[PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Paul Walmsley]

This series adds a serial driver, with console support, for the
UART IP block present on the SiFive FU540 SoC.  The programming
model is straightforward, but unique.

Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
open-source FSBL (with appropriate patches to the DT data).

This fifth version fixes a bug in the set_termios handler,
found by Andreas Schwab <schwab@suse.de>.

The patches in this series can also be found, with the PRCI patches,
DT patches, and DT prerequisite patch, at:

https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4


- Paul

Paul Walmsley (2):
  dt-bindings: serial: add documentation for the SiFive UART driver
  tty: serial: add driver for the SiFive UART

 .../bindings/serial/sifive-serial.txt         |   33 +
 drivers/tty/serial/Kconfig                    |   24 +
 drivers/tty/serial/Makefile                   |    1 +
 drivers/tty/serial/sifive.c                   | 1056 +++++++++++++++++
 include/uapi/linux/serial_core.h              |    3 +
 5 files changed, 1117 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/sifive-serial.txt
 create mode 100644 drivers/tty/serial/sifive.c

-- 
2.20.1


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[PATCH v5 1/2] dt-bindings: serial: add documentation for the SiFive UART driver

[Paul Walmsley]

Add DT binding documentation for the Linux driver for the SiFive
asynchronous serial IP block.

This revision incorporates changes based on feedback from Rob
Herring <robh@kernel.org>.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: linux-serial@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
---
 .../bindings/serial/sifive-serial.txt         | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/sifive-serial.txt

diff --git a/Documentation/devicetree/bindings/serial/sifive-serial.txt b/Documentation/devicetree/bindings/serial/sifive-serial.txt
new file mode 100644
index 000000000000..c86b1e524159
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/sifive-serial.txt
@@ -0,0 +1,33 @@
+SiFive asynchronous serial interface (UART)
+
+Required properties:
+
+- compatible: should be something similar to
+	      "sifive,<chip>-uart" for the UART as integrated
+	      on a particular chip, and "sifive,uart<version>" for the
+	      general UART IP block programming model.	Supported
+	      compatible strings as of the date of this writing are:
+	      "sifive,fu540-c000-uart" for the SiFive UART v0 as
+	      integrated onto the SiFive FU540 chip, or "sifive,uart0"
+	      for the SiFive UART v0 IP block with no chip integration
+	      tweaks (if any)
+- reg: address and length of the register space
+- interrupts: Should contain the UART interrupt identifier
+- clocks: Should contain a clock identifier for the UART's parent clock
+
+
+UART HDL that corresponds to the IP block version numbers can be found
+here:
+
+https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/uart
+
+
+Example:
+
+uart0: serial@10010000 {
+	compatible = "sifive,fu540-c000-uart", "sifive,uart0";
+	interrupt-parent = <&plic0>;
+	interrupts = <80>;
+	reg = <0x0 0x10010000 0x0 0x1000>;
+	clocks = <&prci PRCI_CLK_TLCLK>;
+};
-- 
2.20.1


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Re: [PATCH v5 1/2] dt-bindings: serial: add documentation for the SiFive UART driver

[Rob Herring]

On Fri, Apr 12, 2019 at 9:01 PM Paul Walmsley <paul.walmsley@sifive.com> wrote:
>
> Add DT binding documentation for the Linux driver for the SiFive
> asynchronous serial IP block.
>
> This revision incorporates changes based on feedback from Rob
> Herring <robh@kernel.org>.
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> Signed-off-by: Paul Walmsley <paul@pwsan.com>
> Cc: linux-serial@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Cc: linux-riscv@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> ---
>  .../bindings/serial/sifive-serial.txt         | 33 +++++++++++++++++++
>  1 file changed, 33 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/sifive-serial.txt

Reviewed-by: Rob Herring <robh@kernel.org>

However, what about flow-control configuration? You'd better think now
about what the default is and overriding that.

Rob

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Re: [PATCH v5 1/2] dt-bindings: serial: add documentation for the SiFive UART driver

[Paul Walmsley]

On Fri, 26 Apr 2019, Rob Herring wrote:

> On Fri, Apr 12, 2019 at 9:01 PM Paul Walmsley <paul.walmsley@sifive.com> wrote:
> >
> > Add DT binding documentation for the Linux driver for the SiFive
> > asynchronous serial IP block.
> >
> > This revision incorporates changes based on feedback from Rob
> > Herring <robh@kernel.org>.
> >
> > Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> > Signed-off-by: Paul Walmsley <paul@pwsan.com>
> > Cc: linux-serial@vger.kernel.org
> > Cc: devicetree@vger.kernel.org
> > Cc: linux-riscv@lists.infradead.org
> > Cc: linux-kernel@vger.kernel.org
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Palmer Dabbelt <palmer@sifive.com>
> > ---
> >  .../bindings/serial/sifive-serial.txt         | 33 +++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/serial/sifive-serial.txt
> 
> Reviewed-by: Rob Herring <robh@kernel.org>

Thanks Rob.

> However, what about flow-control configuration? You'd better think now
> about what the default is and overriding that.

The underlying IP doesn't support it.

https://github.com/sifive/riscv-linux/blob/dev/paulw/dts-v5.1-rc6-experimental/drivers/tty/serial/sifive.c#L30


- Paul


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[PATCH v5 2/2] tty: serial: add driver for the SiFive UART

[Paul Walmsley]

Add a serial driver for the SiFive UART, found on SiFive FU540 devices
(among others).

The underlying serial IP block is relatively basic, and currently does
not support serial break detection.  Further information on the IP
block can be found in the documentation and Chisel sources:

    https://static.dev.sifive.com/FU540-C000-v1.0.pdf

    https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/uart

This driver was written in collaboration with Wesley Terpstra
<wesley@sifive.com>.

Tested on a SiFive HiFive Unleashed A00 board, using BBL and the open-
source FSBL (using a DT file based on what's targeted for mainline).

This revision incorporates changes based on comments by Julia Lawall
<julia.lawall@lip6.fr>, Emil Renner Berthing <kernel@esmil.dk>, and
Andreas Schwab <schwab@suse.de>.  Thanks also to Andreas for testing
the driver with his userspace and reporting a bug with the
set_termios implementation.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Wesley Terpstra <wesley@sifive.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Emil Renner Berthing <kernel@esmil.dk>
Cc: Andreas Schwab <schwab@suse.de>
---
 drivers/tty/serial/Kconfig       |   24 +
 drivers/tty/serial/Makefile      |    1 +
 drivers/tty/serial/sifive.c      | 1056 ++++++++++++++++++++++++++++++
 include/uapi/linux/serial_core.h |    3 +
 4 files changed, 1084 insertions(+)
 create mode 100644 drivers/tty/serial/sifive.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 72966bc0ac76..561e053b690a 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1095,6 +1095,30 @@ config SERIAL_OMAP_CONSOLE
 	  your boot loader about how to pass options to the kernel at
 	  boot time.)
 
+config SERIAL_SIFIVE
+	tristate "SiFive UART support"
+	depends on OF
+	select SERIAL_CORE
+	help
+	  Select this option if you are building a kernel for a device that
+	  contains a SiFive UART IP block.  This type of UART is present on
+	  SiFive FU540 SoCs, among others.
+
+config SERIAL_SIFIVE_CONSOLE
+	bool "Console on SiFive UART"
+	depends on SERIAL_SIFIVE=y
+	select SERIAL_CORE_CONSOLE
+	help
+	  Select this option if you would like to use a SiFive UART as the
+	  system console.
+
+	  Even if you say Y here, the currently visible virtual console
+	  (/dev/tty0) will still be used as the system console by default, but
+	  you can alter that using a kernel command line option such as
+	  "console=ttySIFx". (Try "man bootparam" or see the documentation of
+	  your boot loader about how to pass options to the kernel at
+	  boot time.)
+
 config SERIAL_LANTIQ
 	bool "Lantiq serial driver"
 	depends on LANTIQ
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 40b702aaa85e..2aff1d07d08b 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_SERIAL_PIC32)	+= pic32_uart.o
 obj-$(CONFIG_SERIAL_MPS2_UART)	+= mps2-uart.o
 obj-$(CONFIG_SERIAL_OWL)	+= owl-uart.o
 obj-$(CONFIG_SERIAL_RDA)	+= rda-uart.o
+obj-$(CONFIG_SERIAL_SIFIVE)	+= sifive.o
 
