Re: [PATCH v9 3/3] serial: sc16is7xx: add support for EXAR XR20M1172 UART

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On Fri, Apr 26, 2024 at 12:19 AM Hugo Villeneuve <hugo@xxxxxxxxxxx> wrote:
>
> On Thu, 25 Apr 2024 21:32:35 +0300
> Konstantin Pugin <rilian.la.te@xxxxx> wrote:
>
> > From: Konstantin Pugin <ria.freelander@xxxxxxxxx>
> >
> > XR20M1172 register set is mostly compatible with SC16IS762, but it
> > supports for additional division rates with special DLD register.
> >
> > Reviewed-by: Andy Shevchenko <andy@xxxxxxxxxx>
> > Signed-off-by: Konstantin Pugin <ria.freelander@xxxxxxxxx>
> > ---
> >  drivers/tty/serial/Kconfig         |  3 +-
> >  drivers/tty/serial/sc16is7xx.c     | 61 ++++++++++++++++++++++++++++--
> >  drivers/tty/serial/sc16is7xx.h     |  1 +
> >  drivers/tty/serial/sc16is7xx_i2c.c |  1 +
> >  drivers/tty/serial/sc16is7xx_spi.c |  1 +
> >  5 files changed, 62 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> > index 4fdd7857ef4d..9d0438cfe147 100644
> > --- a/drivers/tty/serial/Kconfig
> > +++ b/drivers/tty/serial/Kconfig
> > @@ -1029,7 +1029,7 @@ config SERIAL_SC16IS7XX_CORE
> >       select SERIAL_SC16IS7XX_SPI if SPI_MASTER
> >       select SERIAL_SC16IS7XX_I2C if I2C
> >       help
> > -       Core driver for NXP SC16IS7xx UARTs.
> > +       Core driver for NXP SC16IS7xx and compatible UARTs.
> >         Supported ICs are:
> >
> >           SC16IS740
> > @@ -1038,6 +1038,7 @@ config SERIAL_SC16IS7XX_CORE
> >           SC16IS752
> >           SC16IS760
> >           SC16IS762
> > +         XR20M1172 (Exar)
> >
> >         The driver supports both I2C and SPI interfaces.
> >
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> > index dfcc804f558f..2b40600243a9 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -10,6 +10,7 @@
> >  #undef DEFAULT_SYMBOL_NAMESPACE
> >  #define DEFAULT_SYMBOL_NAMESPACE SERIAL_NXP_SC16IS7XX
> >
> > +#include <linux/bitfield.h>
> >  #include <linux/clk.h>
> >  #include <linux/delay.h>
> >  #include <linux/device.h>
> > @@ -68,6 +69,7 @@
> >  /* Special Register set: Only if ((LCR[7] == 1) && (LCR != 0xBF)) */
> >  #define SC16IS7XX_DLL_REG            (0x00) /* Divisor Latch Low */
> >  #define SC16IS7XX_DLH_REG            (0x01) /* Divisor Latch High */
> > +#define XR20M117X_DLD_REG            (0x02) /* Divisor Fractional (requires EFR[4] = 1) */
> >
> >  /* Enhanced Register set: Only if (LCR == 0xBF) */
> >  #define SC16IS7XX_EFR_REG            (0x02) /* Enhanced Features */
> > @@ -221,6 +223,20 @@
> >  #define SC16IS7XX_TCR_RX_HALT(words) ((((words) / 4) & 0x0f) << 0)
> >  #define SC16IS7XX_TCR_RX_RESUME(words)       ((((words) / 4) & 0x0f) << 4)
> >
> > +/*
> > + * Divisor Fractional Register bits (EXAR extension).
> > + * EXAR hardware is mostly compatible with SC16IS7XX, but supports additional feature:
> > + * 4x and 8x divisor, instead of default 16x. It has a special register to program it.
> > + * Bits 0 to 3 is fractional divisor, it used to set value of last 16 bits of
> > + * uartclk * (16 / divisor) / baud, in case of default it will be uartclk / baud.
> > + * Bits 4 and 5 used as switches, and should not be set to 1 simultaneously.
