[PATCH 0/4] serial: 8250: Add AN7581 UART support

[PATCH 0/4] serial: 8250: Add AN7581 UART support

[Christian Marangi]

This is a new version of [1] to support UART driver for
Airoha SoC.

One additional function was needed serial8250_get_baud_rate()
for the driver to work correctly for baud rate calculation.

While at it also try to clarify a long standing issue with
new UART driver when adding new ids for uart_config[].

[1] https://lore.kernel.org/all/20250209210241.2622309-1-benjamin.larsson@genexis.eu/

Changes compared to [1]:
- Fix all formal error
- Use better compatible names
- Drop unneeded header
- Drop usage of irq (it's filled by the generic function)
- General code cleanup and reorg
- Split to patch and add the UAPI map patch

Benjamin Larsson (1):
  dt-bindings: serial: 8250: Add Airoha compatibles

Christian Marangi (3):
  serial: 8250: export serial8250_get_baud_rate()
  serial: 8250: map UAPI port type to internal enum
  serial: 8250: Add Airoha SoC UART and HSUART support

 .../devicetree/bindings/serial/8250.yaml      |   5 +
 drivers/tty/serial/8250/8250.h                | 126 ++++++++++++
 drivers/tty/serial/8250/8250_airoha.c         | 190 ++++++++++++++++++
 drivers/tty/serial/8250/8250_port.c           |  95 +++++----
 drivers/tty/serial/8250/Kconfig               |  11 +
 drivers/tty/serial/8250/Makefile              |   1 +
 include/linux/serial_8250.h                   |   4 +
 7 files changed, 393 insertions(+), 39 deletions(-)
 create mode 100644 drivers/tty/serial/8250/8250_airoha.c

-- 
2.53.0

[PATCH 1/4] dt-bindings: serial: 8250: Add Airoha compatibles

[Christian Marangi]

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>
---
 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

[PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Christian Marangi]

Some driver might need to access the current baud rate to correctly
configure it.

Export the serial8250_get_baud_rate() function to limit code duplication.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/tty/serial/8250/8250_port.c | 7 ++++---
 include/linux/serial_8250.h         | 4 ++++
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 630deb7dd344..033d8fb8bb23 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2560,9 +2560,9 @@ static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
 		serial8250_do_set_divisor(port, baud, quot);
 }
 
-static unsigned int serial8250_get_baud_rate(struct uart_port *port,
-					     struct ktermios *termios,
-					     const struct ktermios *old)
+unsigned int serial8250_get_baud_rate(struct uart_port *port,
+				      struct ktermios *termios,
+				      const struct ktermios *old)
 {
 	unsigned int tolerance = port->uartclk / 100;
 	unsigned int min;
@@ -2589,6 +2589,7 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port,
 	 */
 	return uart_get_baud_rate(port, termios, old, min, max);
 }
+EXPORT_SYMBOL_GPL(serial8250_get_baud_rate);
 
 /*
  * Note in order to avoid the tty port mutex deadlock don't use the next method
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index a95b2d143d24..8d26fa2008b6 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -208,6 +208,10 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
 int serial8250_console_setup(struct uart_port *port, char *options, bool probe);
 int serial8250_console_exit(struct uart_port *port);
 
+unsigned int serial8250_get_baud_rate(struct uart_port *port,
+				      struct ktermios *termios,
+				      const struct ktermios *old);
+
 void serial8250_set_isa_configurator(void (*v)(int port, struct uart_port *up,
 					       u32 *capabilities));
 
-- 
2.53.0

[PATCH 3/4] serial: 8250: map UAPI port type to internal enum

[Christian Marangi]

There is currently some confusion when a new 8250 UART device needs to be
defined with the related index for uart_config[] to be directly defined in
UAPI header.

There isn't any specific reason to define the index directly in UAPI header
unless it's also needed to be defined for userspace usage.

To try to address this confusion and making it clear how these specific
index should be defined and where, create a dedicated enum in 8250.h
with all the current defined values in UAPI header and document how these
id should be defined.