 # GPIOLIB helpers for modem control lines
 obj-$(CONFIG_SERIAL_MCTRL_GPIO)	+= serial_mctrl_gpio.o
diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
new file mode 100644
index 000000000000..be4687814353
--- /dev/null
+++ b/drivers/tty/serial/sifive.c
@@ -0,0 +1,1056 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * SiFive UART driver
+ * Copyright (C) 2018 Paul Walmsley <paul@pwsan.com>
+ * Copyright (C) 2018-2019 SiFive
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Based partially on:
+ * - drivers/tty/serial/pxa.c
+ * - drivers/tty/serial/amba-pl011.c
+ * - drivers/tty/serial/uartlite.c
+ * - drivers/tty/serial/omap-serial.c
+ * - drivers/pwm/pwm-sifive.c
+ *
+ * See the following sources for further documentation:
+ * - Chapter 19 "Universal Asynchronous Receiver/Transmitter (UART)" of
+ *   SiFive FE310-G000 v2p3
+ * - The tree/master/src/main/scala/devices/uart directory of
+ *   https://github.com/sifive/sifive-blocks/
+ *
+ * The SiFive UART design is not 8250-compatible.  The following common
+ * features are not supported:
+ * - Word lengths other than 8 bits
+ * - Break handling
+ * - Parity
+ * - Flow control
+ * - Modem signals (DSR, RI, etc.)
+ * On the other hand, the design is free from the baggage of the 8250
+ * programming model.
+ */
+
+#include <linux/clk.h>
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+/*
+ * Register offsets
+ */
+
+/* TXDATA */
+#define SIFIVE_SERIAL_TXDATA_OFFS		0x0
+#define SIFIVE_SERIAL_TXDATA_FULL_SHIFT		31
+#define SIFIVE_SERIAL_TXDATA_FULL_MASK		(1 << SIFIVE_SERIAL_TXDATA_FULL_SHIFT)
+#define SIFIVE_SERIAL_TXDATA_DATA_SHIFT		0
+#define SIFIVE_SERIAL_TXDATA_DATA_MASK		(0xff << SIFIVE_SERIAL_TXDATA_DATA_SHIFT)
+
+/* RXDATA */
+#define SIFIVE_SERIAL_RXDATA_OFFS		0x4
+#define SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT	31
+#define SIFIVE_SERIAL_RXDATA_EMPTY_MASK		(1 << SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT)
+#define SIFIVE_SERIAL_RXDATA_DATA_SHIFT		0
+#define SIFIVE_SERIAL_RXDATA_DATA_MASK		(0xff << SIFIVE_SERIAL_RXDATA_DATA_SHIFT)
+
+/* TXCTRL */
+#define SIFIVE_SERIAL_TXCTRL_OFFS		0x8
+#define SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT	16
+#define SIFIVE_SERIAL_TXCTRL_TXCNT_MASK		(0x7 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT)
+#define SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT	1
+#define SIFIVE_SERIAL_TXCTRL_NSTOP_MASK		(1 << SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT)
+#define SIFIVE_SERIAL_TXCTRL_TXEN_SHIFT		0
+#define SIFIVE_SERIAL_TXCTRL_TXEN_MASK		(1 << SIFIVE_SERIAL_TXCTRL_TXEN_SHIFT)
+
+/* RXCTRL */
+#define SIFIVE_SERIAL_RXCTRL_OFFS		0xC
+#define SIFIVE_SERIAL_RXCTRL_RXCNT_SHIFT	16
+#define SIFIVE_SERIAL_RXCTRL_RXCNT_MASK		(0x7 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT)
+#define SIFIVE_SERIAL_RXCTRL_RXEN_SHIFT		0
+#define SIFIVE_SERIAL_RXCTRL_RXEN_MASK		(1 << SIFIVE_SERIAL_RXCTRL_RXEN_SHIFT)
+
+/* IE */
+#define SIFIVE_SERIAL_IE_OFFS			0x10
+#define SIFIVE_SERIAL_IE_RXWM_SHIFT		1
+#define SIFIVE_SERIAL_IE_RXWM_MASK		(1 << SIFIVE_SERIAL_IE_RXWM_SHIFT)
+#define SIFIVE_SERIAL_IE_TXWM_SHIFT		0
+#define SIFIVE_SERIAL_IE_TXWM_MASK		(1 << SIFIVE_SERIAL_IE_TXWM_SHIFT)
+
+/* IP */
+#define SIFIVE_SERIAL_IP_OFFS			0x14
+#define SIFIVE_SERIAL_IP_RXWM_SHIFT		1
+#define SIFIVE_SERIAL_IP_RXWM_MASK		(1 << SIFIVE_SERIAL_IP_RXWM_SHIFT)
+#define SIFIVE_SERIAL_IP_TXWM_SHIFT		0
+#define SIFIVE_SERIAL_IP_TXWM_MASK		(1 << SIFIVE_SERIAL_IP_TXWM_SHIFT)
+
+/* DIV */
+#define SIFIVE_SERIAL_DIV_OFFS			0x18
+#define SIFIVE_SERIAL_DIV_DIV_SHIFT		0
+#define SIFIVE_SERIAL_DIV_DIV_MASK		(0xffff << SIFIVE_SERIAL_IP_DIV_SHIFT)
+
+/*
+ * Config macros
+ */
+
+/*
+ * SIFIVE_SERIAL_MAX_PORTS: maximum number of UARTs on a device that can
+ *                          host a serial console
+ */
+#define SIFIVE_SERIAL_MAX_PORTS			8
+
+/*
+ * SIFIVE_DEFAULT_BAUD_RATE: default baud rate that the driver should
+ *                           configure itself to use
+ */
+#define SIFIVE_DEFAULT_BAUD_RATE		115200
+
+/* SIFIVE_SERIAL_NAME: our driver's name that we pass to the operating system */
+#define SIFIVE_SERIAL_NAME			"sifive-serial"
+
+/* SIFIVE_TTY_PREFIX: tty name prefix for SiFive serial ports */
+#define SIFIVE_TTY_PREFIX			"ttySIF"
+
+/* SIFIVE_TX_FIFO_DEPTH: depth of the TX FIFO (in bytes) */
+#define SIFIVE_TX_FIFO_DEPTH			8
+
+/* SIFIVE_RX_FIFO_DEPTH: depth of the TX FIFO (in bytes) */
+#define SIFIVE_RX_FIFO_DEPTH			8
+
+#if (SIFIVE_TX_FIFO_DEPTH != SIFIVE_RX_FIFO_DEPTH)
+#error Driver does not support configurations with different TX, RX FIFO sizes
+#endif
+
+/*
+ *
+ */
+
+/**
+ * sifive_serial_port - driver-specific data extension to struct uart_port
+ * @port: struct uart_port embedded in this struct
+ * @dev: struct device *
+ * @ier: shadowed copy of the interrupt enable register
+ * @clkin_rate: input clock to the UART IP block.
+ * @baud_rate: UART serial line rate (e.g., 115200 baud)
+ * @clk_notifier: clock rate change notifier for upstream clock changes
+ *
+ * Configuration data specific to this SiFive UART.
+ */
+struct sifive_serial_port {
+	struct uart_port	port;
+	struct device		*dev;
+	unsigned char		ier;
+	unsigned long		clkin_rate;
+	unsigned long		baud_rate;
+	struct clk		*clk;
+	struct notifier_block	clk_notifier;
+};
+
+/*
+ * Structure container-of macros
+ */
+
+#define port_to_sifive_serial_port(p) (container_of((p), \
+						    struct sifive_serial_port, \
+						    port))
+
+#define notifier_to_sifive_serial_port(nb) (container_of((nb), \
+							 struct sifive_serial_port, \
+							 clk_notifier))
+
+/*
+ * Forward declarations
+ */
+static void sifive_serial_stop_tx(struct uart_port *port);
+
+/*
+ * Internal functions
+ */
+
+/**
+ * __ssp_early_writel() - write to a SiFive serial port register (early)
+ * @port: pointer to a struct uart_port record
+ * @offs: register address offset from the IP block base address
+ * @v: value to write to the register
+ *
+ * Given a pointer @port to a struct uart_port record, write the value
+ * @v to the IP block register address offset @offs.  This function is
+ * intended for early console use.
+ *
+ * Context: Intended to be used only by the earlyconsole code.
+ */
+static void __ssp_early_writel(u32 v, u16 offs, struct uart_port *port)
+{
+	writel_relaxed(v, port->membase + offs);
+}
+
+/**
+ * __ssp_early_readl() - read from a SiFive serial port register (early)
+ * @port: pointer to a struct uart_port record
+ * @offs: register address offset from the IP block base address
+ *
+ * Given a pointer @port to a struct uart_port record, read the
+ * contents of the IP block register located at offset @offs from the
+ * IP block base and return it.  This function is intended for early
+ * console use.
+ *
+ * Context: Intended to be called only by the earlyconsole code or by
+ *          __ssp_readl() or __ssp_writel() (in this driver)
+ *
+ * Returns: the register value read from the UART.
+ */
+static u32 __ssp_early_readl(struct uart_port *port, u16 offs)
+{
+	return readl_relaxed(port->membase + offs);
+}
+
+/**
+ * __ssp_writel() - write to a SiFive serial port register
+ * @v: value to write to the register
+ * @offs: register address offset from the IP block base address
+ * @ssp: pointer to a struct sifive_serial_port record
+ *
+ * Write the value @v to the IP block register located at offset @offs from the
+ * IP block base, given a pointer @ssp to a struct sifive_serial_port record.
