OpenRISC updates for 5.11

This series adds:
 
  * New drivers and OpenRISC support for the LiteX platform
  * A bug fix to support userspace gdb debugging
  * Fixes one compile issue with blk-iocost
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Merge tag 'for-linus' of git://github.com/openrisc/linux

Pull OpenRISC updates from Stafford Horne:

 - New drivers and OpenRISC support for the LiteX platform

 - A bug fix to support userspace gdb debugging

 - Fixes one compile issue with blk-iocost

* tag 'for-linus' of git://github.com/openrisc/linux:
  openrisc: add local64.h to fix blk-iocost build
  openrisc: fix trap for debugger breakpoint signalling
  openrisc: add support for LiteX
  drivers/tty/serial: add LiteUART driver
  dt-bindings: serial: document LiteUART bindings
  drivers/soc/litex: add LiteX SoC Controller driver
  dt-bindings: soc: document LiteX SoC Controller bindings
  dt-bindings: vendor: add vendor prefix for LiteX

Documentation/devicetree/bindings/serial/litex,liteuart.yaml

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/litex,liteuart.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: LiteUART serial controller
+
+maintainers:
+  - Karol Gugala <kgugala@antmicro.com>
+  - Mateusz Holenko <mholenko@antmicro.com>
+
+description: |
+  LiteUART serial controller is a part of the LiteX FPGA SoC builder. It supports
+  multiple CPU architectures, currently including e.g. OpenRISC and RISC-V.
+
+properties:
+  compatible:
+    const: litex,liteuart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    uart0: serial@e0001800 {
+      compatible = "litex,liteuart";
+      reg = <0xe0001800 0x100>;
+      interrupts = <2>;
+    };

Documentation/devicetree/bindings/soc/litex/litex,soc-controller.yaml

@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+# Copyright 2020 Antmicro <www.antmicro.com>
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/soc/litex/litex,soc-controller.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: LiteX SoC Controller driver
+
+description: |
+  This is the SoC Controller driver for the LiteX SoC Builder.
+  Its purpose is to verify LiteX CSR (Control&Status Register) access
+  operations and provide functions for other drivers to read/write CSRs
+  and to check if those accessors are ready to be used.
+
+maintainers:
+  - Karol Gugala <kgugala@antmicro.com>
+  - Mateusz Holenko <mholenko@antmicro.com>
+
+properties:
+  compatible:
+    const: litex,soc-controller
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    soc_ctrl0: soc-controller@f0000000 {
+        compatible = "litex,soc-controller";
+        reg = <0xf0000000 0xc>;
+        status = "okay";
+    };
+
+...

Documentation/devicetree/bindings/vendor-prefixes.yaml

@@ -621,6 +621,8 @@ patternProperties:
     description: Linux-specific binding
   "^linx,.*":
     description: Linx Technologies
+  "^litex,.*":
+    description: LiteX SoC builder
   "^lltc,.*":
     description: Linear Technology Corporation
   "^logicpd,.*":

MAINTAINERS

@@ -10264,6 +10264,16 @@ L:	kunit-dev@googlegroups.com
 S:	Maintained
 F:	lib/list-test.c
 
+LITEX PLATFORM
+M:	Karol Gugala <kgugala@antmicro.com>
+M:	Mateusz Holenko <mholenko@antmicro.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/*/litex,*.yaml
+F:	arch/openrisc/boot/dts/or1klitex.dts
+F:	drivers/soc/litex/litex_soc_ctrl.c
+F:	drivers/tty/serial/liteuart.c
+F:	include/linux/litex.h
+
 LIVE PATCHING
 M:	Josh Poimboeuf <jpoimboe@redhat.com>
 M:	Jiri Kosina <jikos@kernel.org>

