Re: [U-Boot] [PATCH 1/2] drivers: serial: Add SiFive UART driver

On Sat, Dec 8, 2018 at 12:10 AM Palmer Dabbelt palmer@sifive.com wrote:

On Tue, 04 Dec 2018 22:29:23 PST (-0800), anup@brainfault.org wrote:

...

This patch adds SiFive UART driver. The driver is 100% DM driver and it determines input clock using clk framework.

Signed-off-by: Anup Patel anup@brainfault.org

drivers/serial/Kconfig | 13 +++ drivers/serial/Makefile | 1 + drivers/serial/serial_sifive.c | 193 +++++++++++++++++++++++++++++++++ 3 files changed, 207 insertions(+) create mode 100644 drivers/serial/serial_sifive.c

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index 3bcc61e731..30f7e00557 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -343,6 +343,13 @@ config DEBUG_UART_SANDBOX start up driver model. The driver will be available until the real driver model serial is running.

+config DEBUG_UART_SIFIVE

• bool "SiFive UART"
  

• help
  

•   Select this to enable a debug UART using the serial_sifive driver. You
  

•   will need to provide parameters to make this work. The driver will
  

•   be available until the real driver-model serial is running.
  

config DEBUG_UART_STM32 bool "STMicroelectronics STM32" depends on STM32_SERIAL @@ -685,6 +692,12 @@ config PXA_SERIAL If you have a machine based on a Marvell XScale PXA2xx CPU you can enable its onboard serial ports by enabling this option.

+config SIFIVE_SERIAL

• bool "SiFive UART support"
  

• depends on DM_SERIAL
  

• help
  

•   This driver supports the SiFive UART. If unsure say N.
  

config STI_ASC_SERIAL bool "STMicroelectronics on-chip UART" depends on DM_SERIAL && ARCH_STI diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile index b6377b1076..b6781535a8 100644 --- a/drivers/serial/Makefile +++ b/drivers/serial/Makefile @@ -68,6 +68,7 @@ obj-$(CONFIG_NULLDEV_SERIAL) += serial_nulldev.o obj-$(CONFIG_OWL_SERIAL) += serial_owl.o obj-$(CONFIG_OMAP_SERIAL) += serial_omap.o obj-$(CONFIG_MTK_SERIAL) += serial_mtk.o +obj-$(CONFIG_SIFIVE_SERIAL) += serial_sifive.o

ifndef CONFIG_SPL_BUILD obj-$(CONFIG_USB_TTY) += usbtty.o diff --git a/drivers/serial/serial_sifive.c b/drivers/serial/serial_sifive.c new file mode 100644 index 0000000000..cce05d5a01 --- /dev/null +++ b/drivers/serial/serial_sifive.c @@ -0,0 +1,193 @@ +// SPDX-License-Identifier: GPL-2.0+ +/*

• • Copyright (C) 2012 Michal Simek monstr@monstr.eu
• • Copyright (C) 2011-2012 Xilinx, Inc. All rights reserved.
• */

+#include <clk.h> +#include <common.h> +#include <debug_uart.h> +#include <dm.h> +#include <errno.h> +#include <fdtdec.h> +#include <watchdog.h> +#include <asm/io.h> +#include <linux/compiler.h> +#include <serial.h>

+DECLARE_GLOBAL_DATA_PTR;

+#define UART_TXFIFO_FULL 0x80000000 +#define UART_RXFIFO_EMPTY 0x80000000 +#define UART_RXFIFO_DATA 0x000000ff +#define UART_TXCTRL_TXEN 0x1 +#define UART_RXCTRL_RXEN 0x1

+struct uart_sifive {

• u32 txfifo;
  

• u32 rxfifo;
  

• u32 txctrl;
  

• u32 rxctrl;
  

• u32 ie;
  

• u32 ip;
  

• u32 div;
  

+};

+struct sifive_uart_platdata {

• unsigned int clock;
  

• struct uart_sifive *regs;
  

+};

+/* Set up the baud rate in gd struct */ +static void _sifive_serial_setbrg(struct uart_sifive *regs,

•                           unsigned long clock, unsigned long baud)
  

+{

• writel((u32)((clock / baud) - 1), &regs->div);
  

+}

+static void _sifive_serial_init(struct uart_sifive *regs) +{

• writel(UART_TXCTRL_TXEN, &regs->txctrl);
  

• writel(UART_RXCTRL_RXEN, &regs->rxctrl);
  

• writel(0, &regs->ie);
  

+}

+static int _sifive_serial_putc(struct uart_sifive *regs, const char c) +{

• if (readl(&regs->txfifo) & UART_TXFIFO_FULL)
  