+ *
+ * Context: Any context.
+ */
+static void __ssp_writel(u32 v, u16 offs, struct sifive_serial_port *ssp)
+{
+	__ssp_early_writel(v, offs, &ssp->port);
+}
+
+/**
+ * __ssp_readl() - read from a SiFive serial port register
+ * @ssp: pointer to a struct sifive_serial_port record
+ * @offs: register address offset from the IP block base address
+ *
+ * Read the contents of the IP block register located at offset @offs from the
+ * IP block base, given a pointer @ssp to a struct sifive_serial_port record.
+ *
+ * Context: Any context.
+ *
+ * Returns: the value of the UART register
+ */
+static u32 __ssp_readl(struct sifive_serial_port *ssp, u16 offs)
+{
+	return __ssp_early_readl(&ssp->port, offs);
+}
+
+/**
+ * sifive_serial_is_txfifo_full() - is the TXFIFO full?
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Read the transmit FIFO "full" bit, returning a non-zero value if the
+ * TX FIFO is full, or zero if space remains.  Intended to be used to prevent
+ * writes to the TX FIFO when it's full.
+ *
+ * Returns: SIFIVE_SERIAL_TXDATA_FULL_MASK (non-zero) if the transmit FIFO
+ * is full, or 0 if space remains.
+ */
+static int sifive_serial_is_txfifo_full(struct sifive_serial_port *ssp)
+{
+	return __ssp_readl(ssp, SIFIVE_SERIAL_TXDATA_OFFS) &
+		SIFIVE_SERIAL_TXDATA_FULL_MASK;
+}
+
+/**
+ * __ssp_transmit_char() - enqueue a byte to transmit onto the TX FIFO
+ * @ssp: pointer to a struct sifive_serial_port
+ * @ch: character to transmit
+ *
+ * Enqueue a byte @ch onto the transmit FIFO, given a pointer @ssp to the
+ * struct sifive_serial_port * to transmit on.  Caller should first check to
+ * ensure that the TXFIFO has space; see sifive_serial_is_txfifo_full().
+ *
+ * Context: Any context.
+ */
+static void __ssp_transmit_char(struct sifive_serial_port *ssp, int ch)
+{
+	__ssp_writel(ch, SIFIVE_SERIAL_TXDATA_OFFS, ssp);
+}
+
+/**
+ * __ssp_transmit_chars() - enqueue multiple bytes onto the TX FIFO
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Transfer up to a TX FIFO size's worth of characters from the Linux serial
+ * transmit buffer to the SiFive UART TX FIFO.
+ *
+ * Context: Any context.  Expects @ssp->port.lock to be held by caller.
+ */
+static void __ssp_transmit_chars(struct sifive_serial_port *ssp)
+{
+	struct circ_buf *xmit = &ssp->port.state->xmit;
+	int count;
+
+	if (ssp->port.x_char) {
+		__ssp_transmit_char(ssp, ssp->port.x_char);
+		ssp->port.icount.tx++;
+		ssp->port.x_char = 0;
+		return;
+	}
+	if (uart_circ_empty(xmit) || uart_tx_stopped(&ssp->port)) {
+		sifive_serial_stop_tx(&ssp->port);
+		return;
+	}
+	count = SIFIVE_TX_FIFO_DEPTH;
+	do {
+		__ssp_transmit_char(ssp, xmit->buf[xmit->tail]);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		ssp->port.icount.tx++;
+		if (uart_circ_empty(xmit))
+			break;
+	} while (--count > 0);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&ssp->port);
+
+	if (uart_circ_empty(xmit))
+		sifive_serial_stop_tx(&ssp->port);
+}
+
+/**
+ * __ssp_enable_txwm() - enable transmit watermark interrupts
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Enable interrupt generation when the transmit FIFO watermark is reached
+ * on the SiFive UART referred to by @ssp.
+ */
+static void __ssp_enable_txwm(struct sifive_serial_port *ssp)
+{
+	if (ssp->ier & SIFIVE_SERIAL_IE_TXWM_MASK)
+		return;
+
+	ssp->ier |= SIFIVE_SERIAL_IE_TXWM_MASK;
+	__ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
+}
+
+/**
+ * __ssp_enable_rxwm() - enable receive watermark interrupts
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Enable interrupt generation when the receive FIFO watermark is reached
+ * on the SiFive UART referred to by @ssp.
+ */
+static void __ssp_enable_rxwm(struct sifive_serial_port *ssp)
+{
+	if (ssp->ier & SIFIVE_SERIAL_IE_RXWM_MASK)
+		return;
+
+	ssp->ier |= SIFIVE_SERIAL_IE_RXWM_MASK;
+	__ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
+}
+
+/**
+ * __ssp_disable_txwm() - disable transmit watermark interrupts
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Disable interrupt generation when the transmit FIFO watermark is reached
+ * on the UART referred to by @ssp.
+ */
+static void __ssp_disable_txwm(struct sifive_serial_port *ssp)
+{
+	if (!(ssp->ier & SIFIVE_SERIAL_IE_TXWM_MASK))
+		return;
+
+	ssp->ier &= ~SIFIVE_SERIAL_IE_TXWM_MASK;
+	__ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
+}
+
+/**
+ * __ssp_disable_rxwm() - disable receive watermark interrupts
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Disable interrupt generation when the receive FIFO watermark is reached
+ * on the UART referred to by @ssp.
+ */
+static void __ssp_disable_rxwm(struct sifive_serial_port *ssp)
+{
+	if (!(ssp->ier & SIFIVE_SERIAL_IE_RXWM_MASK))
+		return;
+
+	ssp->ier &= ~SIFIVE_SERIAL_IE_RXWM_MASK;
+	__ssp_writel(ssp->ier, SIFIVE_SERIAL_IE_OFFS, ssp);
+}
+
+/**
+ * __ssp_receive_char() - receive a byte from the UART
+ * @ssp: pointer to a struct sifive_serial_port
+ * @is_empty: char pointer to return whether the RX FIFO is empty
+ *
+ * Try to read a byte from the SiFive UART RX FIFO, referenced by
+ * @ssp, and to return it.  Also returns the RX FIFO empty bit in
+ * the char pointed to by @ch.  The caller must pass the byte back to the
+ * Linux serial layer if needed.
+ *
+ * Returns: the byte read from the UART RX FIFO.
+ */
+static char __ssp_receive_char(struct sifive_serial_port *ssp, char *is_empty)
+{
+	u32 v;
+	u8 ch;
+
+	v = __ssp_readl(ssp, SIFIVE_SERIAL_RXDATA_OFFS);
+
+	if (!is_empty)
+		WARN_ON(1);
+	else
+		*is_empty = (v & SIFIVE_SERIAL_RXDATA_EMPTY_MASK) >>
+			SIFIVE_SERIAL_RXDATA_EMPTY_SHIFT;
+
+	ch = (v & SIFIVE_SERIAL_RXDATA_DATA_MASK) >>
+		SIFIVE_SERIAL_RXDATA_DATA_SHIFT;
+
+	return ch;
+}
+
+/**
+ * __ssp_receive_chars() - receive multiple bytes from the UART
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Receive up to an RX FIFO's worth of bytes from the SiFive UART referred
+ * to by @ssp and pass them up to the Linux serial layer.
+ *
+ * Context: Expects ssp->port.lock to be held by caller.
+ */
+static void __ssp_receive_chars(struct sifive_serial_port *ssp)
+{
+	unsigned char ch;
+	char is_empty;
+	int c;
+
+	for (c = SIFIVE_RX_FIFO_DEPTH; c > 0; --c) {
+		ch = __ssp_receive_char(ssp, &is_empty);
+		if (is_empty)
+			break;
+
+		ssp->port.icount.rx++;
+		uart_insert_char(&ssp->port, 0, 0, ch, TTY_NORMAL);
+	}
+
+	spin_unlock(&ssp->port.lock);
+	tty_flip_buffer_push(&ssp->port.state->port);
+	spin_lock(&ssp->port.lock);
+}
+
+/**
+ * __ssp_update_div() - calculate the divisor setting by the line rate
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Calculate the appropriate value of the clock divisor for the UART
+ * and target line rate referred to by @ssp and write it into the
+ * hardware.
+ */
+static void __ssp_update_div(struct sifive_serial_port *ssp)
+{
+	u16 div;
+
+	div = DIV_ROUND_UP(ssp->clkin_rate, ssp->baud_rate) - 1;
+
+	__ssp_writel(div, SIFIVE_SERIAL_DIV_OFFS, ssp);
+}
+
+/**
+ * __ssp_update_baud_rate() - set the UART "baud rate"
+ * @ssp: pointer to a struct sifive_serial_port
+ * @rate: new target bit rate
+ *
+ * Calculate the UART divisor value for the target bit rate @rate for the
+ * SiFive UART described by @ssp and program it into the UART.  There may
+ * be some error between the target bit rate and the actual bit rate implemented
+ * by the UART due to clock ratio granularity.
+ */