arch/openrisc/boot/dts/or1klitex.dts

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LiteX-based System on Chip
+ *
+ * Copyright (C) 2019 Antmicro <www.antmicro.com>
+ */
+
+/dts-v1/;
+/ {
+	compatible = "opencores,or1ksim";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	interrupt-parent = <&pic>;
+
+	aliases {
+		serial0 = &serial0;
+	};
+
+	chosen {
+		bootargs = "console=liteuart";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x10000000>;
+	};
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		cpu@0 {
+			compatible = "opencores,or1200-rtlsvn481";
+			reg = <0>;
+			clock-frequency = <100000000>;
+		};
+	};
+
+	pic: pic {
+		compatible = "opencores,or1k-pic";
+		#interrupt-cells = <1>;
+		interrupt-controller;
+	};
+
+	serial0: serial@e0002000 {
+		device_type = "serial";
+		compatible = "litex,liteuart";
+		reg = <0xe0002000 0x100>;
+	};
+
+	soc_ctrl0: soc_controller@e0000000 {
+			compatible = "litex,soc-controller";
+			reg = <0xe0000000 0xc>;
+			status = "okay";
+	};
+};

arch/openrisc/configs/or1klitex_defconfig

@@ -0,0 +1,18 @@
+CONFIG_BLK_DEV_INITRD=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BUG_ON_DATA_CORRUPTION=y
+CONFIG_CC_OPTIMIZE_FOR_SIZE=y
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
+CONFIG_EMBEDDED=y
+CONFIG_HZ_100=y
+CONFIG_INITRAMFS_SOURCE="openrisc-rootfs.cpio.gz"
+CONFIG_OF_OVERLAY=y
+CONFIG_OPENRISC_BUILTIN_DTB="or1klitex"
+CONFIG_PANIC_ON_OOPS=y
+CONFIG_PRINTK_TIME=y
+CONFIG_LITEX_SOC_CONTROLLER=y
+CONFIG_SERIAL_LITEUART=y
+CONFIG_SERIAL_LITEUART_CONSOLE=y
+CONFIG_SOFTLOCKUP_DETECTOR=y
+CONFIG_TTY_PRINTK=y

arch/openrisc/include/asm/Kbuild

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 generic-y += extable.h
 generic-y += kvm_para.h
+generic-y += local64.h
 generic-y += mcs_spinlock.h
 generic-y += qspinlock_types.h
 generic-y += qspinlock.h

arch/openrisc/kernel/traps.c

@@ -238,9 +238,7 @@ void __init trap_init(void)
 
 asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
 {
-	force_sig_fault(SIGTRAP, TRAP_TRACE, (void __user *)address);
-
-	regs->pc += 4;
+	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
 }
 
 asmlinkage void do_unaligned_access(struct pt_regs *regs, unsigned long address)

drivers/soc/Kconfig

@@ -9,6 +9,7 @@ source "drivers/soc/bcm/Kconfig"
 source "drivers/soc/fsl/Kconfig"
 source "drivers/soc/imx/Kconfig"
 source "drivers/soc/ixp4xx/Kconfig"
+source "drivers/soc/litex/Kconfig"
 source "drivers/soc/mediatek/Kconfig"
 source "drivers/soc/qcom/Kconfig"
 source "drivers/soc/renesas/Kconfig"

drivers/soc/Makefile

@@ -14,6 +14,7 @@ obj-$(CONFIG_ARCH_GEMINI)	+= gemini/
 obj-y				+= imx/
 obj-$(CONFIG_ARCH_IXP4XX)	+= ixp4xx/
 obj-$(CONFIG_SOC_XWAY)		+= lantiq/
+obj-$(CONFIG_LITEX_SOC_CONTROLLER) += litex/
 obj-y				+= mediatek/
 obj-y				+= amlogic/
 obj-y				+= qcom/

drivers/soc/litex/Kconfig

@@ -0,0 +1,19 @@
+# SPDX-License_Identifier: GPL-2.0
+
+menu "Enable LiteX SoC Builder specific drivers"
+
+config LITEX
+	bool
+
+config LITEX_SOC_CONTROLLER
+	tristate "Enable LiteX SoC Controller driver"
+	depends on OF || COMPILE_TEST
+	select LITEX
+	help
+	  This option enables the SoC Controller Driver which verifies
+	  LiteX CSR access and provides common litex_get_reg/litex_set_reg
+	  accessors.
+	  All drivers that use functions from litex.h must depend on
+	  LITEX.
+
+endmenu

