Re: [PATCH v4 04/10] serial: bflb_uart: add Bouffalolab UART Driver

Jisheng Zhang
2023-05-31T14:22:34Z

On Tue, May 30, 2023 at 11:36:00AM +0100, Greg Kroah-Hartman wrote:
> On Thu, May 18, 2023 at 11:22:38PM +0800, Jisheng Zhang wrote:
> > Add the driver for Bouffalolab UART IP which is found in Bouffalolab
> > SoCs such as bl808.
>
> New uarts are being created that are NOT 8250-like? Why????

Hi,

I'm not sure I understand your meaning. I guess you mean writing the new
uart driver following 8250 style. And the latest example is
sunplus-uart.c, it can be used as an example how to write a 8250 style
driver for new non-8250 uart IP.

If the above guesses are wrong, could you please provide more details?

Thanks

>
>
> >
> > UART driver probe will create path named "/dev/ttySx".
> >
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> > drivers/tty/serial/Kconfig | 18 +
> > drivers/tty/serial/Makefile | 1 +
> > drivers/tty/serial/bflb_uart.c | 586 +++++++++++++++++++++++++++++++
> > include/uapi/linux/serial_core.h | 3 +
> > 4 files changed, 608 insertions(+)
> > create mode 100644 drivers/tty/serial/bflb_uart.c
> >
> > diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> > index 398e5aac2e77..abc30a0713f5 100644
> > --- a/drivers/tty/serial/Kconfig
> > +++ b/drivers/tty/serial/Kconfig
> > @@ -179,6 +179,24 @@ config SERIAL_ATMEL_TTYAT
> >
> > Say Y if you have an external 8250/16C550 UART. If unsure, say N.
> >
> > +config SERIAL_BFLB
> > + tristate "Bouffalolab serial port support"
> > + select SERIAL_CORE
> > + depends on COMMON_CLK
> > + help
> > + This enables the driver for the Bouffalolab's serial.
> > +
> > +config SERIAL_BFLB_CONSOLE
> > + bool "Support for console on Bouffalolab serial port"
> > + depends on SERIAL_BFLB=y
> > + select SERIAL_CORE_CONSOLE
> > + select SERIAL_EARLYCON
> > + help
> > + Say Y here if you wish to use a Bouffalolab UART 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) as /dev/ttySn.
> > +
> > config SERIAL_KGDB_NMI
> > bool "Serial console over KGDB NMI debugger port"
> > depends on KGDB_SERIAL_CONSOLE
> > diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
> > index cd9afd9e3018..5788a708d327 100644
> > --- a/drivers/tty/serial/Makefile
> > +++ b/drivers/tty/serial/Makefile
> > @@ -25,6 +25,7 @@ obj-$(CONFIG_SERIAL_8250) += 8250/
> >
> > obj-$(CONFIG_SERIAL_AMBA_PL010) += amba-pl010.o
> > obj-$(CONFIG_SERIAL_AMBA_PL011) += amba-pl011.o
> > +obj-$(CONFIG_SERIAL_BFLB) += bflb_uart.o
> > obj-$(CONFIG_SERIAL_CLPS711X) += clps711x.o
> > obj-$(CONFIG_SERIAL_PXA_NON8250) += pxa.o
> > obj-$(CONFIG_SERIAL_SA1100) += sa1100.o
> > diff --git a/drivers/tty/serial/bflb_uart.c b/drivers/tty/serial/bflb_uart.c
> > new file mode 100644
> > index 000000000000..3f80bba8599a
> > --- /dev/null
> > +++ b/drivers/tty/serial/bflb_uart.c
> > @@ -0,0 +1,586 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Based on bflb_uart.c, by Bouffalolab team
> > + *
> > + * Copyright (C) 2022 Jisheng Zhang <jszhang@kernel.org>
>
> It is 2023 :)
>
> > + */
> > +
> > +#include <linux/bitfield.h>
> > +#include <linux/clk.h>
> > +#include <linux/console.h>
> > +#include <linux/kernel.h>
> > +#include <linux/init.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/serial.h>
> > +#include <linux/serial_core.h>
> > +#include <linux/tty.h>
> > +#include <linux/tty_flip.h>
> > +
> > +#define UART_UTX_CONFIG 0x00
> > +#define UART_CR_UTX_EN BIT(0)
> > +#define UART_CR_UTX_CTS_EN BIT(1)
> > +#define UART_CR_UTX_FRM_EN BIT(2)
