Support for Airoha AN7581 SoC UART and HSUART baud rate
calculation routine.
Signed-off-by: Benjamin Larsson <benjamin.larsson@xxxxxxxxxx>
---
drivers/tty/serial/8250/8250_airoha.c | 85 +++++++++++++++++++++++++++
drivers/tty/serial/8250/8250_of.c | 2 +
drivers/tty/serial/8250/8250_port.c | 26 ++++++++
drivers/tty/serial/8250/Kconfig | 10 ++++
drivers/tty/serial/8250/Makefile | 1 +
include/linux/serial_8250.h | 1 +
include/uapi/linux/serial_core.h | 6 ++
include/uapi/linux/serial_reg.h | 9 +++
8 files changed, 140 insertions(+)
create mode 100644 drivers/tty/serial/8250/8250_airoha.c
diff --git a/drivers/tty/serial/8250/8250_airoha.c b/drivers/tty/serial/8250/8250_airoha.c
new file mode 100644
index 000000000000..c57789dcc174
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_airoha.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Airoha UART driver.
+ *
+ * Copyright (c) 2025 Genexis Sweden AB
+ * Author: Benjamin Larsson <benjamin.larsson@xxxxxxxxxx>
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_reg.h>
+#include <linux/console.h>
+#include <linux/dma-mapping.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#include "8250.h"
+
+/* The Airoha UART is 16550-compatible except for the baud rate calculation.
+ *
+ * crystal_clock = 20 MHz
+ * xindiv_clock = crystal_clock / clock_div
+ * (x/y) = XYD, 32 bit register with 16 bits of x and then 16 bits of y
+ * clock_div = XINCLK_DIVCNT (default set to 10 (0x4)),
+ * - 3 bit register [ 1, 2, 4, 8, 10, 12, 16, 20 ]
+ *
+ * baud_rate = ((xindiv_clock) * (x/y)) / ([BRDH,BRDL] * 16)
+ *
+ * XYD_y seems to need to be larger then XYD_x for proper waveform generation.
+ * Setting [BRDH,BRDL] to [0,1] and XYD_y to 65000 give even values
+ * for usual baud rates.
+ *
+ * Selecting divider needs to fulfill
+ * 1.8432 MHz <= xindiv_clk <= APB clock / 2
+ * The clocks are unknown but a divider of value 1 did not result in a valid
+ * waveform.
+ *
+ */
+
+#define CLOCK_DIV_TAB_ELEMS 3
+#define XYD_Y 65000
+#define XINDIV_CLOCK 20000000
+#define UART_BRDL_20M 0x01
+#define UART_BRDH_20M 0x00
+static int clock_div_tab[] = { 10, 4, 2};
+static int clock_div_reg[] = { 4, 2, 1};
+
+int airoha8250_set_baud_rate(struct uart_port *port,
+ unsigned int baud, unsigned int hs)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
+ unsigned int xyd_x, nom, denom;
+
+ int i;
+ /* set DLAB to access the baud rate divider registers (BRDH, BRDL) */
+ serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
+ /* set baud rate calculation defaults */
+ /* set BRDIV ([BRDH,BRDL]) to 1 */
+ serial_port_out(port, UART_BRDL, UART_BRDL_20M);
+ serial_port_out(port, UART_BRDH, UART_BRDH_20M);
+ /* calculate XYD_x and XINCLKDR register
+ * for the HSUART xyd_x needs to be scale by a factor of 2
+ */
+ for (i = 0 ; i < CLOCK_DIV_TAB_ELEMS ; i++) {
+ denom = (XINDIV_CLOCK/40) / clock_div_tab[i];
+ nom = (baud * (XYD_Y/40));
+ xyd_x = ((nom/denom) << 4) >> hs;
+ if (xyd_x < XYD_Y)
+ break;
+ }
+ serial_port_out(port, UART_XINCLKDR, clock_div_reg[i]);
+ serial_port_out(port, UART_XYD, (xyd_x<<16) | XYD_Y);
+ /* unset DLAB */
+ serial_port_out(port, UART_LCR, up->lcr);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(airoha8250_set_baud_rate);
diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index 64aed7efc569..5315bc1bc06d 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -341,6 +341,8 @@ static const struct of_device_id of_platform_serial_table[] = {
{ .compatible = "ti,da830-uart", .data = (void *)PORT_DA830, },
{ .compatible = "nuvoton,wpcm450-uart", .data = (void *)PORT_NPCM, },
{ .compatible = "nuvoton,npcm750-uart", .data = (void *)PORT_NPCM, },
+ { .compatible = "airoha,airoha-uart", .data = (void *)PORT_AIROHA, },
+ { .compatible = "airoha,airoha-hsuart", .data = (void *)PORT_AIROHA_HS, },
{ /* end of list */ },
};
MODULE_DEVICE_TABLE(of, of_platform_serial_table);
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1ea52fce9bf1..00163a3d35cd 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -319,6 +319,22 @@ static const struct serial8250_config uart_config[] = {