> > + */
> > +
> > +#define XR20M117X_DLD_16X                    0
> > +#define XR20M117X_DLD_DIV_MASK                       GENMASK(3, 0)
> > +#define XR20M117X_DLD_8X                     BIT(4)
> > +#define XR20M117X_DLD_4X                     BIT(5)
> > +
> >  /*
> >   * TLR register bits
> >   * If TLR[3:0] or TLR[7:4] are logical 0, the selectable trigger levels via the
> > @@ -523,6 +539,13 @@ const struct sc16is7xx_devtype sc16is762_devtype = {
> >  };
> >  EXPORT_SYMBOL_GPL(sc16is762_devtype);
> >
> > +const struct sc16is7xx_devtype xr20m1172_devtype = {
> > +     .name           = "XR20M1172",
> > +     .nr_gpio        = 8,
> > +     .nr_uart        = 2,
> > +};
> > +EXPORT_SYMBOL_GPL(xr20m1172_devtype);
> > +
> >  static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
> >  {
> >       switch (reg) {
> > @@ -555,18 +578,43 @@ static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg)
> >       return reg == SC16IS7XX_RHR_REG;
> >  }
> >
> > +static bool sc16is7xx_has_dld(struct device *dev)
> > +{
> > +     struct sc16is7xx_port *s = dev_get_drvdata(dev);
> > +
> > +     if (s->devtype == &xr20m1172_devtype)
> > +             return true;
> > +     return false;
> > +}
> > +
> >  static int sc16is7xx_set_baud(struct uart_port *port, int baud)
> >  {
> >       struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> > -     u8 lcr;
> > +     unsigned long clk = port->uartclk, div, div16;
> > +     bool has_dld = sc16is7xx_has_dld(port->dev);
> > +     u8 dld_mode = XR20M117X_DLD_16X;
> >       u8 prescaler = 0;
> > -     unsigned long clk = port->uartclk, div = clk / 16 / baud;
> > +     u8 divisor = 16;
> > +     u8 lcr;
> > +
> > +     if (has_dld && DIV_ROUND_CLOSEST(clk, baud) < 16)
> > +             divisor = rounddown_pow_of_two(DIV_ROUND_CLOSEST(clk, baud));
> > +
> > +     div16 = (clk * 16) / divisor / baud;
> > +     div = div16 / 16;
> >
> >       if (div >= BIT(16)) {
> >               prescaler = SC16IS7XX_MCR_CLKSEL_BIT;
> >               div /= 4;
> >       }
> >
> > +     /* Count additional divisor for EXAR devices */
> > +     if (divisor == 8)
> > +             dld_mode = XR20M117X_DLD_8X;
> > +     if (divisor == 4)
> > +             dld_mode = XR20M117X_DLD_4X;
> > +     dld_mode |= FIELD_PREP(XR20M117X_DLD_DIV_MASK, div16);
> > +
> >       /* Enable enhanced features */
> >       sc16is7xx_efr_lock(port);
> >       sc16is7xx_port_update(port, SC16IS7XX_EFR_REG,
> > @@ -587,12 +635,14 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
> >       regcache_cache_bypass(one->regmap, true);
> >       sc16is7xx_port_write(port, SC16IS7XX_DLH_REG, div / 256);
> >       sc16is7xx_port_write(port, SC16IS7XX_DLL_REG, div % 256);
> > +     if (has_dld)
> > +             sc16is7xx_port_write(port, XR20M117X_DLD_REG, dld_mode);
> >       regcache_cache_bypass(one->regmap, false);
> >
> >       /* Restore LCR and access to general register set */
> >       sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
> >
> > -     return DIV_ROUND_CLOSEST(clk / 16, div);
> > +     return DIV_ROUND_CLOSEST(clk / divisor, div);
>
> While trying to review your code, it made me realize there is a bug
> with the current return value. I will send a patch to fix it, and you
> will be able to rebase your patchset on it after that.

It is good. What bug are you observed?

> Hugo.