Rename the define in 8250_port.c with the new UART_ prefix.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/tty/serial/8250/8250.h      | 122 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/8250_port.c |  72 ++++++++--------
 2 files changed, 158 insertions(+), 36 deletions(-)

diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 77fe0588fd6b..3a45f957d3a9 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -73,6 +73,128 @@ struct serial8250_config {
 	unsigned int	flags;
 };
 
+/*
+ * The uart_config[] array index is referenced and defined from index
+ * in uapi/linux/serial.h and uapi/linux/serial_core.h.
+ *
+ * This was old practice and for anything that doesn't need to support
+ * userspace, new type should be limited and added only HERE.
+ *
+ * Any UART port that requires userspace support, should define the
+ * dedicated index in the UAPI header and reference it when added
+ * to this enum table.
+ */
+enum uart_port_type {
+	/* From uapi/linux/serial.h */
+	UART_PORT_UNKNOWN		= PORT_UNKNOWN, /* 0 */
+	UART_PORT_8250			= PORT_8250,
+	UART_PORT_16450			= PORT_16450,
+	UART_PORT_16550			= PORT_16550,
+	UART_PORT_16550A		= PORT_16550A,
+	UART_PORT_CIRRUS		= PORT_CIRRUS,
+	UART_PORT_16650			= PORT_16650,
+	UART_PORT_16650V2		= PORT_16650V2,
+	UART_PORT_16750			= PORT_16750,
+	UART_PORT_STARTECH		= PORT_STARTECH,
+	UART_PORT_16C950		= PORT_16C950,
+	UART_PORT_16654			= PORT_16654,
+	UART_PORT_16850			= PORT_16850,
+	UART_PORT_RSA			= PORT_RSA, /* 13 */
+
+	/* From uapi/linux/serial_core.h (14-123) */
+	UART_PORT_NS16550A		= PORT_NS16550A, /* 14 */
+	UART_PORT_XSCALE		= PORT_XSCALE,
+	UART_PORT_RM9000		= PORT_RM9000,
+	UART_PORT_OCTEON		= PORT_OCTEON,
+	UART_PORT_AR7			= PORT_AR7,
+	UART_PORT_U6_16550A		= PORT_U6_16550A,
+	UART_PORT_TEGRA			= PORT_TEGRA,
+	UART_PORT_XR17D15X		= PORT_XR17D15X,
+	UART_PORT_LPC3220		= PORT_LPC3220,
+	UART_PORT_8250_CIR		= PORT_8250_CIR,
+	UART_PORT_XR17V35X		= PORT_XR17V35X,
+	UART_PORT_BRCM_TRUMANAGE	= PORT_BRCM_TRUMANAGE,
+	UART_PORT_ALTR_16550_F32	= PORT_ALTR_16550_F32,
+	UART_PORT_ALTR_16550_F64	= PORT_ALTR_16550_F64,
+	UART_PORT_ALTR_16550_F128	= PORT_ALTR_16550_F128,
+	UART_PORT_RT2880		= PORT_RT2880,
+	UART_PORT_16550A_FSL64		= PORT_16550A_FSL64,
+	UART_PORT_PXA			= PORT_PXA,
+	UART_PORT_AMBA			= PORT_AMBA,
+	UART_PORT_CLPS711X		= PORT_CLPS711X,
+	UART_PORT_SA1100		= PORT_SA1100,
+	UART_PORT_UART00		= PORT_UART00,
+	UART_PORT_OWL			= PORT_OWL,
+	UART_PORT_21285			= PORT_21285,
+	UART_PORT_SUNZILOG		= PORT_SUNZILOG,
+	UART_PORT_SUNSAB		= PORT_SUNSAB,
+	UART_PORT_NPCM			= PORT_NPCM,
+	UART_PORT_TEGRA_TCU		= PORT_TEGRA_TCU,
+	UART_PORT_ASPEED_VUART		= PORT_ASPEED_VUART,
+	UART_PORT_PCH_8LINE		= PORT_PCH_8LINE,
+	UART_PORT_PCH_2LINE		= PORT_PCH_2LINE,
+	UART_PORT_DZ			= PORT_DZ,
+	UART_PORT_ZS			= PORT_ZS,
+	UART_PORT_MUX			= PORT_MUX,
+	UART_PORT_ATMEL			= PORT_ATMEL,
+	UART_PORT_MAC_ZILOG		= PORT_MAC_ZILOG,
+	UART_PORT_PMAC_ZILOG		= PORT_PMAC_ZILOG,
+	UART_PORT_SCI			= PORT_SCI,
+	UART_PORT_SCIF			= PORT_SCIF,
+	UART_PORT_IRDA			= PORT_IRDA,
+	UART_PORT_IP22ZILOG		= PORT_IP22ZILOG,
+	UART_PORT_CPM			= PORT_CPM,
