From: Konstantin Pugin <[email protected]>
Its 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
via UPF_MAGIC_MULTIPLIER port flag.
Signed-off-by: Konstantin Pugin <[email protected]>
---
drivers/tty/serial/sc16is7xx.c | 54 ++++++++++++++++++++++++++++++++--
1 file changed, 51 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index a300eebf1401..7fc1c19b3891 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -65,6 +65,7 @@
/* 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 SC16IS7XX_DLD_REG (0x02) /* Divisor Latch Mode (only on EXAR chips) */
/* Enhanced Register set: Only if (LCR == 0xBF) */
#define SC16IS7XX_EFR_REG (0x02) /* Enhanced Features */
@@ -218,6 +219,20 @@
#define SC16IS7XX_TCR_RX_HALT(words) ((((words) / 4) & 0x0f) << 0)
#define SC16IS7XX_TCR_RX_RESUME(words) ((((words) / 4) & 0x0f) << 4)
+/* Divisor Latch Mode 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 SC16IS7XX_DLD_16X 0
+#define SC16IS7XX_DLD_DIV(m) ((m) & 0xf)
+#define SC16IS7XX_DLD_8X BIT(4)
+#define SC16IS7XX_DLD_4X BIT(5)
+
/*
* TLR register bits
* If TLR[3:0] or TLR[7:4] are logical 0, the selectable trigger levels via the
@@ -310,6 +325,7 @@ struct sc16is7xx_devtype {
char name[10];
int nr_gpio;
int nr_uart;
+ bool has_dld;
};
#define SC16IS7XX_RECONF_MD (1 << 0)
@@ -522,6 +538,13 @@ static const struct sc16is7xx_devtype sc16is762_devtype = {
.nr_uart = 2,
};
+static const struct sc16is7xx_devtype xr20m1172_devtype = {
+ .name = "XR20M1172",
+ .nr_gpio = 8,
+ .nr_uart = 2,
+ .has_dld = true,
+};
+
static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
{
switch (reg) {
@@ -559,13 +582,29 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
u8 lcr;
u8 prescaler = 0;
- unsigned long clk = port->uartclk, div = clk / 16 / baud;
+ u8 divisor = 16;
+ u8 dld_mode = SC16IS7XX_DLD_16X;
+ bool has_dld = !!(port->flags & UPF_MAGIC_MULTIPLIER);
+ unsigned long clk = port->uartclk, div, div16;
+
+ if (has_dld)
+ while (DIV_ROUND_CLOSEST(port->uartclk, baud) < divisor)
+ divisor /= 2;
+
+ div16 = clk * (16 / divisor) / baud;
+ div = div16 / 16; /* For divisor = 16, it is the same as clk / 16 / baud */
if (div >= BIT(16)) {
prescaler = SC16IS7XX_MCR_CLKSEL_BIT;
div /= 4;
}
+ /* Count additional divisor for EXAR devices */
+ if (divisor == 8)
+ dld_mode = SC16IS7XX_DLD_8X;
+ if (divisor == 4)
+ dld_mode = SC16IS7XX_DLD_4X;
+
/* Enable enhanced features */
sc16is7xx_efr_lock(port);
sc16is7xx_port_update(port, SC16IS7XX_EFR_REG,
@@ -586,12 +625,14 @@ 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, SC16IS7XX_DLD_REG, dld_mode | SC16IS7XX_DLD_DIV(div16));
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,
@@ -1014,6 +1055,7 @@ static void sc16is7xx_set_termios(struct uart_port *port,
unsigned int lcr, flow = 0;
int baud;
unsigned long flags;
+ bool has_dld = !!(port->flags & UPF_MAGIC_MULTIPLIER);
kthread_cancel_delayed_work_sync(&one->ms_work);
@@ -1093,7 +1135,7 @@ 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 / (has_dld ? 4 : 16));
/* Setup baudrate generator */
baud = sc16is7xx_set_baud(port, baud);
@@ -1550,6 +1592,9 @@ static int sc16is7xx_probe(struct device *dev,
s->p[i].port.type = PORT_SC16IS7XX;
s->p[i].port.fifosize = SC16IS7XX_FIFO_SIZE;
s->p[i].port.flags = UPF_FIXED_TYPE | UPF_LOW_LATENCY;
+ /* If we have DLD register, then set UPF_MAGIC_MULTIPLIER flag */
+ if (devtype->has_dld)
+ s->p[i].port.flags |= UPF_MAGIC_MULTIPLIER;
s->p[i].port.iobase = i;
/*
* Use all ones as membase to make sure uart_configure_port() in
@@ -1688,6 +1733,7 @@ static const struct of_device_id __maybe_unused sc16is7xx_dt_ids[] = {
{ .compatible = "nxp,sc16is752", .data = &sc16is752_devtype, },
{ .compatible = "nxp,sc16is760", .data = &sc16is760_devtype, },
{ .compatible = "nxp,sc16is762", .data = &sc16is762_devtype, },
+ { .compatible = "exar,xr20m1172", .data = &xr20m1172_devtype, },
{ }
};
MODULE_DEVICE_TABLE(of, sc16is7xx_dt_ids);
@@ -1776,6 +1822,7 @@ 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, },
{ }
};
@@ -1826,6 +1873,7 @@ 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);
--
2.34.1
On Thu, Apr 18, 2024 at 04:57:34PM +0300, Konstantin Pugin wrote:
> From: Konstantin Pugin <[email protected]>
>
> Its register set is mostly compatible with SC16IS762, but
"Its"? Whose? Elaborate, please.
