From: Konstantin Pugin <ria.freelander@xxxxxxxxx>..
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.
Reviewed-by: Vladimir Zapolskiy <vz@xxxxxxxxx>
Signed-off-by: Konstantin Pugin <ria.freelander@xxxxxxxxx>
---
drivers/tty/serial/sc16is7xx.c | 55 +++++++++++++++++++++++++++++++---
1 file changed, 51 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index a300eebf1401..59376c637467 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -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 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(m) ((m) & GENMASK(3, 0))