+static void __ssp_update_baud_rate(struct sifive_serial_port *ssp,
+				   unsigned int rate)
+{
+	if (ssp->baud_rate == rate)
+		return;
+
+	ssp->baud_rate = rate;
+	__ssp_update_div(ssp);
+}
+
+/**
+ * __ssp_set_stop_bits() - set the number of stop bits
+ * @ssp: pointer to a struct sifive_serial_port
+ * @nstop: 1 or 2 (stop bits)
+ *
+ * Program the SiFive UART referred to by @ssp to use @nstop stop bits.
+ */
+static void __ssp_set_stop_bits(struct sifive_serial_port *ssp, char nstop)
+{
+	u32 v;
+
+	if (nstop < 1 || nstop > 2) {
+		WARN_ON(1);
+		return;
+	}
+
+	v = __ssp_readl(ssp, SIFIVE_SERIAL_TXCTRL_OFFS);
+	v &= ~SIFIVE_SERIAL_TXCTRL_NSTOP_MASK;
+	v |= (nstop - 1) << SIFIVE_SERIAL_TXCTRL_NSTOP_SHIFT;
+	__ssp_writel(v, SIFIVE_SERIAL_TXCTRL_OFFS, ssp);
+}
+
+/**
+ * __ssp_wait_for_xmitr() - wait for an empty slot on the TX FIFO
+ * @ssp: pointer to a struct sifive_serial_port
+ *
+ * Delay while the UART TX FIFO referred to by @ssp is marked as full.
+ *
+ * Context: Any context.
+ */
+static void __maybe_unused __ssp_wait_for_xmitr(struct sifive_serial_port *ssp)
+{
+	while (sifive_serial_is_txfifo_full(ssp))
+		udelay(1); /* XXX Could probably be more intelligent here */
+}
+
+/*
+ * Linux serial API functions
+ */
+
+static void sifive_serial_stop_tx(struct uart_port *port)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_disable_txwm(ssp);
+}
+
+static void sifive_serial_stop_rx(struct uart_port *port)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_disable_rxwm(ssp);
+}
+
+static void sifive_serial_start_tx(struct uart_port *port)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_enable_txwm(ssp);
+}
+
+static irqreturn_t sifive_serial_irq(int irq, void *dev_id)
+{
+	struct sifive_serial_port *ssp = dev_id;
+	u32 ip;
+
+	spin_lock(&ssp->port.lock);
+
+	ip = __ssp_readl(ssp, SIFIVE_SERIAL_IP_OFFS);
+	if (!ip) {
+		spin_unlock(&ssp->port.lock);
+		return IRQ_NONE;
+	}
+
+	if (ip & SIFIVE_SERIAL_IP_RXWM_MASK)
+		__ssp_receive_chars(ssp);
+	if (ip & SIFIVE_SERIAL_IP_TXWM_MASK)
+		__ssp_transmit_chars(ssp);
+
+	spin_unlock(&ssp->port.lock);
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int sifive_serial_tx_empty(struct uart_port *port)
+{
+	return TIOCSER_TEMT;
+}
+
+static unsigned int sifive_serial_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR;
+}
+
+static void sifive_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	/* IP block does not support these signals */
+}
+
+static void sifive_serial_break_ctl(struct uart_port *port, int break_state)
+{
+	/* IP block does not support sending a break */
+}
+
+static int sifive_serial_startup(struct uart_port *port)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_enable_rxwm(ssp);
+
+	return 0;
+}
+
+static void sifive_serial_shutdown(struct uart_port *port)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_disable_rxwm(ssp);
+	__ssp_disable_txwm(ssp);
+}
+
+/**
+ * sifive_serial_clk_notifier() - clock post-rate-change notifier
+ * @nb: pointer to the struct notifier_block, from the notifier code
+ * @event: event mask from the notifier code
+ * @data: pointer to the struct clk_notifier_data from the notifier code
+ *
+ * On the V0 SoC, the UART IP block is derived from the CPU clock source
+ * after a synchronous divide-by-two divider, so any CPU clock rate change
+ * requires the UART baud rate to be updated.  This presumably could corrupt any
+ * serial word currently being transmitted or received.  It would probably
+ * be better to stop receives and transmits, then complete the baud rate
+ * change, then re-enable them.
+ */
+static int sifive_serial_clk_notifier(struct notifier_block *nb,
+				      unsigned long event, void *data)
+{
+	struct clk_notifier_data *cnd = data;
+	struct sifive_serial_port *ssp = notifier_to_sifive_serial_port(nb);
+
+	if (event == POST_RATE_CHANGE && ssp->clkin_rate != cnd->new_rate) {
+		ssp->clkin_rate = cnd->new_rate;
+		__ssp_update_div(ssp);
+	}
+
+	return NOTIFY_OK;
+}
+
+static void sifive_serial_set_termios(struct uart_port *port,
+				      struct ktermios *termios,
+				      struct ktermios *old)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+	unsigned long flags;
+	u32 v, old_v;
+	int rate;
+	char nstop;
+
+	if ((termios->c_cflag & CSIZE) != CS8)
+		dev_err_once(ssp->port.dev, "only 8-bit words supported\n");
+	if (termios->c_iflag & (INPCK | PARMRK))
+		dev_err_once(ssp->port.dev, "parity checking not supported\n");
+	if (termios->c_iflag & BRKINT)
+		dev_err_once(ssp->port.dev, "BREAK detection not supported\n");
+
+	/* Set number of stop bits */
+	nstop = (termios->c_cflag & CSTOPB) ? 2 : 1;
+	__ssp_set_stop_bits(ssp, nstop);
+
+	/* Set line rate */
+	rate = uart_get_baud_rate(port, termios, old, 0, ssp->clkin_rate / 16);
+	__ssp_update_baud_rate(ssp, rate);
+
+	spin_lock_irqsave(&ssp->port.lock, flags);
+
+	/* Update the per-port timeout */
+	uart_update_timeout(port, termios->c_cflag, rate);
+
+	ssp->port.read_status_mask = 0;
+
+	/* Ignore all characters if CREAD is not set */
+	v = __ssp_readl(ssp, SIFIVE_SERIAL_RXCTRL_OFFS);
+	old_v = v;
+	if ((termios->c_cflag & CREAD) == 0)
+		v &= SIFIVE_SERIAL_RXCTRL_RXEN_MASK;
+	else
+		v |= SIFIVE_SERIAL_RXCTRL_RXEN_MASK;
+	if (v != old_v)
+		__ssp_writel(v, SIFIVE_SERIAL_RXCTRL_OFFS, ssp);
+
+	spin_unlock_irqrestore(&ssp->port.lock, flags);
+}
+
+static void sifive_serial_release_port(struct uart_port *port)
+{
+}
+
+static int sifive_serial_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void sifive_serial_config_port(struct uart_port *port, int flags)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	ssp->port.type = PORT_SIFIVE_V0;
+}
+
+static int sifive_serial_verify_port(struct uart_port *port,
+				     struct serial_struct *ser)
+{
+	return -EINVAL;
+}
+
+static const char *sifive_serial_type(struct uart_port *port)
+{
+	return port->type == PORT_SIFIVE_V0 ? "SiFive UART v0" : NULL;
+}
+
+/*
+ * Early console support
+ */
+
+#ifdef CONFIG_SERIAL_EARLYCON
+static void early_sifive_serial_putc(struct uart_port *port, int c)
+{
+	while (__ssp_early_readl(port, SIFIVE_SERIAL_TXDATA_OFFS) &
+	       SIFIVE_SERIAL_TXDATA_FULL_MASK)
+		cpu_relax();
+
+	__ssp_early_writel(c, SIFIVE_SERIAL_TXDATA_OFFS, port);
+}
+
+static void early_sifive_serial_write(struct console *con, const char *s,
+				      unsigned int n)
+{
+	struct earlycon_device *dev = con->data;
+	struct uart_port *port = &dev->port;
+
+	uart_console_write(port, s, n, early_sifive_serial_putc);
+}
+
+static int __init early_sifive_serial_setup(struct earlycon_device *dev,
+					    const char *options)
+{
+	struct uart_port *port = &dev->port;
+
+	if (!port->membase)
+		return -ENODEV;
+
+	dev->con->write = early_sifive_serial_write;
+
+	return 0;
+}
+
+OF_EARLYCON_DECLARE(sifive, "sifive,uart0", early_sifive_serial_setup);
+OF_EARLYCON_DECLARE(sifive, "sifive,fu540-c000-uart0",
+		    early_sifive_serial_setup);
+#endif /* CONFIG_SERIAL_EARLYCON */
+
+/*
+ * Linux console interface
+ */
+
+#ifdef CONFIG_SERIAL_SIFIVE_CONSOLE
+
+static struct sifive_serial_port *sifive_serial_console_ports[SIFIVE_SERIAL_MAX_PORTS];
+
+static void sifive_serial_console_putchar(struct uart_port *port, int ch)
+{
+	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+
+	__ssp_wait_for_xmitr(ssp);
+	__ssp_transmit_char(ssp, ch);
+}
+
+static void sifive_serial_console_write(struct console *co, const char *s,
+					unsigned int count)
+{
