[PATCH v4] lib: utils: serial: Add Cadence UART driver

Anup Patel anup at brainfault.org
Sun Aug 21 20:08:40 PDT 2022


On Wed, Aug 17, 2022 at 9:11 PM Jun Liang Tan
<junliang.tan at linux.starfivetech.com> wrote:
>
> Add Cadence UART driver
>
> Signed-off-by: Jun Liang Tan <junliang.tan at linux.starfivetech.com>
> Signed-off-by: Wei Liang Lim <weiliang.lim at linux.starfivetech.com>

Overall, this looks good except the divide-by-zero question raised by
other folks in uart_min_clk_divisor().

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>
> Changes in v4:
> - Add changelog
> - Check for possible divide-by-zero in uart_min_clk_divisor() by
>   referring to the fix in commit f27203525aa2fc20d0074feb892a6f8433f84e3a
> - Cosmetic changes
>
> Changes in v3:
> - Place #define register name in ascending order of register offset
> - Change #define register name to match manual register name
> - #define register flags in a way associate with their register
> - Cosmetic changes
>
> Changes in v2:
> - Rename fdt_parse_uart8250_node() to fdt_parse_uart_node() and make
>   neccessary changes in functions that call it
> - Align patch with the latest OpenSBI sources
>
>  include/sbi_utils/fdt/fdt_helper.h      |   4 +-
>  include/sbi_utils/serial/cadence-uart.h |  16 +++
>  lib/utils/fdt/fdt_helper.c              |   6 +-
>  lib/utils/serial/Kconfig                |   9 ++
>  lib/utils/serial/cadence-uart.c         | 128 ++++++++++++++++++++++++
>  lib/utils/serial/fdt_serial_cadence.c   |  35 +++++++
>  lib/utils/serial/fdt_serial_uart8250.c  |   2 +-
>  lib/utils/serial/objects.mk             |   4 +
>  platform/generic/configs/defconfig      |   1 +
>  9 files changed, 199 insertions(+), 6 deletions(-)
>  create mode 100644 include/sbi_utils/serial/cadence-uart.h
>  create mode 100644 lib/utils/serial/cadence-uart.c
>  create mode 100644 lib/utils/serial/fdt_serial_cadence.c
>
> diff --git a/include/sbi_utils/fdt/fdt_helper.h b/include/sbi_utils/fdt/fdt_helper.h
> index c60af35..bcd4996 100644
> --- a/include/sbi_utils/fdt/fdt_helper.h
> +++ b/include/sbi_utils/fdt/fdt_helper.h
> @@ -65,8 +65,8 @@ int fdt_parse_shakti_uart_node(void *fdt, int nodeoffset,
>  int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
>                                struct platform_uart_data *uart);
>
> -int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
> -                           struct platform_uart_data *uart);
> +int fdt_parse_uart_node(void *fdt, int nodeoffset,
> +                       struct platform_uart_data *uart);
>
>  int fdt_parse_uart8250(void *fdt, struct platform_uart_data *uart,
>                        const char *compatible);
> diff --git a/include/sbi_utils/serial/cadence-uart.h b/include/sbi_utils/serial/cadence-uart.h
> new file mode 100644
> index 0000000..e75fb95
> --- /dev/null
> +++ b/include/sbi_utils/serial/cadence-uart.h
> @@ -0,0 +1,16 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 StarFive Technology Co., Ltd.
> + *
> + * Author: Jun Liang Tan <junliang.tan at linux.starfivetech.com>
> + */
> +
> +#ifndef __SERIAL_CADENCE_UART_H__
> +#define __SERIAL_CADENCE_UART_H__
> +
> +#include <sbi/sbi_types.h>
> +
> +int cadence_uart_init(unsigned long base, u32 in_freq, u32 baudrate);
> +
> +#endif
> diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
> index c6abf80..6a75d6f 100644
> --- a/lib/utils/fdt/fdt_helper.c
> +++ b/lib/utils/fdt/fdt_helper.c
> @@ -401,8 +401,8 @@ int fdt_parse_sifive_uart_node(void *fdt, int nodeoffset,
>         return 0;
>  }
>
> -int fdt_parse_uart8250_node(void *fdt, int nodeoffset,
> -                           struct platform_uart_data *uart)
> +int fdt_parse_uart_node(void *fdt, int nodeoffset,
> +                       struct platform_uart_data *uart)
>  {
>         int len, rc;
>         const fdt32_t *val;
> @@ -447,7 +447,7 @@ int fdt_parse_uart8250(void *fdt, struct platform_uart_data *uart,
>         if (nodeoffset < 0)
>                 return nodeoffset;
>
> -       return fdt_parse_uart8250_node(fdt, nodeoffset, uart);
> +       return fdt_parse_uart_node(fdt, nodeoffset, uart);
>  }
>
>  int fdt_parse_xlnx_uartlite_node(void *fdt, int nodeoffset,
> diff --git a/lib/utils/serial/Kconfig b/lib/utils/serial/Kconfig
> index 152060d..6e425f2 100644
> --- a/lib/utils/serial/Kconfig
> +++ b/lib/utils/serial/Kconfig
> @@ -9,6 +9,11 @@ config FDT_SERIAL
>
>  if FDT_SERIAL
>
> +config FDT_SERIAL_CADENCE
> +       bool "Cadence UART FDT driver"
> +       select SERIAL_CADENCE
> +       default n
> +
>  config FDT_SERIAL_GAISLER
>         bool "Gaisler UART FDT driver"
>         select SERIAL_GAISLER
> @@ -46,6 +51,10 @@ config FDT_SERIAL_XILINX_UARTLITE
>
>  endif
>
> +config SERIAL_CADENCE
> +       bool "Cadence UART support"
> +       default n
> +
>  config SERIAL_GAISLER
>         bool "Gaisler UART support"
>         default n
> diff --git a/lib/utils/serial/cadence-uart.c b/lib/utils/serial/cadence-uart.c
> new file mode 100644
> index 0000000..8a2b6ba
> --- /dev/null
> +++ b/lib/utils/serial/cadence-uart.c
> @@ -0,0 +1,128 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 StarFive Technology Co., Ltd.
> + *
> + * Author: Jun Liang Tan <junliang.tan at linux.starfivetech.com>
> + */
> +
> +#include <sbi/riscv_io.h>
> +#include <sbi/sbi_console.h>
> +#include <sbi_utils/serial/cadence-uart.h>
> +
> +/* clang-format off */
> +
> +#define UART_REG_CTRL          0x00
> +#define UART_REG_MODE          0x04
> +#define UART_REG_IDR           0x0C
> +#define UART_REG_BRGR          0x18
> +#define UART_REG_CSR           0x2C
> +#define UART_REG_RFIFO_TFIFO   0x30
> +#define UART_REG_BDIVR         0x34
> +
> +#define UART_CTRL_RXRES                0x00000001
> +#define UART_CTRL_TXRES                0x00000002
> +#define UART_CTRL_RXEN         0x00000004
> +#define UART_CTRL_RXDIS                0x00000008
> +#define UART_CTRL_TXEN         0x00000010
> +#define UART_CTRL_TXDIS                0x00000020
> +
> +#define UART_MODE_PAR_NONE     0x00000020      /* No parity set */
> +
> +#define UART_BRGR_CD_CLKDIVISOR        0x00000001      /* baud_sample = sel_clk */