+	UART_PORT_MPC52xx		= PORT_MPC52xx,
+	UART_PORT_ICOM			= PORT_ICOM,
+	UART_PORT_IMX			= PORT_IMX,
+	UART_PORT_TXX9			= PORT_TXX9,
+	UART_PORT_JSM			= PORT_JSM,
+	UART_PORT_SUNHV			= PORT_SUNHV,
+	UART_PORT_UARTLITE		= PORT_UARTLITE,
+	UART_PORT_BCM7271		= PORT_BCM7271,
+	UART_PORT_SB1250_DUART		= PORT_SB1250_DUART,
+	UART_PORT_MCF			= PORT_MCF,
+	UART_PORT_SC26XX		= PORT_SC26XX,
+	UART_PORT_SCIFA			= PORT_SCIFA,
+	UART_PORT_S3C6400		= PORT_S3C6400,
+	UART_PORT_MAX3100		= PORT_MAX3100,
+	UART_PORT_TIMBUART		= PORT_TIMBUART,
+	UART_PORT_MSM			= PORT_MSM,
+	UART_PORT_BCM63XX		= PORT_BCM63XX,
+	UART_PORT_APBUART		= PORT_APBUART,
+	UART_PORT_ALTERA_JTAGUART	= PORT_ALTERA_JTAGUART,
+	UART_PORT_ALTERA_UART		= PORT_ALTERA_UART,
+	UART_PORT_SCIFB			= PORT_SCIFB,
+	UART_PORT_MAX310X		= PORT_MAX310X,
+	UART_PORT_DA830			= PORT_DA830,
+	UART_PORT_OMAP			= PORT_OMAP,
+	UART_PORT_VT8500		= PORT_VT8500,
+	UART_PORT_XUARTPS		= PORT_XUARTPS,
+	UART_PORT_AR933X		= PORT_AR933X,
+	UART_PORT_MCHP16550A		= PORT_MCHP16550A,
+	UART_PORT_ARC			= PORT_ARC,
+	UART_PORT_RP2			= PORT_RP2,
+	UART_PORT_LPUART		= PORT_LPUART,
+	UART_PORT_HSCIF			= PORT_HSCIF,
+	UART_PORT_ASC			= PORT_ASC,
+	UART_PORT_MEN_Z135		= PORT_MEN_Z135,
+	UART_PORT_SC16IS7XX		= PORT_SC16IS7XX,
+	UART_PORT_MESON			= PORT_MESON,
+	UART_PORT_DIGICOLOR		= PORT_DIGICOLOR,
+	UART_PORT_SPRD			= PORT_SPRD,
+	UART_PORT_STM32			= PORT_STM32,
+	UART_PORT_MVEBU			= PORT_MVEBU,
+	UART_PORT_PIC32			= PORT_PIC32,
+	UART_PORT_MPS2UART		= PORT_MPS2UART,
+	UART_PORT_MTK_BTIF		= PORT_MTK_BTIF,
+	UART_PORT_RDA			= PORT_RDA,
+	UART_PORT_MLB_USIO		= PORT_MLB_USIO,
+	UART_PORT_SIFIVE_V0		= PORT_SIFIVE_V0,
+	UART_PORT_SUNIX			= PORT_SUNIX,
+	UART_PORT_LINFLEXUART		= PORT_LINFLEXUART,
+	UART_PORT_SUNPLUS		= PORT_SUNPLUS, /* 123 */
+};
+
 #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_port.c b/drivers/tty/serial/8250/8250_port.c
index 033d8fb8bb23..a0b80324a559 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -43,27 +43,27 @@
  * Here we define the default xmit fifo size used for each type of UART.
  */
 static const struct serial8250_config uart_config[] = {
-	[PORT_UNKNOWN] = {
+	[UART_PORT_UNKNOWN] = {
 		.name		= "unknown",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_8250] = {
+	[UART_PORT_8250] = {
 		.name		= "8250",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_16450] = {
+	[UART_PORT_16450] = {
 		.name		= "16450",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_16550] = {
+	[UART_PORT_16550] = {
 		.name		= "16550",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_16550A] = {
+	[UART_PORT_16550A] = {
 		.name		= "16550A",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -71,18 +71,18 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_CIRRUS] = {
+	[UART_PORT_CIRRUS] = {
 		.name		= "Cirrus",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_16650] = {
+	[UART_PORT_16650] = {
 		.name		= "ST16650",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
 	},
-	[PORT_16650V2] = {
+	[UART_PORT_16650V2] = {
 		.name		= "ST16650V2",
 		.fifo_size	= 32,
 		.tx_loadsz	= 16,