drivers/soc/litex/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License_Identifier: GPL-2.0
+
+obj-$(CONFIG_LITEX_SOC_CONTROLLER)	+= litex_soc_ctrl.o

drivers/soc/litex/litex_soc_ctrl.c

@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LiteX SoC Controller Driver
+ *
+ * Copyright (C) 2020 Antmicro <www.antmicro.com>
+ *
+ */
+
+#include <linux/litex.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+
+/*
+ * LiteX SoC Generator, depending on the configuration, can split a single
+ * logical CSR (Control&Status Register) into a series of consecutive physical
+ * registers.
+ *
+ * For example, in the configuration with 8-bit CSR Bus, 32-bit aligned (the
+ * default one for 32-bit CPUs) a 32-bit logical CSR will be generated as four
+ * 32-bit physical registers, each one containing one byte of meaningful data.
+ *
+ * For details see: https://github.com/enjoy-digital/litex/wiki/CSR-Bus
+ *
+ * The purpose of `litex_set_reg`/`litex_get_reg` is to implement the logic
+ * of writing to/reading from the LiteX CSR in a single place that can be
+ * then reused by all LiteX drivers.
+ */
+
+/**
+ * litex_set_reg() - Writes the value to the LiteX CSR (Control&Status Register)
+ * @reg: Address of the CSR
+ * @reg_size: The width of the CSR expressed in the number of bytes
+ * @val: Value to be written to the CSR
+ *
+ * In the currently supported LiteX configuration (8-bit CSR Bus, 32-bit aligned),
+ * a 32-bit LiteX CSR is generated as 4 consecutive 32-bit physical registers,
+ * each one containing one byte of meaningful data.
+ *
+ * This function splits a single possibly multi-byte write into a series of
+ * single-byte writes with a proper offset.
+ */
+void litex_set_reg(void __iomem *reg, unsigned long reg_size,
+		    unsigned long val)
+{
+	unsigned long shifted_data, shift, i;
+
+	for (i = 0; i < reg_size; ++i) {
+		shift = ((reg_size - i - 1) * LITEX_SUBREG_SIZE_BIT);
+		shifted_data = val >> shift;
+
+		WRITE_LITEX_SUBREGISTER(shifted_data, reg, i);
+	}
+}
+EXPORT_SYMBOL_GPL(litex_set_reg);
+
+/**
+ * litex_get_reg() - Reads the value of the LiteX CSR (Control&Status Register)
+ * @reg: Address of the CSR
+ * @reg_size: The width of the CSR expressed in the number of bytes
+ *
+ * Return: Value read from the CSR
+ *
+ * In the currently supported LiteX configuration (8-bit CSR Bus, 32-bit aligned),
+ * a 32-bit LiteX CSR is generated as 4 consecutive 32-bit physical registers,
+ * each one containing one byte of meaningful data.
+ *
+ * This function generates a series of single-byte reads with a proper offset
+ * and joins their results into a single multi-byte value.
+ */
+unsigned long litex_get_reg(void __iomem *reg, unsigned long reg_size)
+{
+	unsigned long shifted_data, shift, i;
+	unsigned long result = 0;
+
+	for (i = 0; i < reg_size; ++i) {
+		shifted_data = READ_LITEX_SUBREGISTER(reg, i);
+
+		shift = ((reg_size - i - 1) * LITEX_SUBREG_SIZE_BIT);
+		result |= (shifted_data << shift);
+	}
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(litex_get_reg);
+
+#define SCRATCH_REG_OFF         0x04
+#define SCRATCH_REG_VALUE       0x12345678
+#define SCRATCH_TEST_VALUE      0xdeadbeef
+
+/*
+ * Check LiteX CSR read/write access
+ *
+ * This function reads and writes a scratch register in order to verify if CSR
+ * access works.
+ *
+ * In case any problems are detected, the driver should panic.
+ *
+ * Access to the LiteX CSR is, by design, done in CPU native endianness.
+ * The driver should not dynamically configure access functions when
+ * the endianness mismatch is detected. Such situation indicates problems in
+ * the soft SoC design and should be solved at the LiteX generator level,
+ * not in the software.
+ */
+static int litex_check_csr_access(void __iomem *reg_addr)
+{
+	unsigned long reg;
+
+	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
+
+	if (reg != SCRATCH_REG_VALUE) {
+		panic("Scratch register read error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
+			SCRATCH_REG_VALUE, reg);
+		return -EINVAL;
+	}
+
+	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
+	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
+
+	if (reg != SCRATCH_TEST_VALUE) {
+		panic("Scratch register write error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
+			SCRATCH_TEST_VALUE, reg);
+		return -EINVAL;
+	}
+
+	/* restore original value of the SCRATCH register */
+	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
+
+	pr_info("LiteX SoC Controller driver initialized");
+
+	return 0;
+}
+
+struct litex_soc_ctrl_device {
+	void __iomem *base;
+};
+
+static const struct of_device_id litex_soc_ctrl_of_match[] = {
+	{.compatible = "litex,soc-controller"},
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
+
+static int litex_soc_ctrl_probe(struct platform_device *pdev)
+{
+	struct litex_soc_ctrl_device *soc_ctrl_dev;
+
+	soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
+	if (!soc_ctrl_dev)
+		return -ENOMEM;
+
+	soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(soc_ctrl_dev->base))
+		return PTR_ERR(soc_ctrl_dev->base);
+
+	return litex_check_csr_access(soc_ctrl_dev->base);
+}
+
+static struct platform_driver litex_soc_ctrl_driver = {
+	.driver = {
+		.name = "litex-soc-controller",
+		.of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
+	},
+	.probe = litex_soc_ctrl_probe,
+};
+
+module_platform_driver(litex_soc_ctrl_driver);
+MODULE_DESCRIPTION("LiteX SoC Controller driver");
+MODULE_AUTHOR("Antmicro <www.antmicro.com>");
+MODULE_LICENSE("GPL v2");