•         return -EAGAIN;
  

• writel(c, &regs->txfifo);
  

• return 0;
  

+}

+static int _sifive_serial_getc(struct uart_sifive *regs) +{

• int ch = readl(&regs->rxfifo);
  

• if (ch & UART_RXFIFO_EMPTY)
  

•         return -EAGAIN;
  

• ch &= UART_RXFIFO_DATA;
  

• return (!ch) ? -EAGAIN : ch;
  

+}

+static int sifive_serial_setbrg(struct udevice *dev, int baudrate) +{

• int err;
  

• struct clk clk;
  

• struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
  

• err = clk_get_by_index(dev, 0, &clk);
  

• if (!err) {
  

•         err = clk_get_rate(&clk);
  

•         if (!IS_ERR_VALUE(err))
  

•                 platdata->clock = err;
  

• } else if (err != -ENOENT && err != -ENODEV && err != -ENOSYS) {
  

•         debug("SiFive UART failed to get clock\n");
  

•         return err;
  

• }
  

• if (!platdata->clock)
  

•         platdata->clock = dev_read_u32_default(dev, "clock-frequency", 0);
  

• if (!platdata->clock) {
  

•         debug("SiFive UART clock not defined\n");
  

•         return -EINVAL;
  

• }
  

• _sifive_serial_setbrg(platdata->regs, platdata->clock, baudrate);
  

• return 0;
  

+}

I don't see anything that ensures the TX FIFO is drained before changing the baud rate. I don't know anything about u-boot so I'm not sure if that's expected.

Ohh yes, u-boot serial drivers usually don't drain TX FIFO.

If required we can add it via separate patch.

...

+static int sifive_serial_probe(struct udevice *dev) +{

• struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
  

• /* No need to reinitialize the UART after relocation */
  

• if (gd->flags & GD_FLG_RELOC)
  

•         return 0;
  

• _sifive_serial_init(platdata->regs);
  

• return 0;
  

+}

+static int sifive_serial_getc(struct udevice *dev) +{

• int c;
  

• struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
  

• struct uart_sifive *regs = platdata->regs;
  

• while ((c = _sifive_serial_getc(regs)) == -EAGAIN) ;
  

• return c;
  

+}

+static int sifive_serial_putc(struct udevice *dev, const char ch) +{

• int rc;
  

• struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
  

• while ((rc = _sifive_serial_putc(platdata->regs, ch)) == -EAGAIN) ;
  

• return rc;
  

+}

+static int sifive_serial_ofdata_to_platdata(struct udevice *dev) +{

• struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
  

• platdata->regs = (struct uart_sifive *)dev_read_addr(dev);
  

• if (IS_ERR(platdata->regs))
  

•         return PTR_ERR(platdata->regs);
  

• return 0;
  

+}

+static const struct dm_serial_ops sifive_serial_ops = {

• .putc = sifive_serial_putc,
  

• .getc = sifive_serial_getc,
  

• .setbrg = sifive_serial_setbrg,
  

+};

+static const struct udevice_id sifive_serial_ids[] = {

• { .compatible = "sifive,uart0" },
  

• { }
  

+};

+U_BOOT_DRIVER(serial_sifive) = {

• .name   = "serial_sifive",
  

• .id     = UCLASS_SERIAL,
  

• .of_match = sifive_serial_ids,
  

• .ofdata_to_platdata = sifive_serial_ofdata_to_platdata,
  

• .platdata_auto_alloc_size = sizeof(struct sifive_uart_platdata),
  

• .probe = sifive_serial_probe,
  

• .ops    = &sifive_serial_ops,
  

• .priv_auto_alloc_size   = sizeof(struct sifive_uart_platdata),
  

+};

+#ifdef CONFIG_DEBUG_UART_SIFIVE +static inline void _debug_uart_init(void) +{

• struct uart_sifive *regs =
  

•                 (struct uart_sifive *)CONFIG_DEBUG_UART_BASE;
  

• _sifive_serial_setbrg(regs, CONFIG_DEBUG_UART_CLOCK,
  

•                       CONFIG_BAUDRATE);
  

• _sifive_serial_init(regs);
  

+}

+static inline void _debug_uart_putc(int ch) +{

• struct uart_sifive *regs =
  

•                 (struct uart_sifive *)CONFIG_DEBUG_UART_BASE;
  

• while (_sifive_serial_putc(regs, ch) == -EAGAIN)
  

•         WATCHDOG_RESET();
  

+}

+DEBUG_UART_FUNCS

+#endif

Reviewed-by: Palmer Dabbelt palmer@sifive.com

Thanks, Anup