> +
> +#define        UART_CSR_REMPTY         0x00000002
> +#define        UART_CSR_TFUL           0x00000010
> +
> +/* clang-format on */
> +
> +static volatile void *uart_base;
> +static u32 uart_in_freq;
> +static u32 uart_baudrate;
> +
> +/*
> + * Find minimum divisor divides in_freq to max_target_hz;
> + * Based on SiFive UART driver (sifive-uart.c)
> + */
> +static inline unsigned int uart_min_clk_divisor(uint64_t in_freq,
> +                                               uint64_t max_target_hz)
> +{
> +       uint64_t quotient = (in_freq + max_target_hz - 1) / (max_target_hz);
> +
> +       /* Avoid underflow */
> +       if (quotient == 0)
> +               return 0;
> +       else
> +               return quotient - 1;
> +}
> +
> +static u32 get_reg(u32 offset)
> +{
> +       return readl(uart_base + offset);
> +}
> +
> +static void set_reg(u32 offset, u32 val)
> +{
> +       writel(val, uart_base + offset);
> +}
> +
> +static void cadence_uart_putc(char ch)
> +{
> +       while (get_reg(UART_REG_CSR) & UART_CSR_TFUL)
> +               ;
> +
> +       set_reg(UART_REG_RFIFO_TFIFO, ch);
> +}
> +
> +static int cadence_uart_getc(void)
> +{
> +       u32 ret = get_reg(UART_REG_CSR);
> +
> +       if (!(ret & UART_CSR_REMPTY))
> +               return get_reg(UART_REG_RFIFO_TFIFO);
> +
> +       return -1;
> +}
> +
> +static struct sbi_console_device cadence_console = {
> +       .name = "cadence_uart",
> +       .console_putc = cadence_uart_putc,
> +       .console_getc = cadence_uart_getc
> +};
> +
> +int cadence_uart_init(unsigned long base, u32 in_freq, u32 baudrate)
> +{
> +       uart_base     = (volatile void *)base;
> +       uart_in_freq  = in_freq;
> +       uart_baudrate = baudrate;
> +
> +       /* Disable interrupts */
> +       set_reg(UART_REG_IDR, 0xFFFFFFFF);
> +
> +       /* Disable TX RX */
> +       set_reg(UART_REG_CTRL, UART_CTRL_TXDIS | UART_CTRL_RXDIS);
> +
> +       /* Configure baudrate */
> +       if (in_freq && baudrate) {
> +               set_reg(UART_REG_BRGR, UART_BRGR_CD_CLKDIVISOR);
> +               set_reg(UART_REG_BDIVR,
> +                       uart_min_clk_divisor(in_freq, baudrate));
> +       }
> +
> +       /* Software reset TX RX data path and enable TX RX */
> +       set_reg(UART_REG_CTRL, UART_CTRL_TXRES | UART_CTRL_RXRES
> +               | UART_CTRL_TXEN | UART_CTRL_RXEN);
> +
> +       /*
> +        * Set:
> +        * 1 stop bit, bits[07:06] = 0x00,
> +        * no parity set, bits[05:03] = 0x100,
> +        * 8 bits character length, bits[02:01] = 0x00,
> +        * sel_clk = uart_clk, bit[0] = 0x0
> +        */
> +       set_reg(UART_REG_MODE, UART_MODE_PAR_NONE);
> +
> +       sbi_console_set_device(&cadence_console);
> +
> +       return 0;
> +}
> diff --git a/lib/utils/serial/fdt_serial_cadence.c b/lib/utils/serial/fdt_serial_cadence.c
> new file mode 100644
> index 0000000..946e533
> --- /dev/null
> +++ b/lib/utils/serial/fdt_serial_cadence.c
> @@ -0,0 +1,35 @@
> +/*
> + * SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (c) 2022 StarFive Technology Co., Ltd.