drivers/tty/serial/Kconfig

@@ -1567,6 +1567,38 @@ config SERIAL_MILBEAUT_USIO_CONSOLE
 	  receives all kernel messages and warnings and which allows logins in
 	  single user mode).
 
+config SERIAL_LITEUART
+	tristate "LiteUART serial port support"
+	depends on HAS_IOMEM
+	depends on OF || COMPILE_TEST
+	depends on LITEX
+	select SERIAL_CORE
+	help
+	  This driver is for the FPGA-based LiteUART serial controller from LiteX
+	  SoC builder.
+
+	  Say 'Y' or 'M' here if you wish to use the LiteUART serial controller.
+	  Otherwise, say 'N'.
+
+config SERIAL_LITEUART_MAX_PORTS
+	int "Maximum number of LiteUART ports"
+	depends on SERIAL_LITEUART
+	default "1"
+	help
+	  Set this to the maximum number of serial ports you want the driver
+	  to support.
+
+config SERIAL_LITEUART_CONSOLE
+	bool "LiteUART serial port console support"
+	depends on SERIAL_LITEUART=y
+	select SERIAL_CORE_CONSOLE
+	help
+	  Say 'Y' or 'M' here if you wish to use the FPGA-based LiteUART serial
+	  controller from LiteX SoC builder as the system console
+	  (the system console is the device which receives all kernel messages
+	  and warnings and which allows logins in single user mode).
+	  Otherwise, say 'N'.
+
 endmenu
 
 config SERIAL_MCTRL_GPIO

drivers/tty/serial/Makefile

@@ -89,6 +89,7 @@ obj-$(CONFIG_SERIAL_OWL)	+= owl-uart.o
 obj-$(CONFIG_SERIAL_RDA)	+= rda-uart.o
 obj-$(CONFIG_SERIAL_MILBEAUT_USIO) += milbeaut_usio.o
 obj-$(CONFIG_SERIAL_SIFIVE)	+= sifive.o
+obj-$(CONFIG_SERIAL_LITEUART) += liteuart.o
 