> it has a support for additional division rates of UART
> with special DLD register. So, add handling this register
> via UPF_MAGIC_MULTIPLIER port flag.
Oh, can we avoid using this? You can redefine ->set_termios() if required and
before factor out the common pieces to the helper functions.
..
All three commit messages seems follow different text width, please keep it around
~60 for Subject and ~72 for the commit message.
..
> /* 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 SC16IS7XX_DLD_REG (0x02) /* Divisor Latch Mode (only on EXAR chips) */
Is it called DLD in the datasheet? If so, can you match the comment to
the datasheet, otherwise make it DLM and I would even go for the EXAR
namespace.
..
> +/* Divisor Latch Mode 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.
> + */
/*
* This is wrong multi-line comment
* style for this subsystem. Use this
* example.
*/
..
> +#define SC16IS7XX_DLD_16X 0
> +#define SC16IS7XX_DLD_DIV(m) ((m) & 0xf)
GENMASK() (since you already use BIT() below)
> +#define SC16IS7XX_DLD_8X BIT(4)
> +#define SC16IS7XX_DLD_4X BIT(5)
Perhaps also EXAR namespace.
..
> struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
> u8 lcr;
> u8 prescaler = 0;
> - unsigned long clk = port->uartclk, div = clk / 16 / baud;
> + u8 divisor = 16;
> + u8 dld_mode = SC16IS7XX_DLD_16X;
> + bool has_dld = !!(port->flags & UPF_MAGIC_MULTIPLIER);
> + unsigned long clk = port->uartclk, div, div16;
Please, try to keep it in reversed xmas tree order (longer lines first).
..
> + if (has_dld)
Can we actually replace this with some ID checks?
> + while (DIV_ROUND_CLOSEST(port->uartclk, baud) < divisor)
> + divisor /= 2;
Bit shifts and ffs() / fls() from bitops.h (or respective round*() / ilog2() /
etc. from log2.h) will help you to avoid while loop.
..
> + div16 = clk * (16 / divisor) / baud;
> + div = div16 / 16; /* For divisor = 16, it is the same as clk / 16 / baud */
So, these may loose in precision, right?
Wouldn't be better to have
div16 = (clk * 16) / divisor / baud;
div = div16 / 16;
?
> if (div >= BIT(16)) {
> prescaler = SC16IS7XX_MCR_CLKSEL_BIT;
> div /= 4;
> }
>
..
> { .compatible = "nxp,sc16is752", .data = &sc16is752_devtype, },
> { .compatible = "nxp,sc16is760", .data = &sc16is760_devtype, },
> { .compatible = "nxp,sc16is762", .data = &sc16is762_devtype, },
> + { .compatible = "exar,xr20m1172", .data = &xr20m1172_devtype, },
Sorted?
..
> + { "xr20m1172", (kernel_ulong_t)&xr20m1172_devtype, },
This gives a hint about the above mentioned EXAR namespace for the definitions,
i.e. use
#define XR20M1172_...
--
With Best Regards,
Andy Shevchenko