@@ -91,7 +91,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {8, 16, 24, 28},
 		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
 	},
-	[PORT_16750] = {
+	[UART_PORT_16750] = {
 		.name		= "TI16750",
 		.fifo_size	= 64,
 		.tx_loadsz	= 64,
@@ -100,12 +100,12 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 16, 32, 56},
 		.flags		= UART_CAP_FIFO | UART_CAP_SLEEP | UART_CAP_AFE,
 	},
-	[PORT_STARTECH] = {
+	[UART_PORT_STARTECH] = {
 		.name		= "Startech",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1,
 	},
-	[PORT_16C950] = {
+	[UART_PORT_16C950] = {
 		.name		= "16C950/954",
 		.fifo_size	= 128,
 		.tx_loadsz	= 128,
@@ -114,7 +114,7 @@ static const struct serial8250_config uart_config[] = {
 		/* UART_CAP_EFR breaks billionon CF bluetooth card. */
 		.flags		= UART_CAP_FIFO | UART_CAP_SLEEP,
 	},
-	[PORT_16654] = {
+	[UART_PORT_16654] = {
 		.name		= "ST16654",
 		.fifo_size	= 64,
 		.tx_loadsz	= 32,
@@ -123,49 +123,49 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {8, 16, 56, 60},
 		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
 	},
-	[PORT_16850] = {
+	[UART_PORT_16850] = {
 		.name		= "XR16850",
 		.fifo_size	= 128,
 		.tx_loadsz	= 128,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
 	},
-	[PORT_RSA] = {
+	[UART_PORT_RSA] = {
 		.name		= "RSA",
 		.fifo_size	= 2048,
 		.tx_loadsz	= 2048,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_11,
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_NS16550A] = {
+	[UART_PORT_NS16550A] = {
 		.name		= "NS16550A",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO | UART_NATSEMI,
 	},
-	[PORT_XSCALE] = {
+	[UART_PORT_XSCALE] = {
 		.name		= "XScale",
 		.fifo_size	= 32,
 		.tx_loadsz	= 32,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO | UART_CAP_UUE | UART_CAP_RTOIE,
 	},
-	[PORT_OCTEON] = {
+	[UART_PORT_OCTEON] = {
 		.name		= "OCTEON",
 		.fifo_size	= 64,
 		.tx_loadsz	= 64,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_U6_16550A] = {
+	[UART_PORT_U6_16550A] = {
 		.name		= "U6_16550A",
 		.fifo_size	= 64,
 		.tx_loadsz	= 64,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
 	},
-	[PORT_TEGRA] = {
+	[UART_PORT_TEGRA] = {
 		.name		= "Tegra",
 		.fifo_size	= 32,
 		.tx_loadsz	= 8,
@@ -174,7 +174,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO | UART_CAP_RTOIE,
 	},
-	[PORT_XR17D15X] = {
+	[UART_PORT_XR17D15X] = {
 		.name		= "XR17D15X",
 		.fifo_size	= 64,
 		.tx_loadsz	= 64,
@@ -182,7 +182,7 @@ static const struct serial8250_config uart_config[] = {
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR |
 				  UART_CAP_SLEEP,
 	},
-	[PORT_XR17V35X] = {
+	[UART_PORT_XR17V35X] = {
 		.name		= "XR17V35X",
 		.fifo_size	= 256,
 		.tx_loadsz	= 256,
@@ -191,7 +191,7 @@ static const struct serial8250_config uart_config[] = {
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR |
 				  UART_CAP_SLEEP,
 	},
-	[PORT_LPC3220] = {
+	[UART_PORT_LPC3220] = {
 		.name		= "LPC3220",
 		.fifo_size	= 64,
 		.tx_loadsz	= 32,
@@ -199,16 +199,16 @@ static const struct serial8250_config uart_config[] = {
 				  UART_FCR_R_TRIG_00 | UART_FCR_T_TRIG_00,
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_BRCM_TRUMANAGE] = {