>
>
> >  }
> >
> >  static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
> > @@ -1002,6 +1052,8 @@ static void sc16is7xx_set_termios(struct uart_port *port,
> >                                 const struct ktermios *old)
> >  {
> >       struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> > +     bool has_dld = sc16is7xx_has_dld(port->dev);
> > +     u8 divisor = has_dld ? 4 : 16;
> >       unsigned int lcr, flow = 0;
> >       int baud;
> >       unsigned long flags;
> > @@ -1084,7 +1136,7 @@ static void sc16is7xx_set_termios(struct uart_port *port,
> >       /* Get baud rate generator configuration */
> >       baud = uart_get_baud_rate(port, termios, old,
> >                                 port->uartclk / 16 / 4 / 0xffff,
> > -                               port->uartclk / 16);
> > +                               port->uartclk / divisor);
> >
> >       /* Setup baudrate generator */
> >       baud = sc16is7xx_set_baud(port, baud);
> > @@ -1684,6 +1736,7 @@ void sc16is7xx_remove(struct device *dev)
> >  EXPORT_SYMBOL_GPL(sc16is7xx_remove);
> >
> >  const struct of_device_id __maybe_unused sc16is7xx_dt_ids[] = {
> > +     { .compatible = "exar,xr20m1172",       .data = &xr20m1172_devtype, },
> >       { .compatible = "nxp,sc16is740",        .data = &sc16is74x_devtype, },
> >       { .compatible = "nxp,sc16is741",        .data = &sc16is74x_devtype, },
> >       { .compatible = "nxp,sc16is750",        .data = &sc16is750_devtype, },
> > diff --git a/drivers/tty/serial/sc16is7xx.h b/drivers/tty/serial/sc16is7xx.h
> > index afb784eaee45..eb2e3bc86f15 100644
> > --- a/drivers/tty/serial/sc16is7xx.h
> > +++ b/drivers/tty/serial/sc16is7xx.h
> > @@ -28,6 +28,7 @@ extern const struct sc16is7xx_devtype sc16is750_devtype;
> >  extern const struct sc16is7xx_devtype sc16is752_devtype;
> >  extern const struct sc16is7xx_devtype sc16is760_devtype;
> >  extern const struct sc16is7xx_devtype sc16is762_devtype;
> > +extern const struct sc16is7xx_devtype xr20m1172_devtype;
> >
> >  const char *sc16is7xx_regmap_name(u8 port_id);
> >
> > diff --git a/drivers/tty/serial/sc16is7xx_i2c.c b/drivers/tty/serial/sc16is7xx_i2c.c
> > index 3ed47c306d85..839de902821b 100644
> > --- a/drivers/tty/serial/sc16is7xx_i2c.c
> > +++ b/drivers/tty/serial/sc16is7xx_i2c.c
> > @@ -46,6 +46,7 @@ static const struct i2c_device_id sc16is7xx_i2c_id_table[] = {
> >       { "sc16is752",  (kernel_ulong_t)&sc16is752_devtype, },
> >       { "sc16is760",  (kernel_ulong_t)&sc16is760_devtype, },
> >       { "sc16is762",  (kernel_ulong_t)&sc16is762_devtype, },
> > +     { "xr20m1172",  (kernel_ulong_t)&xr20m1172_devtype, },
> >       { }
> >  };
> >  MODULE_DEVICE_TABLE(i2c, sc16is7xx_i2c_id_table);
> > diff --git a/drivers/tty/serial/sc16is7xx_spi.c b/drivers/tty/serial/sc16is7xx_spi.c
> > index 73df36f8a7fd..2b278282dbd0 100644
> > --- a/drivers/tty/serial/sc16is7xx_spi.c
> > +++ b/drivers/tty/serial/sc16is7xx_spi.c
> > @@ -69,6 +69,7 @@ static const struct spi_device_id sc16is7xx_spi_id_table[] = {
> >       { "sc16is752",  (kernel_ulong_t)&sc16is752_devtype, },
> >       { "sc16is760",  (kernel_ulong_t)&sc16is760_devtype, },
> >       { "sc16is762",  (kernel_ulong_t)&sc16is762_devtype, },
> > +     { "xr20m1172",  (kernel_ulong_t)&xr20m1172_devtype, },
> >       { }
> >  };
> >  MODULE_DEVICE_TABLE(spi, sc16is7xx_spi_id_table);
> > --
> > 2.44.0
> >
> >
> >
>
>
> --
> Hugo Villeneuve





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