 # GPIOLIB helpers for modem control lines
 obj-$(CONFIG_SERIAL_MCTRL_GPIO)	+= serial_mctrl_gpio.o

drivers/tty/serial/liteuart.c

@@ -0,0 +1,404 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LiteUART serial controller (LiteX) Driver
+ *
+ * Copyright (C) 2019-2020 Antmicro <www.antmicro.com>
+ */
+
+#include <linux/console.h>
+#include <linux/litex.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/tty_flip.h>
+#include <linux/xarray.h>
+
+/*
+ * CSRs definitions (base address offsets + width)
+ *
+ * The definitions below are true for LiteX SoC configured for 8-bit CSR Bus,
+ * 32-bit aligned.
+ *
+ * Supporting other configurations might require new definitions or a more
+ * generic way of indexing the LiteX CSRs.
+ *
+ * For more details on how CSRs are defined and handled in LiteX, see comments
+ * in the LiteX SoC Driver: drivers/soc/litex/litex_soc_ctrl.c
+ */
+#define OFF_RXTX	0x00
+#define OFF_TXFULL	0x04
+#define OFF_RXEMPTY	0x08
+#define OFF_EV_STATUS	0x0c
+#define OFF_EV_PENDING	0x10
+#define OFF_EV_ENABLE	0x14
+
+/* events */
+#define EV_TX		0x1
+#define EV_RX		0x2
+
+struct liteuart_port {
+	struct uart_port port;
+	struct timer_list timer;
+	u32 id;
+};
+
+#define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
+
+static DEFINE_XARRAY_FLAGS(liteuart_array, XA_FLAGS_ALLOC);
+
+#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
+static struct console liteuart_console;
+#endif
+
+static struct uart_driver liteuart_driver = {
+	.owner = THIS_MODULE,
+	.driver_name = "liteuart",
+	.dev_name = "ttyLXU",
+	.major = 0,
+	.minor = 0,
+	.nr = CONFIG_SERIAL_LITEUART_MAX_PORTS,
+#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
+	.cons = &liteuart_console,
+#endif
+};
+
+static void liteuart_timer(struct timer_list *t)
+{
+	struct liteuart_port *uart = from_timer(uart, t, timer);
+	struct uart_port *port = &uart->port;
+	unsigned char __iomem *membase = port->membase;
+	unsigned int flg = TTY_NORMAL;
+	int ch;
+	unsigned long status;
+
+	while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
+		ch = litex_read8(membase + OFF_RXTX);
+		port->icount.rx++;
+
+		/* necessary for RXEMPTY to refresh its value */
+		litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
+
+		/* no overflow bits in status */
+		if (!(uart_handle_sysrq_char(port, ch)))
+			uart_insert_char(port, status, 0, ch, flg);
+
+		tty_flip_buffer_push(&port->state->port);
+	}
+
+	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+}
+
+static void liteuart_putchar(struct uart_port *port, int ch)
+{
+	while (litex_read8(port->membase + OFF_TXFULL))
+		cpu_relax();
+
+	litex_write8(port->membase + OFF_RXTX, ch);
+}
+
+static unsigned int liteuart_tx_empty(struct uart_port *port)
+{
+	/* not really tx empty, just checking if tx is not full */
+	if (!litex_read8(port->membase + OFF_TXFULL))
+		return TIOCSER_TEMT;
+
+	return 0;
+}
+
+static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	/* modem control register is not present in LiteUART */
+}
+
+static unsigned int liteuart_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+}
+
+static void liteuart_stop_tx(struct uart_port *port)
+{
+}
+
+static void liteuart_start_tx(struct uart_port *port)
+{
+	struct circ_buf *xmit = &port->state->xmit;