> > +#define UART_CR_UTX_PRT_EN BIT(4)
> > +#define UART_CR_UTX_PRT_SEL BIT(5)
> > +#define UART_CR_UTX_BIT_CNT_D_MSK GENMASK(10, 8)
> > +#define UART_CR_UTX_BIT_CNT_P_MSK GENMASK(12, 11)
> > +#define UART_URX_CONFIG 0x04
> > +#define UART_CR_URX_EN BIT(0)
> > +#define UART_CR_URX_PRT_EN BIT(4)
> > +#define UART_CR_URX_PRT_SEL BIT(5)
> > +#define UART_CR_URX_BIT_CNT_D_MSK GENMASK(10, 8)
> > +#define UART_BIT_PRD 0x08
> > +#define UART_CR_UTX_BIT_PRD_MSK GENMASK(15, 0)
> > +#define UART_CR_URX_BIT_PRD_MSK GENMASK(31, 16)
> > +#define UART_DATA_CONFIG 0x0c
> > +#define UART_CR_UART_BIT_INV BIT(0)
> > +#define UART_URX_RTO_TIMER 0x18
> > +#define UART_CR_URX_RTO_VALUE_MSK GENMASK(7, 0)
> > +#define UART_SW_MODE 0x1c
> > +#define UART_INT_STS 0x20
> > +#define UART_UTX_END_INT BIT(0)
> > +#define UART_URX_END_INT BIT(1)
> > +#define UART_UTX_FIFO_INT BIT(2)
> > +#define UART_URX_FIFO_INT BIT(3)
> > +#define UART_URX_RTO_INT BIT(4)
> > +#define UART_URX_PCE_INT BIT(5)
> > +#define UART_UTX_FER_INT BIT(6)
> > +#define UART_URX_FER_INT BIT(7)
> > +#define UART_URX_LSE_INT BIT(8)
> > +#define UART_INT_MASK 0x24
> > +#define UART_INT_CLEAR 0x28
> > +#define UART_INT_EN 0x2c
> > +#define UART_STATUS 0x30
> > +#define UART_STS_UTX_BUS_BUSY BIT(0)
> > +#define UART_FIFO_CONFIG_0 0x80
> > +#define UART_DMA_TX_EN BIT(0)
> > +#define UART_DMA_RX_EN BIT(1)
> > +#define UART_TX_FIFO_CLR BIT(2)
> > +#define UART_RX_FIFO_CLR BIT(3)
> > +#define UART_TX_FIFO_OVERFLOW BIT(4)
> > +#define UART_TX_FIFO_UNDERFLOW BIT(5)
> > +#define UART_RX_FIFO_OVERFLOW BIT(6)
> > +#define UART_RX_FIFO_UNDERFLOW BIT(7)
> > +#define UART_FIFO_CONFIG_1 0x84
> > +#define UART_TX_FIFO_CNT_MSK GENMASK(5, 0)
> > +#define UART_RX_FIFO_CNT_MSK GENMASK(13, 8)
> > +#define UART_TX_FIFO_TH_MSK GENMASK(20, 16)
> > +#define UART_RX_FIFO_TH_MSK GENMASK(28, 24)
> > +#define UART_FIFO_WDATA 0x88
> > +#define UART_FIFO_RDATA 0x8c
> > +#define UART_FIFO_RDATA_MSK GENMASK(7, 0)
> > +
> > +#define BFLB_UART_MAXPORTS 8
> > +#define BFLB_UART_BAUD 2000000
> > +#define BFLB_UART_RX_FIFO_TH 7
> > +#define BFLB_UART_TX_FIFO_TH 15
> > +#define BFLB_UART_URX_RTO_TIME 0x4f
> > +
> > +struct bflb_uart_port {
> > + struct uart_port port;
> > + struct clk *clk;
> > +};
> > +
> > +static struct bflb_uart_port *bflb_uart_ports[BFLB_UART_MAXPORTS];
> > +
> > +static inline u32 rdl(struct uart_port *port, u32 reg)
> > +{
> > + return readl_relaxed(port->membase + reg);
> > +}
> > +
> > +static inline void wrl(struct uart_port *port, u32 reg, u32 value)
> > +{
> > + writel_relaxed(value, port->membase + reg);
> > +}
> > +
> > +static inline void wrb(struct uart_port *port, u32 reg, u8 value)
> > +{
> > + writeb_relaxed(value, port->membase + reg);
> > +}
> > +
> > +static unsigned int bflb_uart_tx_empty(struct uart_port *port)
> > +{
> > + return (rdl(port, UART_FIFO_CONFIG_1) & UART_TX_FIFO_CNT_MSK) ? TIOCSER_TEMT : 0;
> > +}
> > +
> > +static unsigned int bflb_uart_get_mctrl(struct uart_port *port)
> > +{
> > + return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
> > +}
> > +
> > +static void bflb_uart_set_mctrl(struct uart_port *port, unsigned int sigs)
> > +{
> > +}
>
> Why is a blank function required here?
>
>
> > --- a/include/uapi/linux/serial_core.h
> > +++ b/include/uapi/linux/serial_core.h
> > @@ -279,4 +279,7 @@
> > /* Sunplus UART */
> > #define PORT_SUNPLUS 123
> >
> > +/* Bouffalolab UART */
> > +#define PORT_BFLB 124
>
> Why is this required? What userspace code is going to need this?
>
> thanks,
>
> greg k-h