+	struct sifive_serial_port *ssp = sifive_serial_console_ports[co->index];
+	unsigned long flags;
+	unsigned int ier;
+	int locked = 1;
+
+	if (!ssp)
+		return;
+
+	local_irq_save(flags);
+	if (ssp->port.sysrq)
+		locked = 0;
+	else if (oops_in_progress)
+		locked = spin_trylock(&ssp->port.lock);
+	else
+		spin_lock(&ssp->port.lock);
+
+	ier = __ssp_readl(ssp, SIFIVE_SERIAL_IE_OFFS);
+	__ssp_writel(0, SIFIVE_SERIAL_IE_OFFS, ssp);
+
+	uart_console_write(&ssp->port, s, count, sifive_serial_console_putchar);
+
+	__ssp_writel(ier, SIFIVE_SERIAL_IE_OFFS, ssp);
+
+	if (locked)
+		spin_unlock(&ssp->port.lock);
+	local_irq_restore(flags);
+}
+
+static int __init sifive_serial_console_setup(struct console *co, char *options)
+{
+	struct sifive_serial_port *ssp;
+	int baud = SIFIVE_DEFAULT_BAUD_RATE;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (co->index < 0 || co->index >= SIFIVE_SERIAL_MAX_PORTS)
+		return -ENODEV;
+
+	ssp = sifive_serial_console_ports[co->index];
+	if (!ssp)
+		return -ENODEV;
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(&ssp->port, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver sifive_serial_uart_driver;
+
+static struct console sifive_serial_console = {
+	.name		= SIFIVE_TTY_PREFIX,
+	.write		= sifive_serial_console_write,
+	.device		= uart_console_device,
+	.setup		= sifive_serial_console_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+	.data		= &sifive_serial_uart_driver,
+};
+
+static int __init sifive_console_init(void)
+{
+	register_console(&sifive_serial_console);
+	return 0;
+}
+
+console_initcall(sifive_console_init);
+
+static void __ssp_add_console_port(struct sifive_serial_port *ssp)
+{
+	sifive_serial_console_ports[ssp->port.line] = ssp;
+}
+
+static void __ssp_remove_console_port(struct sifive_serial_port *ssp)
+{
+	sifive_serial_console_ports[ssp->port.line] = 0;
+}
+
+#define SIFIVE_SERIAL_CONSOLE	(&sifive_serial_console)
+
+#else
+
+#define SIFIVE_SERIAL_CONSOLE	NULL
+
+static void __ssp_add_console_port(struct sifive_serial_port *ssp)
+{}
+static void __ssp_remove_console_port(struct sifive_serial_port *ssp)
+{}
+
+#endif
+
+static const struct uart_ops sifive_serial_uops = {
+	.tx_empty	= sifive_serial_tx_empty,
+	.set_mctrl	= sifive_serial_set_mctrl,
+	.get_mctrl	= sifive_serial_get_mctrl,
+	.stop_tx	= sifive_serial_stop_tx,
+	.start_tx	= sifive_serial_start_tx,
+	.stop_rx	= sifive_serial_stop_rx,
+	.break_ctl	= sifive_serial_break_ctl,
+	.startup	= sifive_serial_startup,
+	.shutdown	= sifive_serial_shutdown,
+	.set_termios	= sifive_serial_set_termios,
+	.type		= sifive_serial_type,
+	.release_port	= sifive_serial_release_port,
+	.request_port	= sifive_serial_request_port,
+	.config_port	= sifive_serial_config_port,
+	.verify_port	= sifive_serial_verify_port,
+};
+
+static struct uart_driver sifive_serial_uart_driver = {
+	.owner		= THIS_MODULE,
+	.driver_name	= SIFIVE_SERIAL_NAME,
+	.dev_name	= SIFIVE_TTY_PREFIX,
+	.nr		= SIFIVE_SERIAL_MAX_PORTS,
+	.cons		= SIFIVE_SERIAL_CONSOLE,
+};
+
+static int sifive_serial_probe(struct platform_device *pdev)
+{
+	struct sifive_serial_port *ssp;
+	struct resource *mem;
+	struct clk *clk;
+	void __iomem *base;
+	int irq, id, r;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "could not acquire interrupt\n");
+		return -EPROBE_DEFER;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, mem);
+	if (IS_ERR(base)) {
+		dev_err(&pdev->dev, "could not acquire device memory\n");
+		return PTR_ERR(base);
+	}
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "unable to find controller clock\n");
+		return PTR_ERR(clk);
+	}
+
+	id = of_alias_get_id(pdev->dev.of_node, "serial");
+	if (id < 0) {
+		dev_err(&pdev->dev, "missing aliases entry\n");
+		return id;
+	}
+
+#ifdef CONFIG_SERIAL_SIFIVE_CONSOLE
+	if (id > SIFIVE_SERIAL_MAX_PORTS) {
+		dev_err(&pdev->dev, "too many UARTs (%d)\n", id);
+		return -EINVAL;
+	}
+#endif
+
+	ssp = devm_kzalloc(&pdev->dev, sizeof(*ssp), GFP_KERNEL);
+	if (!ssp)
+		return -ENOMEM;
+
+	ssp->port.dev = &pdev->dev;
+	ssp->port.type = PORT_SIFIVE_V0;
+	ssp->port.iotype = UPIO_MEM;
+	ssp->port.irq = irq;
+	ssp->port.fifosize = SIFIVE_TX_FIFO_DEPTH;
+	ssp->port.ops = &sifive_serial_uops;
+	ssp->port.line = id;
+	ssp->port.mapbase = mem->start;
+	ssp->port.membase = base;
+	ssp->dev = &pdev->dev;
+	ssp->clk = clk;
+	ssp->clk_notifier.notifier_call = sifive_serial_clk_notifier;
+
+	r = clk_notifier_register(ssp->clk, &ssp->clk_notifier);
+	if (r) {
+		dev_err(&pdev->dev, "could not register clock notifier: %d\n",
+			r);
+		goto probe_out1;
+	}
+
+	/* Set up clock divider */
+	ssp->clkin_rate = clk_get_rate(ssp->clk);
+	ssp->baud_rate = SIFIVE_DEFAULT_BAUD_RATE;
+	__ssp_update_div(ssp);
+
+	platform_set_drvdata(pdev, ssp);
+
+	/* Enable transmits and set the watermark level to 1 */
+	__ssp_writel((1 << SIFIVE_SERIAL_TXCTRL_TXCNT_SHIFT) |
+		     SIFIVE_SERIAL_TXCTRL_TXEN_MASK,
+		     SIFIVE_SERIAL_TXCTRL_OFFS, ssp);
+
+	/* Enable receives and set the watermark level to 0 */
+	__ssp_writel((0 << SIFIVE_SERIAL_RXCTRL_RXCNT_SHIFT) |
+		     SIFIVE_SERIAL_RXCTRL_RXEN_MASK,
+		     SIFIVE_SERIAL_RXCTRL_OFFS, ssp);
+
+	r = request_irq(ssp->port.irq, sifive_serial_irq, ssp->port.irqflags,
+			dev_name(&pdev->dev), ssp);
+	if (r) {
+		dev_err(&pdev->dev, "could not attach interrupt: %d\n", r);
+		goto probe_out2;
+	}
+
+	__ssp_add_console_port(ssp);
+
+	r = uart_add_one_port(&sifive_serial_uart_driver, &ssp->port);
+	if (r != 0) {
+		dev_err(&pdev->dev, "could not add uart: %d\n", r);
+		goto probe_out3;
+	}
+
+	return 0;
+
+probe_out3:
+	__ssp_remove_console_port(ssp);
+	free_irq(ssp->port.irq, ssp);
+probe_out2:
+	clk_notifier_unregister(ssp->clk, &ssp->clk_notifier);
+probe_out1:
+	return r;
+}
+
+static int sifive_serial_remove(struct platform_device *dev)
+{
+	struct sifive_serial_port *ssp = platform_get_drvdata(dev);
+
+	__ssp_remove_console_port(ssp);
+	uart_remove_one_port(&sifive_serial_uart_driver, &ssp->port);
+	free_irq(ssp->port.irq, ssp);
+	clk_notifier_unregister(ssp->clk, &ssp->clk_notifier);
+
+	return 0;
+}
+
+static const struct of_device_id sifive_serial_of_match[] = {
+	{ .compatible = "sifive,fu540-c000-uart0" },
+	{ .compatible = "sifive,uart0" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sifive_serial_of_match);
+
+static struct platform_driver sifive_serial_platform_driver = {
+	.probe		= sifive_serial_probe,
+	.remove		= sifive_serial_remove,
+	.driver		= {
+		.name	= SIFIVE_SERIAL_NAME,
+		.of_match_table = of_match_ptr(sifive_serial_of_match),
+	},
+};
+
+static int __init sifive_serial_init(void)
+{
+	int r;
+
+	r = uart_register_driver(&sifive_serial_uart_driver);
+	if (r)
+		goto init_out1;
+
+	r = platform_driver_register(&sifive_serial_platform_driver);
+	if (r)
+		goto init_out2;
+
+	return 0;
+
+init_out2:
+	uart_unregister_driver(&sifive_serial_uart_driver);
+init_out1:
+	return r;
+}
+
+static void __exit sifive_serial_exit(void)
+{
+	platform_driver_unregister(&sifive_serial_platform_driver);
+	uart_unregister_driver(&sifive_serial_uart_driver);
+}
+
+module_init(sifive_serial_init);
+module_exit(sifive_serial_exit);
+
+MODULE_DESCRIPTION("SiFive UART serial driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul Walmsley <paul@pwsan.com>");
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index 6009ee2c2e99..2191fa691770 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -287,4 +287,7 @@
 /* RDA UART */
 #define PORT_RDA	118
 
+/* SiFive UART */
+#define PORT_SIFIVE_V0	119
+
 #endif /* _UAPILINUX_SERIAL_CORE_H */
-- 
2.20.1


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Re: [PATCH v5 2/2] tty: serial: add driver for the SiFive UART

[Kevin Hilman]

Paul Walmsley <paul.walmsley@sifive.com> writes:

> Add a serial driver for the SiFive UART, found on SiFive FU540 devices
> (among others).
>
> The underlying serial IP block is relatively basic, and currently does
> not support serial break detection.  Further information on the IP
> block can be found in the documentation and Chisel sources:
>
>     https://static.dev.sifive.com/FU540-C000-v1.0.pdf
>
>     https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/uart
>
> This driver was written in collaboration with Wesley Terpstra
> <wesley@sifive.com>.
>
> Tested on a SiFive HiFive Unleashed A00 board, using BBL and the open-
> source FSBL (using a DT file based on what's targeted for mainline).
>
> This revision incorporates changes based on comments by Julia Lawall
> <julia.lawall@lip6.fr>, Emil Renner Berthing <kernel@esmil.dk>, and
> Andreas Schwab <schwab@suse.de>.  Thanks also to Andreas for testing
> the driver with his userspace and reporting a bug with the
> set_termios implementation.
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> Signed-off-by: Paul Walmsley <paul@pwsan.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.com>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Wesley Terpstra <wesley@sifive.com>
> Cc: linux-serial@vger.kernel.org
> Cc: linux-riscv@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: Julia Lawall <julia.lawall@lip6.fr>
> Cc: Emil Renner Berthing <kernel@esmil.dk>
> Cc: Andreas Schwab <schwab@suse.de>

Tested-by: Kevin Hilman <khilman@baylibre.com>

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Kevin Hilman]

Hi Paul,

Paul Walmsley <paul.walmsley@sifive.com> writes:

> This series adds a serial driver, with console support, for the
> UART IP block present on the SiFive FU540 SoC.  The programming
> model is straightforward, but unique.
>
> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
> open-source FSBL (with appropriate patches to the DT data).
>
> This fifth version fixes a bug in the set_termios handler,
> found by Andreas Schwab <schwab@suse.de>.
>
> The patches in this series can also be found, with the PRCI patches,
> DT patches, and DT prerequisite patch, at:
>
> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4

I tried this branch, and it doesn't boot on my unleashed board.

Here's the boot log when I pass the DT built from your branch via
u-boot: https://termbin.com/rfp3.

I also tried the same thing, but using the DT that's hard-coded into
SBI/u-boot.  That doesn't boot fully either[1], but one thing I noted is
that with the DT from the kernel tree, the printk timestamps aren't
moving.  Maybe I'm still missing some kconfig options to enable the
right clock and/or IRQ controllers? I'm using this fragment[2] on top of
the default defconfig (arch/riscv/configs/defconfig).

Could you share the defconfig you're using when testing your branch?

Also for reference, I'm able to successfully build/boot the
5.1-rc1-unleashed branch from Atish's tree[3] using that kconfig
fragment[2] (and the hard-coded DT from u-boot/SBI).  Full log here[4].

Thanks,

Kevin

[1] https://termbin.com/wuc9
[2]
CONFIG_CLK_SIFIVE=y
CONFIG_CLK_SIFIVE_FU540_PRCI=y

CONFIG_SERIAL_SIFIVE=y
CONFIG_SERIAL_SIFIVE_CONSOLE=y

CONFIG_SIFIVE_PLIC=y
CONFIG_SPI=y
CONFIG_SPI_SIFIVE=y
CONFIG_GPIOLIB=y
CONFIG_GPIO_SIFIVE=y
CONFIG_PWM_SIFIVE=y

CONFIG_CLK_U54_PRCI=y
CONFIG_CLK_GEMGXL_MGMT=y

[3] https://github.com/atishp04/linux/tree/5.1-rc1-unleashed
[4] https://termbin.com/12bg

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Atish Patra]

On 4/18/19 4:22 PM, Kevin Hilman wrote:
> Hi Paul,
> 
> Paul Walmsley <paul.walmsley@sifive.com> writes:
> 
>> This series adds a serial driver, with console support, for the
>> UART IP block present on the SiFive FU540 SoC.  The programming
>> model is straightforward, but unique.
>>
>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
>> open-source FSBL (with appropriate patches to the DT data).
>>
>> This fifth version fixes a bug in the set_termios handler,
>> found by Andreas Schwab <schwab@suse.de>.
>>
>> The patches in this series can also be found, with the PRCI patches,
>> DT patches, and DT prerequisite patch, at:
>>
>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4
> 
> I tried this branch, and it doesn't boot on my unleashed board.
> 
> Here's the boot log when I pass the DT built from your branch via
> u-boot: https://termbin.com/rfp3.
> 

Unfortunately, that won't work. The current DT modifications by OpenSBI.

1. Change hart status to "masked" from "okay".
2. M-mode interrupt masking in PLIC node.
3. Add a chosen node for serial access in U-Boot.

You can ignore 3 for your use case. However, if you pass a dtb built 
from source code, that will have hart0 enabled and M-mode interrupts 
enabled in DT.

Not sure if we should do these DT modifications in U-Boot as well.

I also noticed that your kernel is booting only 1 hart.
Just FYI: RISC-V SMP for U-Boot patches are merged in master. So you 
should be able to boot all cpus. You can ingore FU540_ENABLED_HART_MASK 
in OpenSBI build as well.

Regards,
Atish
> I also tried the same thing, but using the DT that's hard-coded into
> SBI/u-boot.  That doesn't boot fully either[1], but one thing I noted is
> that with the DT from the kernel tree, the printk timestamps aren't
> moving.  Maybe I'm still missing some kconfig options to enable the
> right clock and/or IRQ controllers? I'm using this fragment[2] on top of
> the default defconfig (arch/riscv/configs/defconfig).
> 
> Could you share the defconfig you're using when testing your branch?
> 
> Also for reference, I'm able to successfully build/boot the
> 5.1-rc1-unleashed branch from Atish's tree[3] using that kconfig
> fragment[2] (and the hard-coded DT from u-boot/SBI).  Full log here[4].
> 
> Thanks,
> 
> Kevin
> 
> [1] https://termbin.com/wuc9
> [2]
> CONFIG_CLK_SIFIVE=y
> CONFIG_CLK_SIFIVE_FU540_PRCI=y
> 
> CONFIG_SERIAL_SIFIVE=y
> CONFIG_SERIAL_SIFIVE_CONSOLE=y
> 
> CONFIG_SIFIVE_PLIC=y
> CONFIG_SPI=y
> CONFIG_SPI_SIFIVE=y
> CONFIG_GPIOLIB=y
> CONFIG_GPIO_SIFIVE=y
> CONFIG_PWM_SIFIVE=y
> 
> CONFIG_CLK_U54_PRCI=y
> CONFIG_CLK_GEMGXL_MGMT=y
> 
> [3] https://github.com/atishp04/linux/tree/5.1-rc1-unleashed
> [4] https://termbin.com/12bg
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 