+	unsigned char ch;
+
+	if (unlikely(port->x_char)) {
+		litex_write8(port->membase + OFF_RXTX, port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+	} else if (!uart_circ_empty(xmit)) {
+		while (xmit->head != xmit->tail) {
+			ch = xmit->buf[xmit->tail];
+			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+			port->icount.tx++;
+			liteuart_putchar(port, ch);
+		}
+	}
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+}
+
+static void liteuart_stop_rx(struct uart_port *port)
+{
+	struct liteuart_port *uart = to_liteuart_port(port);
+
+	/* just delete timer */
+	del_timer(&uart->timer);
+}
+
+static void liteuart_break_ctl(struct uart_port *port, int break_state)
+{
+	/* LiteUART doesn't support sending break signal */
+}
+
+static int liteuart_startup(struct uart_port *port)
+{
+	struct liteuart_port *uart = to_liteuart_port(port);
+
+	/* disable events */
+	litex_write8(port->membase + OFF_EV_ENABLE, 0);
+
+	/* prepare timer for polling */
+	timer_setup(&uart->timer, liteuart_timer, 0);
+	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+
+	return 0;
+}
+
+static void liteuart_shutdown(struct uart_port *port)
+{
+}
+
+static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
+				 struct ktermios *old)
+{
+	unsigned int baud;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	/* update baudrate */
+	baud = uart_get_baud_rate(port, new, old, 0, 460800);
+	uart_update_timeout(port, new->c_cflag, baud);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char *liteuart_type(struct uart_port *port)
+{
+	return "liteuart";
+}
+
+static void liteuart_release_port(struct uart_port *port)
+{
+}
+
+static int liteuart_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void liteuart_config_port(struct uart_port *port, int flags)
+{
+	/*
+	 * Driver core for serial ports forces a non-zero value for port type.
+	 * Write an arbitrary value here to accommodate the serial core driver,
+	 * as ID part of UAPI is redundant.
+	 */
+	port->type = 1;
+}
+
+static int liteuart_verify_port(struct uart_port *port,
+				struct serial_struct *ser)
+{
+	if (port->type != PORT_UNKNOWN && ser->type != 1)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct uart_ops liteuart_ops = {
+	.tx_empty	= liteuart_tx_empty,
+	.set_mctrl	= liteuart_set_mctrl,
+	.get_mctrl	= liteuart_get_mctrl,
+	.stop_tx	= liteuart_stop_tx,
+	.start_tx	= liteuart_start_tx,
+	.stop_rx	= liteuart_stop_rx,
+	.break_ctl	= liteuart_break_ctl,
+	.startup	= liteuart_startup,
+	.shutdown	= liteuart_shutdown,
+	.set_termios	= liteuart_set_termios,
+	.type		= liteuart_type,
+	.release_port	= liteuart_release_port,
+	.request_port	= liteuart_request_port,
+	.config_port	= liteuart_config_port,
+	.verify_port	= liteuart_verify_port,
+};
+
+static int liteuart_probe(struct platform_device *pdev)
+{
+	struct liteuart_port *uart;
+	struct uart_port *port;
+	struct xa_limit limit;
+	int dev_id, ret;
+
+	/* look for aliases; auto-enumerate for free index if not found */
+	dev_id = of_alias_get_id(pdev->dev.of_node, "serial");
+	if (dev_id < 0)
+		limit = XA_LIMIT(0, CONFIG_SERIAL_LITEUART_MAX_PORTS);
+	else
+		limit = XA_LIMIT(dev_id, dev_id);
+
+	uart = devm_kzalloc(&pdev->dev, sizeof(struct liteuart_port), GFP_KERNEL);
+	if (!uart)
+		return -ENOMEM;
+
