* [PATCH v2 1/2] dt-bindings: serial: 8250: Add Airoha compatibles
2026-07-24 18:30 [PATCH v2 0/2] serial: 8250: Add AN7581 UART support Christian Marangi
@ 2026-07-24 18:30 ` Christian Marangi
2026-07-24 18:30 ` [PATCH v2 2/2] serial: 8250: Add Airoha SoC UART and HSUART support Christian Marangi
1 sibling, 0 replies; 4+ messages in thread
From: Christian Marangi @ 2026-07-24 18:30 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby, Rob Herring, Krzysztof Kozlowski,
Conor Dooley, Ilpo Järvinen, Andy Shevchenko,
Benjamin Larsson, Christian Marangi, John Ogness, Peng Zhang,
Jacques Nilo, Rong Zhang, Gerhard Engleder, Jiaxun Yang,
Randy Dunlap, Binbin Zhou, Lubomir Rintel, devicetree,
linux-kernel, linux-serial
Cc: Conor Dooley
From: Benjamin Larsson <benjamin.larsson@genexis.eu>
The Airoha SoC family have a mostly 16550-compatible UART
and High-Speed UART hardware with the exception of custom
baud rate settings register.
Signed-off-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
---
Documentation/devicetree/bindings/serial/8250.yaml | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
index bb7b9c87a807..b6f7e093d8d7 100644
--- a/Documentation/devicetree/bindings/serial/8250.yaml
+++ b/Documentation/devicetree/bindings/serial/8250.yaml
@@ -110,6 +110,11 @@ properties:
- const: mrvl,pxa-uart
- const: nuvoton,wpcm450-uart
- const: nuvoton,npcm750-uart
+ - const: airoha,en7523-uart
+ - items:
+ - const: airoha,an7581-uart
+ - const: airoha,en7523-uart
+ - const: airoha,an7581-hsuart
- const: nvidia,tegra20-uart
- const: nxp,lpc3220-uart
- items:
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v2 2/2] serial: 8250: Add Airoha SoC UART and HSUART support
2026-07-24 18:30 [PATCH v2 0/2] serial: 8250: Add AN7581 UART support Christian Marangi
2026-07-24 18:30 ` [PATCH v2 1/2] dt-bindings: serial: 8250: Add Airoha compatibles Christian Marangi
@ 2026-07-24 18:30 ` Christian Marangi
2026-07-24 18:43 ` sashiko-bot
1 sibling, 1 reply; 4+ messages in thread
From: Christian Marangi @ 2026-07-24 18:30 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby, Rob Herring, Krzysztof Kozlowski,
Conor Dooley, Ilpo Järvinen, Andy Shevchenko,
Benjamin Larsson, Christian Marangi, John Ogness, Peng Zhang,
Jacques Nilo, Rong Zhang, Gerhard Engleder, Jiaxun Yang,
Randy Dunlap, Binbin Zhou, Lubomir Rintel, devicetree,
linux-kernel, linux-serial
Add support for Airoha AN7523 UART and AN7581 HSUART.
These implement a standard 16550 UART with only some custom logic
for baud rate handling.
Co-developed-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Signed-off-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
drivers/tty/serial/8250/8250.h | 6 +
drivers/tty/serial/8250/8250_airoha.c | 190 ++++++++++++++++++++++++++
drivers/tty/serial/8250/8250_port.c | 16 +++
drivers/tty/serial/8250/Kconfig | 11 ++
drivers/tty/serial/8250/Makefile | 1 +
5 files changed, 224 insertions(+)
create mode 100644 drivers/tty/serial/8250/8250_airoha.c
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 77fe0588fd6b..e6b2b9431229 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -73,6 +73,12 @@ struct serial8250_config {
unsigned int flags;
};
+enum uart_port_type {
+ /* Internal 8250 only */
+ UART_PORT_AIROHA = 124,
+ UART_PORT_AIROHA_HS = 125,
+};
+
#define UART_CAP_FIFO BIT(8) /* UART has FIFO */
#define UART_CAP_EFR BIT(9) /* UART has EFR */
#define UART_CAP_SLEEP BIT(10) /* UART has IER sleep */
diff --git a/drivers/tty/serial/8250/8250_airoha.c b/drivers/tty/serial/8250/8250_airoha.c
new file mode 100644
index 000000000000..5d6d998bebd6
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_airoha.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Airoha UART driver
+ *
+ * Copyright (c) 2025 Genexis Sweden AB
+ * Author: Benjamin Larsson <benjamin.larsson@genexis.eu>
+ * Christian Marangi <ansuelsmth@gmail.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/math64.h>
+#include <linux/property.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+
+#include "8250.h"
+
+#define UART_AIROHA_BRDL 0
+#define UART_AIROHA_BRDH 1
+#define UART_AIROHA_XINCLKDR 10
+#define UART_AIROHA_XYD 11
+#define UART_AIROHA_XYD_X GENMASK(31, 16)
+#define UART_AIROHA_XYD_Y GENMASK(15, 0)
+
+struct airoha_8250_priv {
+ int line;
+};
+
+struct airoha_8250_clk_div_info {
+ unsigned int div;
+ u32 mask;
+};
+
+#define UART_BRDL_20M 0x01
+#define UART_BRDH_20M 0x00
+
+#define XINDIV_CLOCK 20000000
+#define XYD_Y 65000
+
+static const struct airoha_8250_clk_div_info airoha_clk_div_info[] = {
+ { .div = 10, .mask = BIT(2) },
+ { .div = 4, .mask = BIT(1) },
+ { .div = 2, .mask = BIT(0) },
+};
+
+static unsigned int airoha_get_divisor(struct uart_port *port,
+ unsigned int baud,
+ unsigned int *frac)
+{
+ /* Hardware always uses BRDIV = 1. */
+ *frac = 0;
+
+ return 1;
+}
+
+/*
+ * Airoha UART baud rate calculation logic
+ *
+ * crystal_clock = 20 MHz (fixed frequency)
+ * 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)
+ *
+ * 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.
