[RFCv2 1/2] serial: add driver for SiFive UART

[Antony Pavlov]

On Thu, 17 Nov 2016 08:07:06 +0100
Sascha Hauer <s.hauer at pengutronix.de> wrote:

> On Mon, Nov 14, 2016 at 12:50:14AM +0300, Antony Pavlov wrote:
> > Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
> > ---
> > 
> > TODO:
> > 
> >   * add speed setup support.
> > 
> >  drivers/serial/Kconfig         |   3 ++
> >  drivers/serial/Makefile        |   1 +
> >  drivers/serial/serial_sifive.c | 109 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 113 insertions(+)
> > 
> > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> > index b112d7e..70509b9 100644
> > --- a/drivers/serial/Kconfig
> > +++ b/drivers/serial/Kconfig
> > @@ -117,6 +117,9 @@ config DRIVER_SERIAL_S3C_AUTOSYNC
> >  	  Say Y here if you want to use the auto flow feature of this
> >  	  UART. RTS and CTS will be handled by the hardware when enabled.
> >  
> > +config DRIVER_SERIAL_SIFIVE
> > +	bool "SiFive serial driver"
> > +
> >  config DRIVER_SERIAL_PXA
> >  	bool "PXA serial driver"
> >  	depends on ARCH_PXA
> > diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
> > index 189e777..368e992 100644
> > --- a/drivers/serial/Makefile
> > +++ b/drivers/serial/Makefile
> > @@ -20,3 +20,4 @@ obj-$(CONFIG_DRIVER_SERIAL_AUART)		+= serial_auart.o
> >  obj-$(CONFIG_DRIVER_SERIAL_CADENCE)		+= serial_cadence.o
> >  obj-$(CONFIG_DRIVER_SERIAL_EFI_STDIO)		+= efi-stdio.o
> >  obj-$(CONFIG_DRIVER_SERIAL_DIGIC)		+= serial_digic.o
> > +obj-$(CONFIG_DRIVER_SERIAL_SIFIVE)		+= serial_sifive.o
> > diff --git a/drivers/serial/serial_sifive.c b/drivers/serial/serial_sifive.c
> > new file mode 100644
> > index 0000000..06e3521
> > --- /dev/null
> > +++ b/drivers/serial/serial_sifive.c
> > @@ -0,0 +1,109 @@
> > +/*
> > + * Copyright (C) 2016 Antony Pavlov <antonynpavlov at gmail.com>
> > + *
> > + * This file is part of barebox.
> > + * See file CREDITS for list of people who contributed to this project.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2
> > + * as published by the Free Software Foundation.
> > + *
> > + * 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.
> > + *
> > + */
> > +
> > +#include <common.h>
> > +#include <init.h>
> > +#include <malloc.h>
> > +#include <io.h>
> > +
> > +#define UART_RX_OFFSET 0
> > +#define UART_TX_OFFSET 0
> > +#define UART_TX_COUNT_OFFSET 0x4
> > +#define UART_RX_COUNT_OFFSET 0x8
> > +#define UART_DIVIDER_OFFSET  0xC
> > +
> > +static inline uint32_t sifive_serial_readl(struct console_device *cdev,
> > +						uint32_t offset)
> > +{
> > +	void __iomem *base = cdev->dev->priv;
> > +
> > +	return readl(base + offset);
> > +}
> > +
> > +static inline void sifive_serial_writel(struct console_device *cdev,
> > +					uint32_t value, uint32_t offset)
> > +{
> > +	void __iomem *base = cdev->dev->priv;
> > +
> > +	writel(value, base + offset);
> > +}
> > +
> > +static int sifive_serial_setbaudrate(struct console_device *cdev, int baudrate)
> > +{
> > +	/* FIXME: no baudrate setup at the momement :( */
> > +
> > +	return 0;
> > +}
> > +
> > +static void sifive_serial_putc(struct console_device *cdev, char c)
> > +{
> > +	sifive_serial_writel(cdev, c, UART_TX_OFFSET);
> > +}
> 
> This doesn't test if there is space in the FIFO. This is necessary, no?

Yes, you are right. I have to add 'check UART FIFO state' to the TODO list.
Current qemu-riscv SiFive UART model does not have transmit FIFO support
so I can't use it for tests.

I'm planning to run RISC-V barebox on real FPGA board in the nearest feature.
So baudrate setup code and FIFO state checking code will be added. 

-- 
Best regards,
  Antony Pavlov