+	ret = xa_alloc(&liteuart_array, &dev_id, uart, limit, GFP_KERNEL);
+	if (ret)
+		return ret;
+
+	uart->id = dev_id;
+	port = &uart->port;
+
+	/* get membase */
+	port->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (!port->membase)
+		return -ENXIO;
+
+	/* values not from device tree */
+	port->dev = &pdev->dev;
+	port->iotype = UPIO_MEM;
+	port->flags = UPF_BOOT_AUTOCONF;
+	port->ops = &liteuart_ops;
+	port->regshift = 2;
+	port->fifosize = 16;
+	port->iobase = 1;
+	port->type = PORT_UNKNOWN;
+	port->line = dev_id;
+	spin_lock_init(&port->lock);
+
+	return uart_add_one_port(&liteuart_driver, &uart->port);
+}
+
+static int liteuart_remove(struct platform_device *pdev)
+{
+	struct uart_port *port = platform_get_drvdata(pdev);
+	struct liteuart_port *uart = to_liteuart_port(port);
+
+	xa_erase(&liteuart_array, uart->id);
+
+	return 0;
+}
+
+static const struct of_device_id liteuart_of_match[] = {
+	{ .compatible = "litex,liteuart" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, liteuart_of_match);
+
+static struct platform_driver liteuart_platform_driver = {
+	.probe = liteuart_probe,
+	.remove = liteuart_remove,
+	.driver = {
+		.name = "liteuart",
+		.of_match_table = liteuart_of_match,
+	},
+};
+
+#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
+
+static void liteuart_console_write(struct console *co, const char *s,
+	unsigned int count)
+{
+	struct liteuart_port *uart;
+	struct uart_port *port;
+	unsigned long flags;
+
+	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
+	port = &uart->port;
+
+	spin_lock_irqsave(&port->lock, flags);
+	uart_console_write(port, s, count, liteuart_putchar);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static int liteuart_console_setup(struct console *co, char *options)
+{
+	struct liteuart_port *uart;
+	struct uart_port *port;
+	int baud = 115200;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	uart = (struct liteuart_port *)xa_load(&liteuart_array, co->index);
+	if (!uart)
+		return -ENODEV;
+
+	port = &uart->port;
+	if (!port->membase)
+		return -ENODEV;
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(port, co, baud, parity, bits, flow);
+}
+
+static struct console liteuart_console = {
+	.name = "liteuart",
+	.write = liteuart_console_write,
+	.device = uart_console_device,
+	.setup = liteuart_console_setup,
+	.flags = CON_PRINTBUFFER,
+	.index = -1,
+	.data = &liteuart_driver,
+};
+
+static int __init liteuart_console_init(void)
+{
+	register_console(&liteuart_console);
+
+	return 0;
+}
+console_initcall(liteuart_console_init);
+#endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
+
+static int __init liteuart_init(void)
+{
+	int res;
+
+	res = uart_register_driver(&liteuart_driver);
+	if (res)
+		return res;
+
+	res = platform_driver_register(&liteuart_platform_driver);
+	if (res) {
+		uart_unregister_driver(&liteuart_driver);
+		return res;
+	}
+
+	return 0;
+}
+
+static void __exit liteuart_exit(void)
+{
+	platform_driver_unregister(&liteuart_platform_driver);
+	uart_unregister_driver(&liteuart_driver);
+}
+
+module_init(liteuart_init);
+module_exit(liteuart_exit);
+
+MODULE_AUTHOR("Antmicro <www.antmicro.com>");
+MODULE_DESCRIPTION("LiteUART serial driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform: liteuart");