+ *
+ * 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 gives even values
+ * for usual baud rates.
+ */
+static void airoha_set_divisor(struct uart_port *port, unsigned int baud,
+ unsigned int quot, unsigned int quot_frac)
+{
+ const struct airoha_8250_clk_div_info *clk_div_info;
+ struct uart_8250_port *up = up_to_u8250p(port);
+ u32 xindiv_clk;
+ u64 xyd_x, nom;
+ 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 (BRDIV ([BRDH,BRDL]) to 1) */
+ serial_port_out(port, UART_AIROHA_BRDL, UART_BRDL_20M);
+ serial_port_out(port, UART_AIROHA_BRDH, UART_BRDH_20M);
+
+ /*
+ * Calculate XYD_x and XINCLKDR register by searching
+ * through a table of crystal_clock divisors.
+ */
+ nom = baud * XYD_Y;
+ for (i = 0 ; i < ARRAY_SIZE(airoha_clk_div_info) ; i++) {
+ clk_div_info = &airoha_clk_div_info[i];
+
+ xindiv_clk = XINDIV_CLOCK / clk_div_info->div;
+ xyd_x = div_u64(nom, xindiv_clk) * 16;
+
+ /* For the HSUART xyd_x needs to be scaled by a factor of 2 */
+ if (port->type == UART_PORT_AIROHA_HS)
+ xyd_x /= 2;
+
+ if (xyd_x < XYD_Y)
+ break;
+ }
+
+ serial_port_out(port, UART_AIROHA_XINCLKDR, clk_div_info->mask);
+ serial_port_out(port, UART_AIROHA_XYD,
+ FIELD_PREP(UART_AIROHA_XYD_X, xyd_x) |
+ FIELD_PREP(UART_AIROHA_XYD_Y, XYD_Y));
+
+ /* Restore normal register access. */
+ serial_port_out(port, UART_LCR, up->lcr);
+}
+
+static int airoha_8250_probe(struct platform_device *pdev)
+{
+ struct uart_8250_port uart = { };
+ struct device *dev = &pdev->dev;
+ struct airoha_8250_priv *priv;
+ struct resource *res;
+ int ret;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res)
+ return dev_err_probe(dev, -EINVAL, "invalid address\n");
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ uart.port.dev = dev;
+ if (device_is_compatible(dev, "airoha,an7581-hsuart"))
+ uart.port.type = UART_PORT_AIROHA_HS;
+ else
+ uart.port.type = UART_PORT_AIROHA;
+ uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT |
+ UPF_FIXED_TYPE | UPF_IOREMAP;
+ uart.port.set_divisor = airoha_set_divisor;
+ uart.port.get_divisor = airoha_get_divisor;
+ uart.port.mapbase = res->start;
+ uart.port.mapsize = resource_size(res);
+
+ ret = uart_read_and_validate_port_properties(&uart.port);
+ if (ret)
+ return ret;
+
+ ret = serial8250_register_8250_port(&uart);
+ if (ret < 0)
+ return ret;
+
+ priv->line = ret;
+ platform_set_drvdata(pdev, priv);
+
+ return 0;
+}
+
+static void airoha_8250_remove(struct platform_device *ofdev)
+{
+ struct airoha_8250_priv *priv = platform_get_drvdata(ofdev);
+
+ serial8250_unregister_port(priv->line);
+}
+
+static const struct of_device_id airoha_8250_dt_ids[] = {
+ { .compatible = "airoha,en7523-uart" },
+ { .compatible = "airoha,an7581-hsuart" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, airoha_8250_dt_ids);
+
+static struct platform_driver airoha_8250_driver = {
+ .driver = {
+ .name = "8250_airoha",
+ .of_match_table = airoha_8250_dt_ids,
+ },
+ .probe = airoha_8250_probe,
+ .remove = airoha_8250_remove,
+};
+
+module_platform_driver(airoha_8250_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Airoha UART driver");
+MODULE_AUTHOR("Benjamin Larsson <benjamin.larsson@genexis.eu>");
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 630deb7dd344..22dd114256b3 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -311,6 +311,22 @@ static const struct serial8250_config uart_config[] = {
.rxtrig_bytes = {1, 8, 16, 30},
.flags = UART_CAP_FIFO | UART_CAP_AFE,
},
+ [UART_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,
+ },
+ [UART_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 */
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index fc3e58d62233..310da7af7a49 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -337,6 +337,17 @@ 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
+ depends on 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 6d21402b4435..83257696ea8a 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
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread