FROMLIST: can: Add Loongson CAN-FD controller driver

Add support for the CAN-FD controller integrated into Loongson-2K series
SoCs. The controller supports both Classic CAN and CAN FD, with up to 8
transmit buffers, hardware timestamping, error counters, and various
control modes (loopback, listen-only, one-shot, non-ISO FD, etc.).

The driver implements:
- NAPI for RX path
- TX buffer management with echo skb support
- Bus error reporting and fault confinement state handling
- Bit timing configuration for nominal and data phase
- Secondary Sample Point (SSP) configuration for high bitrates

Co-developed-by: Bingxiong Li <libingxiong@loongson.cn>
Signed-off-by: Bingxiong Li <libingxiong@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>

Link: https://lore.kernel.org/loongarch/cover.1782787997.git.zhoubinbin@loongson.cn/
Signed-off-by: Mingcong Bai <jeffbai@aosc.io>

Author: AaronDot

MAINTAINERS

@@ -15077,6 +15077,13 @@ F:	arch/loongarch/
 F:	drivers/*/*loongarch*
 F:	drivers/cpufreq/loongson3_cpufreq.c
 
+LOONGSON CAN FD DRIVER
+M:	Bingxiong Li <libingxiong@loongson.cn>
+M:	Binbin Zhou <zhoubinbin@loongson.cn>
+L:	linux-can@vger.kernel.org
+S:	Maintained
+F:	drivers/net/can/loongson_canfd/
+
 LOONGSON GPIO DRIVER
 M:	Yinbo Zhu <zhuyinbo@loongson.cn>
 L:	linux-gpio@vger.kernel.org

drivers/net/can/Kconfig

@@ -189,6 +189,17 @@ config CAN_KVASER_PCIEFD
 	    Kvaser M.2 PCIe 4xCAN
 	    Kvaser PCIe 8xCAN
 
+config CAN_LOONGSON_CANFD
+	tristate "Loongson CAN-FD controller"
+	depends on HAS_IOMEM
+	select REGMAP_MMIO
+	help
+	  This is a canfd driver switch for the Loongson platform,
+	  integrated with the Loongson-2K series SoCs.
+
+	  To compile as a module, choose M here: the module will be
+	  called loongson_canfd.
+
 config CAN_SLCAN
 	tristate "Serial / USB serial CAN Adaptors (slcan)"
 	depends on TTY

drivers/net/can/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_CAN_GRCAN)		+= grcan.o
 obj-$(CONFIG_CAN_IFI_CANFD)	+= ifi_canfd/
 obj-$(CONFIG_CAN_JANZ_ICAN3)	+= janz-ican3.o
 obj-$(CONFIG_CAN_KVASER_PCIEFD)	+= kvaser_pciefd/
+obj-$(CONFIG_CAN_LOONGSON_CANFD)	+= loongson_canfd.o
 obj-$(CONFIG_CAN_MSCAN)		+= mscan/
 obj-$(CONFIG_CAN_M_CAN)		+= m_can/
 obj-$(CONFIG_CAN_PEAK_PCIEFD)	+= peak_canfd/