+	[UART_PORT_BRCM_TRUMANAGE] = {
 		.name		= "TruManage",
 		.fifo_size	= 1,
 		.tx_loadsz	= 1024,
 		.flags		= UART_CAP_HFIFO,
 	},
-	[PORT_8250_CIR] = {
+	[UART_PORT_8250_CIR] = {
 		.name		= "CIR port"
 	},
-	[PORT_ALTR_16550_F32] = {
+	[UART_PORT_ALTR_16550_F32] = {
 		.name		= "Altera 16550 FIFO32",
 		.fifo_size	= 32,
 		.tx_loadsz	= 32,
@@ -216,7 +216,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 8, 16, 30},
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
 	},
-	[PORT_ALTR_16550_F64] = {
+	[UART_PORT_ALTR_16550_F64] = {
 		.name		= "Altera 16550 FIFO64",
 		.fifo_size	= 64,
 		.tx_loadsz	= 64,
@@ -224,7 +224,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 16, 32, 62},
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
 	},
-	[PORT_ALTR_16550_F128] = {
+	[UART_PORT_ALTR_16550_F128] = {
 		.name		= "Altera 16550 FIFO128",
 		.fifo_size	= 128,
 		.tx_loadsz	= 128,
@@ -237,7 +237,7 @@ static const struct serial8250_config uart_config[] = {
 	 * workaround of errata A-008006 which states that tx_loadsz should
 	 * be configured less than Maximum supported fifo bytes.
 	 */
-	[PORT_16550A_FSL64] = {
+	[UART_PORT_16550A_FSL64] = {
 		.name		= "16550A_FSL64",
 		.fifo_size	= 64,
 		.tx_loadsz	= 63,
@@ -245,7 +245,7 @@ static const struct serial8250_config uart_config[] = {
 				  UART_FCR7_64BYTE,
 		.flags		= UART_CAP_FIFO | UART_CAP_NOTEMT,
 	},
-	[PORT_RT2880] = {
+	[UART_PORT_RT2880] = {
 		.name		= "Palmchip BK-3103",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -253,7 +253,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_DA830] = {
+	[UART_PORT_DA830] = {
 		.name		= "TI DA8xx/66AK2x",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -262,7 +262,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
 	},
-	[PORT_MTK_BTIF] = {
+	[UART_PORT_MTK_BTIF] = {
 		.name		= "MediaTek BTIF",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -270,7 +270,7 @@ static const struct serial8250_config uart_config[] = {
 				  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_NPCM] = {
+	[UART_PORT_NPCM] = {
 		.name		= "Nuvoton 16550",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -279,7 +279,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_SUNIX] = {
+	[UART_PORT_SUNIX] = {
 		.name		= "Sunix",
 		.fifo_size	= 128,
 		.tx_loadsz	= 128,
@@ -287,7 +287,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 32, 64, 112},
 		.flags		= UART_CAP_FIFO | UART_CAP_SLEEP,
 	},
-	[PORT_ASPEED_VUART] = {
+	[UART_PORT_ASPEED_VUART] = {
 		.name		= "ASPEED VUART",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
@@ -295,7 +295,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO,
 	},
-	[PORT_MCHP16550A] = {
+	[UART_PORT_MCHP16550A] = {
 		.name           = "MCHP16550A",
 		.fifo_size      = 256,
 		.tx_loadsz      = 256,
@@ -303,7 +303,7 @@ static const struct serial8250_config uart_config[] = {
 		.rxtrig_bytes   = {2, 66, 130, 194},
 		.flags          = UART_CAP_FIFO,
 	},
-	[PORT_BCM7271] = {
+	[UART_PORT_BCM7271] = {
 		.name		= "Broadcom BCM7271 UART",
 		.fifo_size	= 32,
 		.tx_loadsz	= 32,
-- 
2.53.0