> + *
> + * Author: Jun Liang Tan <junliang.tan at linux.starfivetech.com>
> + */
> +
> +#include <sbi_utils/fdt/fdt_helper.h>
> +#include <sbi_utils/serial/fdt_serial.h>
> +#include <sbi_utils/serial/cadence-uart.h>
> +
> +static int serial_cadence_init(void *fdt, int nodeoff,
> +                              const struct fdt_match *match)
> +{
> +       int rc;
> +       struct platform_uart_data uart = { 0 };
> +
> +       rc = fdt_parse_uart_node(fdt, nodeoff, &uart);
> +       if (rc)
> +               return rc;
> +
> +       return cadence_uart_init(uart.addr, uart.freq, uart.baud);
> +}
> +
> +static const struct fdt_match serial_cadence_match[] = {
> +       { .compatible = "cdns,uart-r1p12" },
> +       { .compatible = "starfive,jh8100-uart" },
> +       { },
> +};
> +
> +struct fdt_serial fdt_serial_cadence = {
> +       .match_table = serial_cadence_match,
> +       .init = serial_cadence_init
> +};
> diff --git a/lib/utils/serial/fdt_serial_uart8250.c b/lib/utils/serial/fdt_serial_uart8250.c
> index 0b95f2d..7b5d6a4 100644
> --- a/lib/utils/serial/fdt_serial_uart8250.c
> +++ b/lib/utils/serial/fdt_serial_uart8250.c
> @@ -17,7 +17,7 @@ static int serial_uart8250_init(void *fdt, int nodeoff,
>         int rc;
>         struct platform_uart_data uart = { 0 };
>
> -       rc = fdt_parse_uart8250_node(fdt, nodeoff, &uart);
> +       rc = fdt_parse_uart_node(fdt, nodeoff, &uart);
>         if (rc)
>                 return rc;
>
> diff --git a/lib/utils/serial/objects.mk b/lib/utils/serial/objects.mk
> index fa9f5a3..efb1d9e 100644
> --- a/lib/utils/serial/objects.mk
> +++ b/lib/utils/serial/objects.mk
> @@ -10,6 +10,9 @@
>  libsbiutils-objs-$(CONFIG_FDT_SERIAL) += serial/fdt_serial.o
>  libsbiutils-objs-$(CONFIG_FDT_SERIAL) += serial/fdt_serial_drivers.o
>
> +carray-fdt_serial_drivers-$(CONFIG_FDT_SERIAL_CADENCE) += fdt_serial_cadence
> +libsbiutils-objs-$(CONFIG_FDT_SERIAL_CADENCE) += serial/fdt_serial_cadence.o
> +
>  carray-fdt_serial_drivers-$(CONFIG_FDT_SERIAL_GAISLER) += fdt_serial_gaisler
>  libsbiutils-objs-$(CONFIG_FDT_SERIAL_GAISLER) += serial/fdt_serial_gaisler.o
>
> @@ -31,6 +34,7 @@ libsbiutils-objs-$(CONFIG_FDT_SERIAL_UART8250) += serial/fdt_serial_uart8250.o
>  carray-fdt_serial_drivers-$(CONFIG_FDT_SERIAL_XILINX_UARTLITE) += fdt_serial_xlnx_uartlite
>  libsbiutils-objs-$(CONFIG_FDT_SERIAL_XILINX_UARTLITE) += serial/fdt_serial_xlnx_uartlite.o
>
> +libsbiutils-objs-$(CONFIG_SERIAL_CADENCE) += serial/cadence-uart.o
>  libsbiutils-objs-$(CONFIG_SERIAL_GAISLER) += serial/gaisler-uart.o
>  libsbiutils-objs-$(CONFIG_SERIAL_SHAKTI) += serial/shakti-uart.o
>  libsbiutils-objs-$(CONFIG_SERIAL_SIFIVE) += serial/sifive-uart.o
> diff --git a/platform/generic/configs/defconfig b/platform/generic/configs/defconfig
> index 2a75394..e324173 100644
> --- a/platform/generic/configs/defconfig
> +++ b/platform/generic/configs/defconfig
> @@ -18,6 +18,7 @@ CONFIG_FDT_RESET_SIFIVE_TEST=y
>  CONFIG_FDT_RESET_SUNXI_WDT=y
>  CONFIG_FDT_RESET_THEAD=y
>  CONFIG_FDT_SERIAL=y
> +CONFIG_FDT_SERIAL_CADENCE=y
>  CONFIG_FDT_SERIAL_GAISLER=y
>  CONFIG_FDT_SERIAL_HTIF=y
>  CONFIG_FDT_SERIAL_SHAKTI=y
> --
> 2.37.1
>
>
>
> --
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