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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Kevin Hilman]

Atish Patra <atish.patra@wdc.com> writes:

> On 4/18/19 4:22 PM, Kevin Hilman wrote:
>> Hi Paul,
>> 
>> Paul Walmsley <paul.walmsley@sifive.com> writes:
>> 
>>> This series adds a serial driver, with console support, for the
>>> UART IP block present on the SiFive FU540 SoC.  The programming
>>> model is straightforward, but unique.
>>>
>>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
>>> open-source FSBL (with appropriate patches to the DT data).
>>>
>>> This fifth version fixes a bug in the set_termios handler,
>>> found by Andreas Schwab <schwab@suse.de>.
>>>
>>> The patches in this series can also be found, with the PRCI patches,
>>> DT patches, and DT prerequisite patch, at:
>>>
>>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4
>> 
>> I tried this branch, and it doesn't boot on my unleashed board.
>> 
>> Here's the boot log when I pass the DT built from your branch via
>> u-boot: https://termbin.com/rfp3.
>> 
>
> Unfortunately, that won't work. The current DT modifications by OpenSBI.
>
> 1. Change hart status to "masked" from "okay".
> 2. M-mode interrupt masking in PLIC node.
> 3. Add a chosen node for serial access in U-Boot.
>
> You can ignore 3 for your use case. However, if you pass a dtb built 
> from source code, that will have hart0 enabled and M-mode interrupts 
> enabled in DT.

Hmm, so what you're saying is there not currently any way to pass a DT
built from source using OpenSBI + mainline u-boot?

As a short-term workaround, is there a way to make these changes from
the u-boot command-line after loading a DTB built from source into
memory?  If so, I could at least script that part.


> Not sure if we should do these DT modifications in U-Boot as well.

I guess so (and I'd be happy to test the patch.)

Either that, or the upstream DTs (or code) should have those features to
the right settings.

Speaking of which, I tried to patch the DT from Paul's recent series[1]
to make the necessary changes.  I can see where to change cpu0 from
"okay" to "masked", but I'm not so sure how to make the PLIC change.

I was hoping to be able to review/test Paul's DT patches, but now I'm a
bit confused as to how to do that.

> I also noticed that your kernel is booting only 1 hart.
> Just FYI: RISC-V SMP for U-Boot patches are merged in master. So you 
> should be able to boot all cpus. You can ingore FU540_ENABLED_HART_MASK 
> in OpenSBI build as well.

Ah, nice.

I've just updated to u-boot master branch with SMP enabled, and build a
new openSBI (also from master branch) with u-boot payload. Using your
v5.1-rc4_unleashed branch, I see 4 CPUs booting:
https://termbin.com/kg13

Thanks,

Kevin

[1] https://lore.kernel.org/lkml/20190413020111.23400-1-paul.walmsley@sifive.com/T/#m77daa2857b76ec7cbca0672ad03ae286f61ca0e6

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Atish Patra]

On 4/19/19 12:18 PM, Kevin Hilman wrote:
> Atish Patra <atish.patra@wdc.com> writes:
> 
>> On 4/18/19 4:22 PM, Kevin Hilman wrote:
>>> Hi Paul,
>>>
>>> Paul Walmsley <paul.walmsley@sifive.com> writes:
>>>
>>>> This series adds a serial driver, with console support, for the
>>>> UART IP block present on the SiFive FU540 SoC.  The programming
>>>> model is straightforward, but unique.
>>>>
>>>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
>>>> open-source FSBL (with appropriate patches to the DT data).
>>>>
>>>> This fifth version fixes a bug in the set_termios handler,
>>>> found by Andreas Schwab <schwab@suse.de>.
>>>>
>>>> The patches in this series can also be found, with the PRCI patches,
>>>> DT patches, and DT prerequisite patch, at:
>>>>
>>>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4
>>>
>>> I tried this branch, and it doesn't boot on my unleashed board.
>>>
>>> Here's the boot log when I pass the DT built from your branch via
>>> u-boot: https://termbin.com/rfp3.
>>>
>>
>> Unfortunately, that won't work. The current DT modifications by OpenSBI.
>>
>> 1. Change hart status to "masked" from "okay".
>> 2. M-mode interrupt masking in PLIC node.
>> 3. Add a chosen node for serial access in U-Boot.
>>
>> You can ignore 3 for your use case. However, if you pass a dtb built
>> from source code, that will have hart0 enabled and M-mode interrupts
>> enabled in DT.
> 
> Hmm, so what you're saying is there not currently any way to pass a DT
> built from source using OpenSBI + mainline u-boot?
> 

OpenSBI can accept DT built from source with following build option.

FW_PAYLOAD_FDT="<unleashed>.dtb"

More documentation:
https://github.com/riscv/opensbi/blob/master/docs/firmware/fw_payload.md

> As a short-term workaround, is there a way to make these changes from
> the u-boot command-line after loading a DTB built from source into
> memory?  If so, I could at least script that part.
> 
> 
>> Not sure if we should do these DT modifications in U-Boot as well.
> 
> I guess so (and I'd be happy to test the patch.)
> 
> Either that, or the upstream DTs (or code) should have those features to
> the right settings.
> 
> Speaking of which, I tried to patch the DT from Paul's recent series[1]
> to make the necessary changes.  I can see where to change cpu0 from
> "okay" to "masked", but I'm not so sure how to make the PLIC change.
> 

Here is the code snippet of how OpenSBI modifies the DT.

https://github.com/riscv/opensbi/blob/master/platform/sifive/fu540/platform.c#L53

If you just want to use custom built DTB, you can use OpenSBI build 
option instead of scripting these.

We don't want OpenSBI to keep modifying the DT forever. But we have to 
do it until there is a better solution available.

> I was hoping to be able to review/test Paul's DT patches, but now I'm a
> bit confused as to how to do that.
> 
>> I also noticed that your kernel is booting only 1 hart.
>> Just FYI: RISC-V SMP for U-Boot patches are merged in master. So you
>> should be able to boot all cpus. You can ingore FU540_ENABLED_HART_MASK
>> in OpenSBI build as well.
> 
> Ah, nice.
> 
> I've just updated to u-boot master branch with SMP enabled, and build a
> new openSBI (also from master branch) with u-boot payload. Using your
> v5.1-rc4_unleashed branch, I see 4 CPUs booting:
> https://termbin.com/kg13
> 

Great.

Regards,
Atish
> Thanks,
> 
> Kevin
> 
> [1] https://lore.kernel.org/lkml/20190413020111.23400-1-paul.walmsley@sifive.com/T/#m77daa2857b76ec7cbca0672ad03ae286f61ca0e6
> 


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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Kevin Hilman]

Atish Patra <atish.patra@wdc.com> writes:

> On 4/19/19 12:18 PM, Kevin Hilman wrote:
>> Atish Patra <atish.patra@wdc.com> writes:
>> 
>>> On 4/18/19 4:22 PM, Kevin Hilman wrote:
>>>> Hi Paul,
>>>>
>>>> Paul Walmsley <paul.walmsley@sifive.com> writes:
>>>>
>>>>> This series adds a serial driver, with console support, for the
>>>>> UART IP block present on the SiFive FU540 SoC.  The programming
>>>>> model is straightforward, but unique.
>>>>>
>>>>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
>>>>> open-source FSBL (with appropriate patches to the DT data).
>>>>>
>>>>> This fifth version fixes a bug in the set_termios handler,
>>>>> found by Andreas Schwab <schwab@suse.de>.
>>>>>
>>>>> The patches in this series can also be found, with the PRCI patches,
>>>>> DT patches, and DT prerequisite patch, at:
>>>>>
>>>>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4
>>>>
>>>> I tried this branch, and it doesn't boot on my unleashed board.
>>>>
>>>> Here's the boot log when I pass the DT built from your branch via
>>>> u-boot: https://termbin.com/rfp3.
>>>>
>>>
>>> Unfortunately, that won't work. The current DT modifications by OpenSBI.
>>>
>>> 1. Change hart status to "masked" from "okay".
>>> 2. M-mode interrupt masking in PLIC node.
>>> 3. Add a chosen node for serial access in U-Boot.
>>>
>>> You can ignore 3 for your use case. However, if you pass a dtb built
>>> from source code, that will have hart0 enabled and M-mode interrupts
>>> enabled in DT.
>> 
>> Hmm, so what you're saying is there not currently any way to pass a DT
>> built from source using OpenSBI + mainline u-boot?
>> 
>
> OpenSBI can accept DT built from source with following build option.
>
> FW_PAYLOAD_FDT="<unleashed>.dtb"
>
> More documentation:
> https://github.com/riscv/opensbi/blob/master/docs/firmware/fw_payload.md

I'm aware of that method, but I'm looking for a way that doesn't require
me to rebuild/reflash SBI every time.