[PATCH 4/4] serial: 8250: Add Airoha SoC UART and HSUART support

[Christian Marangi]

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        |   4 +
 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, 222 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 3a45f957d3a9..a0dec4161240 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -193,6 +193,10 @@ enum uart_port_type {
 	UART_PORT_SUNIX			= PORT_SUNIX,
 	UART_PORT_LINFLEXUART		= PORT_LINFLEXUART,
 	UART_PORT_SUNPLUS		= PORT_SUNPLUS, /* 123 */
+
+	/* Internal 8250 only */
+	UART_PORT_AIROHA		= 124,
+	UART_PORT_AIROHA_HS		= 125,
 };
 
 #define UART_CAP_FIFO	BIT(8)	/* UART has FIFO */
diff --git a/drivers/tty/serial/8250/8250_airoha.c b/drivers/tty/serial/8250/8250_airoha.c
new file mode 100644
index 000000000000..9ec98cd8de43
--- /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/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
+
+struct airoha_8250_priv {
+	int line;
+};
+
+struct airoha_8250_data {
+	unsigned int type;
+};
+
+struct airoha_8250_clk_div_info {
+	int div;
+	int 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 const int clock_div_tab[] = { 10, 4, 2};
+static const int clock_div_reg[] = {  4, 2, 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_termios(struct uart_port *port, struct ktermios *termios,
+			       const struct ktermios *old)
+{
+	const struct airoha_8250_clk_div_info *clk_div_info;
+	struct uart_8250_port *up = up_to_u8250p(port);
+	unsigned int xyd_x, nom, denom;
+	unsigned int baud;
+	int i;
+
+	serial8250_do_set_termios(port, termios, old);
+
+	baud = serial8250_get_baud_rate(port, termios, old);
+
+	/* 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.
+	 */
+	for (i = 0 ; i < ARRAY_SIZE(airoha_clk_div_info) ; i++) {
+		clk_div_info = &airoha_clk_div_info[i];
+
+		denom = (XINDIV_CLOCK / 40) / clk_div_info->div;
+		nom = baud * (XYD_Y / 40);
+		xyd_x = ((nom / denom) << 4);
+		/* For the HSUART xyd_x needs to be scaled by a factor of 2 */
+		if (port->type == UART_PORT_AIROHA_HS)
+			xyd_x = xyd_x >> 1;
+		if (xyd_x < XYD_Y)
+			break;
+	}
+
+	serial_port_out(port, UART_AIROHA_XINCLKDR, clk_div_info->mask);
+	serial_port_out(port, UART_AIROHA_XYD, (xyd_x << 16) | XYD_Y);
+
+	/* unset DLAB */
+	serial_port_out(port, UART_LCR, up->lcr);
+}
+
+static int airoha_8250_probe(struct platform_device *pdev)
+{
+	const struct airoha_8250_data *data;
+	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;
+
+	data = device_get_match_data(dev);
+
+	uart.port.dev = dev;
+	uart.port.type = data->type;
+	uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT |
+			  UPF_FIXED_TYPE | UPF_IOREMAP;
+	uart.port.set_termios = airoha_set_termios;
+	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 airoha_8250_data en7523_data = {
+	.type = UART_PORT_AIROHA,
+};
+
+static const struct airoha_8250_data an7581_hs_data = {
+	.type = UART_PORT_AIROHA_HS,
+};
+
+static const struct of_device_id airoha_8250_dt_ids[] = {
+	{ .compatible = "airoha,en7523-uart", .data = &en7523_data, },
+	{ .compatible = "airoha,an7581-hsuart", .data = &an7581_hs_data, },
+	{ },
+};
+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 a0b80324a559..29f0245264ec 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

Re: [PATCH 3/4] serial: 8250: map UAPI port type to internal enum

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The new documentation guidelines encourage a split-brain ID registry that will cause integer collisions between internal 8250 port types and global UAPI port types.
--

--- Patch [3]: [PATCH 3/4] serial: 8250: map UAPI port type to internal enum ---
commit d2ffed5bdc0925967ba25a551f7c1657761a9cab
Author: Christian Marangi <ansuelsmth@gmail.com>

serial: 8250: map UAPI port type to internal enum

This commit maps the UAPI port types to an internal enum in the 8250 driver.
It creates a dedicated enum in 8250.h with all current UAPI values and documents
how new indexes should be defined. It also renames definitions in 8250_port.c
with a new UART_ prefix.

> diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
> --- a/drivers/tty/serial/8250/8250.h
> +++ b/drivers/tty/serial/8250/8250.h
> @@ -73,6 +73,128 @@ struct serial8250_config {
>  	unsigned int	flags;
>  };
>  
> +/*
> + * The uart_config[] array index is referenced and defined from index
> + * in uapi/linux/serial.h and uapi/linux/serial_core.h.
> + *
> + * This was old practice and for anything that doesn't need to support
> + * userspace, new type should be limited and added only HERE.
> + *
> + * Any UART port that requires userspace support, should define the
> + * dedicated index in the UAPI header and reference it when added
> + * to this enum table.
> + */
> +enum uart_port_type {

[Severity: High]
Does this new documentation encourage a split-brain ID registry that could
cause integer collisions between internal 8250 port types and global UAPI
port types?

If a developer follows this documentation and defines a new internal port type
at the end of enum uart_port_type (e.g., getting value 124), what happens if
another subsystem concurrently adds a port to <uapi/linux/serial_core.h> that
also receives value 124?

Since the port->type field is a globally shared namespace across all serial
drivers, driver-local enum values that are not offset into a disjoint range
might collide with new UAPI additions. This could manifest as compile-time
errors when the uart_config[] array is populated, or runtime ABI
misidentification by userspace tools if setserial treats an internal 8250
port as a completely different architecture's port.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709205656.319531-1-ansuelsmth@gmail.com?part=3

Re: [PATCH 4/4] serial: 8250: Add Airoha SoC UART and HSUART support

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [High] Hardware registers are accessed without holding the port lock, causing a critical race condition with interrupt handlers.
- [High] Integer overflow and out-of-bounds truncation in custom baud rate calculation.
- [High] Missing NULL pointer check for device_get_match_data() result.
- [Low] Unused static const arrays (dead code).
--

--- Patch [4]: [PATCH 4/4] serial: 8250: Add Airoha SoC UART and HSUART support ---
commit 787398b7c15179f8d67914a09402fbd411a20806
Author: Christian Marangi <ansuelsmth@gmail.com>

serial: 8250: Add Airoha SoC UART and HSUART support

This commit adds support for Airoha AN7523 UART and AN7581 HSUART.
These implement a standard 16550 UART with custom logic for baud rate handling.

> diff --git a/drivers/tty/serial/8250/8250_airoha.c b/drivers/tty/serial/8250/8250_airoha.c
> new file mode 100644
> index 0000000000000..9ec98cd8de438
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_airoha.c
[ ... ]
> +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 const int clock_div_tab[] = { 10, 4, 2};
> +static const int clock_div_reg[] = {  4, 2, 1};

[Severity: Low]
Are these arrays used anywhere in the driver? It looks like the implementation
relies on airoha_clk_div_info instead, making these dead code.

> +
> +/*
> + * Airoha UART baud rate calculation logic
[ ... ]
> +static void airoha_set_termios(struct uart_port *port, struct ktermios *termios,
> +			       const struct ktermios *old)
> +{
> +	const struct airoha_8250_clk_div_info *clk_div_info;
> +	struct uart_8250_port *up = up_to_u8250p(port);
> +	unsigned int xyd_x, nom, denom;
> +	unsigned int baud;
> +	int i;
> +
> +	serial8250_do_set_termios(port, termios, old);
> +
> +	baud = serial8250_get_baud_rate(port, termios, old);
> +
> +	/* Set DLAB to access the baud rate divider registers (BRDH, BRDL) */
> +	serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);

[Severity: High]
Does this sequence leave the port registers unprotected?

Looking at serial8250_do_set_termios(), it acquires and then releases the
port lock. Modifying UART_LCR here to set the DLAB bit without holding the
port lock leaves a race window.

If a UART RX or TX interrupt fires concurrently, the interrupt handler
(serial8250_handle_irq) will acquire the port lock and attempt to read UART_RX
or write UART_TX at offset 0. Since DLAB=1, offset 0 becomes the UART_DLL
register, which could lead to silently overwriting the baud rate divisor or
reading corrupted data.

Additionally, does this access registers without an active runtime PM reference?