include/linux/litex.h

@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common LiteX header providing
+ * helper functions for accessing CSRs.
+ *
+ * Implementation of the functions is provided by
+ * the LiteX SoC Controller driver.
+ *
+ * Copyright (C) 2019-2020 Antmicro <www.antmicro.com>
+ */
+
+#ifndef _LINUX_LITEX_H
+#define _LINUX_LITEX_H
+
+#include <linux/io.h>
+#include <linux/types.h>
+#include <linux/compiler_types.h>
+
+/*
+ * The parameters below are true for LiteX SoCs configured for 8-bit CSR Bus,
+ * 32-bit aligned.
+ *
+ * Supporting other configurations will require extending the logic in this
+ * header and in the LiteX SoC controller driver.
+ */
+#define LITEX_REG_SIZE	  0x4
+#define LITEX_SUBREG_SIZE	0x1
+#define LITEX_SUBREG_SIZE_BIT	 (LITEX_SUBREG_SIZE * 8)
+
+#define WRITE_LITEX_SUBREGISTER(val, base_offset, subreg_id) \
+	writel((u32 __force)cpu_to_le32(val), base_offset + (LITEX_REG_SIZE * subreg_id))
+
+#define READ_LITEX_SUBREGISTER(base_offset, subreg_id) \
+	le32_to_cpu((__le32 __force)readl(base_offset + (LITEX_REG_SIZE * subreg_id)))
+
+void litex_set_reg(void __iomem *reg, unsigned long reg_sz, unsigned long val);
+
+unsigned long litex_get_reg(void __iomem *reg, unsigned long reg_sz);
+
+static inline void litex_write8(void __iomem *reg, u8 val)
+{
+	WRITE_LITEX_SUBREGISTER(val, reg, 0);
+}
+
+static inline void litex_write16(void __iomem *reg, u16 val)
+{
+	WRITE_LITEX_SUBREGISTER(val >> 8, reg, 0);
+	WRITE_LITEX_SUBREGISTER(val, reg, 1);
+}
+
+static inline void litex_write32(void __iomem *reg, u32 val)
+{
+	WRITE_LITEX_SUBREGISTER(val >> 24, reg, 0);
+	WRITE_LITEX_SUBREGISTER(val >> 16, reg, 1);
+	WRITE_LITEX_SUBREGISTER(val >> 8, reg, 2);
+	WRITE_LITEX_SUBREGISTER(val, reg, 3);
+}
+
+static inline void litex_write64(void __iomem *reg, u64 val)
+{
+	WRITE_LITEX_SUBREGISTER(val >> 56, reg, 0);
+	WRITE_LITEX_SUBREGISTER(val >> 48, reg, 1);
+	WRITE_LITEX_SUBREGISTER(val >> 40, reg, 2);
+	WRITE_LITEX_SUBREGISTER(val >> 32, reg, 3);
+	WRITE_LITEX_SUBREGISTER(val >> 24, reg, 4);
+	WRITE_LITEX_SUBREGISTER(val >> 16, reg, 5);
+	WRITE_LITEX_SUBREGISTER(val >> 8, reg, 6);
+	WRITE_LITEX_SUBREGISTER(val, reg, 7);
+}
+
+static inline u8 litex_read8(void __iomem *reg)
+{
+	return READ_LITEX_SUBREGISTER(reg, 0);
+}
+
+static inline u16 litex_read16(void __iomem *reg)
+{
+	return (READ_LITEX_SUBREGISTER(reg, 0) << 8)
+		| (READ_LITEX_SUBREGISTER(reg, 1));
+}
+
+static inline u32 litex_read32(void __iomem *reg)
+{
+	return (READ_LITEX_SUBREGISTER(reg, 0) << 24)
+		| (READ_LITEX_SUBREGISTER(reg, 1) << 16)
+		| (READ_LITEX_SUBREGISTER(reg, 2) << 8)
+		| (READ_LITEX_SUBREGISTER(reg, 3));
+}
+
+static inline u64 litex_read64(void __iomem *reg)
+{
+	return ((u64)READ_LITEX_SUBREGISTER(reg, 0) << 56)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 1) << 48)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 2) << 40)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 3) << 32)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 4) << 24)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 5) << 16)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 6) << 8)
+		| ((u64)READ_LITEX_SUBREGISTER(reg, 7));
+}
+
+#endif /* _LINUX_LITEX_H */