Re: [PATCH v7 3/3] serial: sc16is7xx: add support for EXAR XR20M1172 UART

From: Konstantin P.
Date: Tue Apr 23 2024 - 13:30:09 EST

On Tue, Apr 23, 2024 at 8:28 PM Hugo Villeneuve <hugo@xxxxxxxxxxx> wrote:
>
> On Mon, 22 Apr 2024 16:32:15 +0300
> Konstantin Pugin <ria.freelander@xxxxxxxxx> wrote:
>
> Hi Konstantin,
>
> > XR20M1172 register set is mostly compatible with SC16IS762, but it has
> > a support for additional division rates of UART with special DLD register.
> > So, add handling this register by appropriate devicetree bindings.
> >
> > 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..09c9e52d7ec2 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 Register */
> >
> > /* 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);
> > }
> >
> > 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
>
> You are missing a semicolumn here, and compilation aborts. Looks like
> you didn't test.
>
> Hugo.
>
>
> > 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);
> > --
> > 2.34.1
> >
> >
> >
>
>
> --
> Hugo Villeneuve

WIll fix tomorrow (or today, if I will have time). Maybe I send not
latest version.