.rxtrig_bytes = {1, 8, 16, 30},
.flags = UART_CAP_FIFO | UART_CAP_AFE,
},
+ [PORT_AIROHA] = {
+ .name = "Airoha UART",
+ .fifo_size = 8,
+ .tx_loadsz = 1,
+ .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_CLEAR_RCVR,
+ .rxtrig_bytes = {1, 4},
+ .flags = UART_CAP_FIFO,
+ },
+ [PORT_AIROHA_HS] = {
+ .name = "Airoha HSUART",
+ .fifo_size = 128,
+ .tx_loadsz = 128,
+ .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_CLEAR_RCVR,
+ .rxtrig_bytes = {1, 4},
+ .flags = UART_CAP_FIFO,
+ },
};
/* Uart divisor latch read */
@@ -2847,6 +2863,16 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
serial8250_set_divisor(port, baud, quot, frac);
+
+ /*
+ * Airoha SoCs have custom registers for baud rate settings
+ */
+#ifdef CONFIG_SERIAL_8250_AIROHA
+ if (port->type == PORT_AIROHA)
+ airoha8250_set_baud_rate(port, baud, 0);
+ if (port->type == PORT_AIROHA_HS)
+ airoha8250_set_baud_rate(port, baud, 1);
+#endif
/*
* LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
* is written without DLAB set, this mode will be disabled.
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 55d26d16df9b..97fe6ea9393d 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -356,6 +356,16 @@ config SERIAL_8250_ACORN
system, say Y to this option. The driver can handle 1, 2, or 3 port
cards. If unsure, say N.
+config SERIAL_8250_AIROHA
+ tristate "Airoha UART support"
+ depends on (ARCH_AIROHA || COMPILE_TEST) && OF && SERIAL_8250
+ help
+ Selecting this option enables an Airoha SoC specific baud rate
+ calculation routine on an otherwise 16550 compatible UART hardware.
+
+ If you have an Airoha based board and want to use the serial port,
+ say Y to this option. If unsure, say N.
+
config SERIAL_8250_BCM2835AUX
tristate "BCM2835 auxiliar mini UART support"
depends on ARCH_BCM2835 || COMPILE_TEST
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 1516de629b61..b7f07d5c4cca 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_SERIAL_8250_CONSOLE) += 8250_early.o
obj-$(CONFIG_SERIAL_8250_ACCENT) += 8250_accent.o
obj-$(CONFIG_SERIAL_8250_ACORN) += 8250_acorn.o
+obj-$(CONFIG_SERIAL_8250_AIROHA) += 8250_airoha.o
obj-$(CONFIG_SERIAL_8250_ASPEED_VUART) += 8250_aspeed_vuart.o
obj-$(CONFIG_SERIAL_8250_BCM2835AUX) += 8250_bcm2835aux.o
obj-$(CONFIG_SERIAL_8250_BCM7271) += 8250_bcm7271.o
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index e0717c8393d7..33e7e1922149 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -195,6 +195,7 @@ void serial8250_do_set_mctrl(struct uart_port *port, unsigned int mctrl);
void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
unsigned int quot);
int fsl8250_handle_irq(struct uart_port *port);
+int airoha8250_set_baud_rate(struct uart_port *port, unsigned int baud, unsigned int hs);
int serial8250_handle_irq(struct uart_port *port, unsigned int iir);
u16 serial8250_rx_chars(struct uart_8250_port *up, u16 lsr);
void serial8250_read_char(struct uart_8250_port *up, u16 lsr);
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index 9c007a106330..c71fb338accb 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -231,6 +231,12 @@
/* Sunplus UART */
#define PORT_SUNPLUS 123
+/* Airoha UART */
+#define PORT_AIROHA 124
+
+/* Airoha HSUART */
+#define PORT_AIROHA_HS 125
+
/* Generic type identifier for ports which type is not important to userspace. */
#define PORT_GENERIC (-1)
diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h
index 9c987b04e2d0..72a71e171602 100644
--- a/include/uapi/linux/serial_reg.h
+++ b/include/uapi/linux/serial_reg.h
@@ -383,5 +383,14 @@
#define UART_ALTR_EN_TXFIFO_LW 0x01 /* Enable the TX FIFO Low Watermark */
#define UART_ALTR_TX_LOW 0x41 /* Tx FIFO Low Watermark */
+/*
+ * These are definitions for the Airoha UART
+ * Normalized because of 32 bit registers.
+ */
+#define UART_BRDL 0
+#define UART_BRDH 1
+#define UART_XINCLKDR 10
+#define UART_XYD 11
+
#endif /* _LINUX_SERIAL_REG_H */
--
2.34.1