Basically, I want u-boot to TFTP the DTB (along with kernel and ramdisk)
and boot it from memory.

On all other DT platforms in kernelCI, we build DTB(s) along with the
kernel (but not built into the kernel.)  We then use the bootloader to
load the kernel, DTB and ramdisk that we built.

>> As a short-term workaround, is there a way to make these changes from
>> the u-boot command-line after loading a DTB built from source into
>> memory?  If so, I could at least script that part.
>> 
>> 
>>> Not sure if we should do these DT modifications in U-Boot as well.
>> 
>> I guess so (and I'd be happy to test the patch.)
>> 
>> Either that, or the upstream DTs (or code) should have those features to
>> the right settings.
>> 
>> Speaking of which, I tried to patch the DT from Paul's recent series[1]
>> to make the necessary changes.  I can see where to change cpu0 from
>> "okay" to "masked", but I'm not so sure how to make the PLIC change.
>> 
>
> Here is the code snippet of how OpenSBI modifies the DT.
>
> https://github.com/riscv/opensbi/blob/master/platform/sifive/fu540/platform.c#L53

Thanks, based on that, I was able to modify the DTB I'm builing from
source[1], but it still doesn't fully boot.

Looks like Paul has so far only tested this with BBL + FSBL, so I think
I'll wait to hear from him how that setup might be different from using
OpenSBI + u-boot.

Thanks for all the help,

Kevin

[1]
diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
index dd3b9395cedf..299398c4201d 100644
--- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
+++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
@@ -30,7 +30,7 @@
                        i-cache-size = <16384>;
                        reg = <0>;
                        riscv,isa = "rv64imac";
-                       status = "okay";
+                       status = "masked";
                        cpu0_intc: interrupt-controller {
                                #interrupt-cells = <1>;
                                compatible = "riscv,cpu-intc";
@@ -148,11 +148,11 @@
                        reg = <0x0 0xc000000 0x0 0x4000000>;
                        interrupt-controller;
                        interrupts-extended = <
-                               &cpu0_intc 11
-                               &cpu1_intc 11 &cpu1_intc 9
-                               &cpu2_intc 11 &cpu2_intc 9
-                               &cpu3_intc 11 &cpu3_intc 9
-                               &cpu4_intc 11 &cpu4_intc 9>;
+                               &cpu0_intc 0xffffffff
+                               &cpu1_intc 0xffffffff &cpu1_intc 9
+                               &cpu2_intc 0xffffffff &cpu2_intc 9
+                               &cpu3_intc 0xffffffff &cpu3_intc 9
+                               &cpu4_intc 0xffffffff &cpu4_intc 9>;
                };
                prci: clock-controller@10000000 {
                        compatible = "sifive,fu540-c000-prci";

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Paul Walmsley]

On Fri, 19 Apr 2019, Kevin Hilman wrote:

> Looks like Paul has so far only tested this with BBL + FSBL, so I think
> I'll wait to hear from him how that setup might be different from using
> OpenSBI + u-boot.

I'd recommend testing the DT patches with BBL and the open-source FSBL.  
That's the traditional way of booting RISC-V Linux systems.

The goal is to transition to U-Boot over time.  However, right now the 
U-boot port is still new.  It wouldn't surprise me if we need to modify 
the kernel, U-boot, or the SBI layers as part of that process.  In the 
short term, we need to get some sort of baseline DT data in place before 
more chips and boards start showing up.

I'll post a separate message with details on how to reproduce the test 
setup that I'm using.


- Paul

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Kevin Hilman]

Paul Walmsley <paul.walmsley@sifive.com> writes:

> On Fri, 19 Apr 2019, Kevin Hilman wrote:
>
>> Looks like Paul has so far only tested this with BBL + FSBL, so I think
>> I'll wait to hear from him how that setup might be different from using
>> OpenSBI + u-boot.
>
> I'd recommend testing the DT patches with BBL and the open-source FSBL.  
> That's the traditional way of booting RISC-V Linux systems.

OK, but as you know, not the tradiaional way of booting most other linux
systems.  ;)

I'm working on getting RISC-V supported in kernelCI in a fully-automated
way, and I don't currently have the time to add add support for BBL+FSBL
to kernelCI automation tooling, so having u-boot support is the best way
to get support in kernelCI, IMO.

Kevin

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Paul Walmsley]

On Thu, 2 May 2019, Kevin Hilman wrote:

> Paul Walmsley <paul.walmsley@sifive.com> writes:
> 
> > I'd recommend testing the DT patches with BBL and the open-source FSBL.  
> > That's the traditional way of booting RISC-V Linux systems.
> 
> OK, but as you know, not the tradiaional way of booting most other linux
> systems.  ;)
> 
> I'm working on getting RISC-V supported in kernelCI in a fully-automated
> way, and I don't currently have the time to add add support for BBL+FSBL
> to kernelCI automation tooling, so having u-boot support is the best way
> to get support in kernelCI, IMO.

That's great.  Please keep hacking away on RISC-V support for kernelCI.  
My point is just that the U-boot and OpenSBI software stack you're working 
with is not going to be useful for automatic tests of some kernel patches 
yet.  That stack is still very new, and was written around a non-upstream 
set of DT data.  We are in the process of posting and merging patches to 
fix that, but it's going to take a few releases of both the kernel and 
those other boot stack components until things are sorted out in a more 
durable way.


- Paul

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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Paul Walmsley]

Hi Kevin,

On Fri, 19 Apr 2019, Kevin Hilman wrote:
> Atish Patra <atish.patra@wdc.com> writes:
> > On 4/18/19 4:22 PM, Kevin Hilman wrote:
> >> Paul Walmsley <paul.walmsley@sifive.com> writes:
> >> 
> >>> This series adds a serial driver, with console support, for the
> >>> UART IP block present on the SiFive FU540 SoC.  The programming
> >>> model is straightforward, but unique.
> >>>
> >>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
> >>> open-source FSBL (with appropriate patches to the DT data).
> >>>
> >>> This fifth version fixes a bug in the set_termios handler,
> >>> found by Andreas Schwab <schwab@suse.de>.
> >>>
> >>> The patches in this series can also be found, with the PRCI patches,
> >>> DT patches, and DT prerequisite patch, at:
> >>>
> >>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4

...

> I've just updated to u-boot master branch with SMP enabled, and build a
> new openSBI (also from master branch) with u-boot payload. Using your
> v5.1-rc4_unleashed branch, I see 4 CPUs booting:
> https://termbin.com/kg13

Now that the serial driver is working for you, care to send a Tested-by: ?


thanks,

- Paul


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Re: [PATCH v5 0/2] tty: serial: add DT bindings and serial driver for the SiFive FU540 UART

[Loys Ollivier]

On Thu 18 Apr 2019 at 18:04, Atish Patra <atish.patra@wdc.com> wrote:

> On 4/18/19 4:22 PM, Kevin Hilman wrote:
>> Hi Paul,
>>
>> Paul Walmsley <paul.walmsley@sifive.com> writes:
>>
>>> This series adds a serial driver, with console support, for the
>>> UART IP block present on the SiFive FU540 SoC.  The programming
>>> model is straightforward, but unique.
>>>
>>> Boot-tested on a SiFive FU540 HiFive-U board, using BBL and the
>>> open-source FSBL (with appropriate patches to the DT data).
>>>
>>> This fifth version fixes a bug in the set_termios handler,
>>> found by Andreas Schwab <schwab@suse.de>.
>>>
>>> The patches in this series can also be found, with the PRCI patches,
>>> DT patches, and DT prerequisite patch, at:
>>>
>>> https://github.com/sifive/riscv-linux/tree/dev/paulw/serial-v5.1-rc4
>>
>> I tried this branch, and it doesn't boot on my unleashed board.
>>
>> Here's the boot log when I pass the DT built from your branch via
>> u-boot: https://termbin.com/rfp3.
>>
>
> Unfortunately, that won't work. The current DT modifications by OpenSBI.
>
> 1. Change hart status to "masked" from "okay".
> 2. M-mode interrupt masking in PLIC node.
> 3. Add a chosen node for serial access in U-Boot.
>
> You can ignore 3 for your use case. However, if you pass a dtb built from source
> code, that will have hart0 enabled and M-mode interrupts enabled in DT.

Atish,
I'm trying to get the kernel boot with the current linux kernel DT from
Paul's patch series [0].

Could you point me to some documentation on 2. ?
Or do you know of a way to disable M-mode interrupts from U-boot ?

[0]: https://lore.kernel.org/patchwork/project/lkml/list/?series=390077

Thanks,
Loys

>
> Not sure if we should do these DT modifications in U-Boot as well.
>

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