fpga: dfl: add support for N3000 Nios private feature

This patch adds support for the Nios handshake private feature on Intel
PAC (Programmable Acceleration Card) N3000.

The Nios is the embedded processor on the FPGA card. This private feature
provides a handshake interface to FPGA Nios firmware, which receives
retimer configuration command from host and executes via an internal SPI
master (spi-altera). When Nios finishes the configuration, host takes over
the ownership of the SPI master to control an Intel MAX10 BMC (Board
Management Controller) Chip on the SPI bus.

For Nios firmware handshake part, this driver requests the retimer
configuration for Nios firmware on probe, and adds some sysfs nodes for
user to query the onboard retimer's working mode and Nios firmware
version.

For SPI part, this driver adds a spi-altera platform device as well as
the MAX10 BMC spi slave info. A spi-altera driver will be matched to
handle the following SPI work.

[[email protected]: Fixed up ABI doc kernel release]

Reviewed-by: Tom Rix <[email protected]>
Signed-off-by: Xu Yilun <[email protected]>
Signed-off-by: Wu Hao <[email protected]>
Signed-off-by: Matthew Gerlach <[email protected]>
Signed-off-by: Russ Weight <[email protected]>
Signed-off-by: YueHaibing <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Documentation/ABI/testing/sysfs-bus-dfl-devices-n3000-nios

@@ -0,0 +1,47 @@
+What:		/sys/bus/dfl/devices/dfl_dev.X/fec_mode
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <[email protected]>
+Description:	Read-only. Returns the FEC mode of the 25G links of the
+		ethernet retimers configured by Nios firmware. "rs" for Reed
+		Solomon FEC, "kr" for Fire Code FEC, "no" for NO FEC.
+		"not supported" if the FEC mode setting is not supported, this
+		happens when the Nios firmware version major < 3, or no link is
+		configured to 25G.
+		Format: string
+
+What:		/sys/bus/dfl/devices/dfl_dev.X/retimer_A_mode
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <[email protected]>
+Description:	Read-only. Returns the enumeration value of the working mode of
+		the retimer A configured by the Nios firmware. The value is
+		read out from shared registers filled by the Nios firmware. Now
+		the values could be:
+
+		- "0": Reset
+		- "1": 4x10G
+		- "2": 4x25G
+		- "3": 2x25G
+		- "4": 2x25G+2x10G
+		- "5": 1x25G
+
+		If the Nios firmware is updated in future to support more
+		retimer modes, more enumeration value is expected.
+		Format: 0x%x
+
+What:		/sys/bus/dfl/devices/dfl_dev.X/retimer_B_mode
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <[email protected]>
+Description:	Read-only. Returns the enumeration value of the working mode of
+		the retimer B configured by the Nios firmware. The value format
+		is the same as retimer_A_mode.
+
+What:		/sys/bus/dfl/devices/dfl_dev.X/nios_fw_version
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <[email protected]>
+Description:	Read-only. Returns the version of the Nios firmware in the
+		FPGA. Its format is "major.minor.patch".
+		Format: %x.%x.%x

MAINTAINERS

@@ -6954,7 +6954,7 @@ M:	Wu Hao <[email protected]>
 R:	Tom Rix <[email protected]>
 L:	[email protected]
 S:	Maintained
-F:	Documentation/ABI/testing/sysfs-bus-dfl
+F:	Documentation/ABI/testing/sysfs-bus-dfl*
 F:	Documentation/fpga/dfl.rst
 F:	drivers/fpga/dfl*
 F:	include/linux/dfl.h

drivers/fpga/Kconfig

@@ -192,6 +192,17 @@ config FPGA_DFL_AFU
 	  to the FPGA infrastructure via a Port. There may be more than one
 	  Port/AFU per DFL based FPGA device.
 
+config FPGA_DFL_NIOS_INTEL_PAC_N3000
+	tristate "FPGA DFL NIOS Driver for Intel PAC N3000"
+	depends on FPGA_DFL
+	select REGMAP
+	help
+	  This is the driver for the N3000 Nios private feature on Intel
+	  PAC (Programmable Acceleration Card) N3000. It communicates
+	  with the embedded Nios processor to configure the retimers on
+	  the card. It also instantiates the SPI master (spi-altera) for
+	  the card's BMC (Board Management Controller).
+
 config FPGA_DFL_PCI
 	tristate "FPGA DFL PCIe Device Driver"
 	depends on PCI && FPGA_DFL

drivers/fpga/Makefile

@@ -44,5 +44,7 @@ dfl-fme-objs += dfl-fme-perf.o
 dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
 dfl-afu-objs += dfl-afu-error.o
 
+obj-$(CONFIG_FPGA_DFL_NIOS_INTEL_PAC_N3000)	+= dfl-n3000-nios.o
+
 # Drivers for FPGAs which implement DFL
 obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o