drivers/net/can/spi/mcp25xxfd/mcp25xxfd-crc16.c

+// SPDX-License-Identifier: GPL-2.0
+//
+// mcp25xxfd - Microchip MCP25xxFD Family CAN controller driver
+//
+// Copyright (c) 2020 Pengutronix,
+//                    Marc Kleine-Budde <kernel@pengutronix.de>
+//
+// Based on:
+//
+// CAN bus driver for Microchip 25XXFD CAN Controller with SPI Interface
+//
+// Copyright (c) 2019 Martin Sperl <kernel@martin.sperl.org>
+//
+
+#include "mcp25xxfd.h"
+
+/* The standard crc16 in linux/crc16.h is unfortunately not computing
+ * the correct results (left shift vs. right shift). So here an
+ * implementation with a table generated with the help of:
+ *
+ * http://lkml.iu.edu/hypermail/linux/kernel/0508.1/1085.html
+ */
+static const u16 mcp25xxfd_crc16_table[] = {
+	0x0000, 0x8005, 0x800f, 0x000a, 0x801b, 0x001e, 0x0014, 0x8011,
+	0x8033, 0x0036, 0x003c, 0x8039, 0x0028, 0x802d, 0x8027, 0x0022,
+	0x8063, 0x0066, 0x006c, 0x8069, 0x0078, 0x807d, 0x8077, 0x0072,
+	0x0050, 0x8055, 0x805f, 0x005a, 0x804b, 0x004e, 0x0044, 0x8041,
+	0x80c3, 0x00c6, 0x00cc, 0x80c9, 0x00d8, 0x80dd, 0x80d7, 0x00d2,
+	0x00f0, 0x80f5, 0x80ff, 0x00fa, 0x80eb, 0x00ee, 0x00e4, 0x80e1,
+	0x00a0, 0x80a5, 0x80af, 0x00aa, 0x80bb, 0x00be, 0x00b4, 0x80b1,
+	0x8093, 0x0096, 0x009c, 0x8099, 0x0088, 0x808d, 0x8087, 0x0082,
+	0x8183, 0x0186, 0x018c, 0x8189, 0x0198, 0x819d, 0x8197, 0x0192,
+	0x01b0, 0x81b5, 0x81bf, 0x01ba, 0x81ab, 0x01ae, 0x01a4, 0x81a1,
+	0x01e0, 0x81e5, 0x81ef, 0x01ea, 0x81fb, 0x01fe, 0x01f4, 0x81f1,
+	0x81d3, 0x01d6, 0x01dc, 0x81d9, 0x01c8, 0x81cd, 0x81c7, 0x01c2,
+	0x0140, 0x8145, 0x814f, 0x014a, 0x815b, 0x015e, 0x0154, 0x8151,
+	0x8173, 0x0176, 0x017c, 0x8179, 0x0168, 0x816d, 0x8167, 0x0162,
+	0x8123, 0x0126, 0x012c, 0x8129, 0x0138, 0x813d, 0x8137, 0x0132,
+	0x0110, 0x8115, 0x811f, 0x011a, 0x810b, 0x010e, 0x0104, 0x8101,
+	0x8303, 0x0306, 0x030c, 0x8309, 0x0318, 0x831d, 0x8317, 0x0312,
+	0x0330, 0x8335, 0x833f, 0x033a, 0x832b, 0x032e, 0x0324, 0x8321,
+	0x0360, 0x8365, 0x836f, 0x036a, 0x837b, 0x037e, 0x0374, 0x8371,
+	0x8353, 0x0356, 0x035c, 0x8359, 0x0348, 0x834d, 0x8347, 0x0342,
+	0x03c0, 0x83c5, 0x83cf, 0x03ca, 0x83db, 0x03de, 0x03d4, 0x83d1,
+	0x83f3, 0x03f6, 0x03fc, 0x83f9, 0x03e8, 0x83ed, 0x83e7, 0x03e2,
+	0x83a3, 0x03a6, 0x03ac, 0x83a9, 0x03b8, 0x83bd, 0x83b7, 0x03b2,
+	0x0390, 0x8395, 0x839f, 0x039a, 0x838b, 0x038e, 0x0384, 0x8381,
+	0x0280, 0x8285, 0x828f, 0x028a, 0x829b, 0x029e, 0x0294, 0x8291,
+	0x82b3, 0x02b6, 0x02bc, 0x82b9, 0x02a8, 0x82ad, 0x82a7, 0x02a2,
+	0x82e3, 0x02e6, 0x02ec, 0x82e9, 0x02f8, 0x82fd, 0x82f7, 0x02f2,
+	0x02d0, 0x82d5, 0x82df, 0x02da, 0x82cb, 0x02ce, 0x02c4, 0x82c1,
+	0x8243, 0x0246, 0x024c, 0x8249, 0x0258, 0x825d, 0x8257, 0x0252,
+	0x0270, 0x8275, 0x827f, 0x027a, 0x826b, 0x026e, 0x0264, 0x8261,
+	0x0220, 0x8225, 0x822f, 0x022a, 0x823b, 0x023e, 0x0234, 0x8231,
+	0x8213, 0x0216, 0x021c, 0x8219, 0x0208, 0x820d, 0x8207, 0x0202
+};
+
+static inline u16 mcp25xxfd_crc16_byte(u16 crc, const u8 data)
+{
+	u8 index = (crc >> 8) ^ data;
+
+	return (crc << 8) ^ mcp25xxfd_crc16_table[index];
+}
+
+static u16 mcp25xxfd_crc16(u16 crc, u8 const *buffer, size_t len)
+{
+	while (len--)
+		crc = mcp25xxfd_crc16_byte(crc, *buffer++);
+
+	return crc;
+}
+
+u16 mcp25xxfd_crc16_compute(const void *data, size_t data_size)
+{
+	u16 crc = 0xffff;
+
+	return mcp25xxfd_crc16(crc, data, data_size);
+}
+
+u16 mcp25xxfd_crc16_compute2(const void *cmd, size_t cmd_size,
+			     const void *data, size_t data_size)
+{
+	u16 crc;
+
+	crc = mcp25xxfd_crc16_compute(cmd, cmd_size);
+	crc = mcp25xxfd_crc16(crc, data, data_size);
+
+	return crc;
+}