> +
> +	/* 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.
> +	 */
> +	for (i = 0 ; i < ARRAY_SIZE(airoha_clk_div_info) ; i++) {
> +		clk_div_info = &airoha_clk_div_info[i];
> +
> +		denom = (XINDIV_CLOCK / 40) / clk_div_info->div;
> +		nom = baud * (XYD_Y / 40);
> +		xyd_x = ((nom / denom) << 4);

[Severity: High]
Could the calculation for nom silently overflow on high baud rates?

If baud is very high (e.g., 3,000,000 or 4,000,000 for HSUARTs), multiplying
it by 1625 (XYD_Y / 40) exceeds the maximum capacity of a 32-bit unsigned int,
resulting in an incorrectly calculated baud rate.

> +		/* For the HSUART xyd_x needs to be scaled by a factor of 2 */
> +		if (port->type == UART_PORT_AIROHA_HS)
> +			xyd_x = xyd_x >> 1;
> +		if (xyd_x < XYD_Y)
> +			break;
> +	}
> +
> +	serial_port_out(port, UART_AIROHA_XINCLKDR, clk_div_info->mask);
> +	serial_port_out(port, UART_AIROHA_XYD, (xyd_x << 16) | XYD_Y);

[Severity: High]
If the loop terminates without finding a valid divider and xyd_x remains
large, will the left shift of xyd_x by 16 silently overflow a 32-bit integer
here before the write to UART_AIROHA_XYD?

> +
> +	/* unset DLAB */
> +	serial_port_out(port, UART_LCR, up->lcr);
> +}
> +
> +static int airoha_8250_probe(struct platform_device *pdev)
> +{
> +	const struct airoha_8250_data *data;
> +	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;
> +
> +	data = device_get_match_data(dev);
> +
> +	uart.port.dev = dev;
> +	uart.port.type = data->type;

[Severity: High]
Is it possible for device_get_match_data() to return NULL here?

If a platform device is manually bound via sysfs without a Device Tree node,
it would lack OF match data, causing device_get_match_data() to return NULL.
This would lead to a NULL pointer dereference when accessing data->type.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709205656.319531-1-ansuelsmth@gmail.com?part=4

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Andy Shevchenko]

On Thu, Jul 09, 2026 at 10:56:50PM +0200, Christian Marangi wrote:
> Some driver might need to access the current baud rate to correctly
> configure it.
> 
> Export the serial8250_get_baud_rate() function to limit code duplication.

Why?

We have _get_divisor() / _set_divisor() for exactly that purpose, no?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 3/4] serial: 8250: map UAPI port type to internal enum

[Andy Shevchenko]

On Thu, Jul 09, 2026 at 10:56:51PM +0200, Christian Marangi wrote:
> There is currently some confusion when a new 8250 UART device needs to be
> defined with the related index for uart_config[] to be directly defined in
> UAPI header.
> 
> There isn't any specific reason to define the index directly in UAPI header
> unless it's also needed to be defined for userspace usage.
> 
> To try to address this confusion and making it clear how these specific
> index should be defined and where, create a dedicated enum in 8250.h
> with all the current defined values in UAPI header and document how these
> id should be defined.
> 
> Rename the define in 8250_port.c with the new UART_ prefix.

This will bring a wide field for the all possible conflicts and doesn't really
solve the issue. Why not simply kill the UAPI part of the definitions for good?
(Move the all, except the first 13) to be internal to the kernel.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Christian Marangi]

On Fri, Jul 10, 2026 at 12:35:02AM +0300, Andy Shevchenko wrote:
> On Thu, Jul 09, 2026 at 10:56:50PM +0200, Christian Marangi wrote:
> > Some driver might need to access the current baud rate to correctly
> > configure it.
> > 
> > Export the serial8250_get_baud_rate() function to limit code duplication.
> 
> Why?
> 
> We have _get_divisor() / _set_divisor() for exactly that purpose, no?
> 

I can only see set and I'm not following how that helps with any driver
that needs to get the baud_rate?

-- 
	Ansuel

Re: [PATCH 3/4] serial: 8250: map UAPI port type to internal enum

[Christian Marangi]

On Fri, Jul 10, 2026 at 12:37:48AM +0300, Andy Shevchenko wrote:
> On Thu, Jul 09, 2026 at 10:56:51PM +0200, Christian Marangi wrote:
> > There is currently some confusion when a new 8250 UART device needs to be
> > defined with the related index for uart_config[] to be directly defined in
> > UAPI header.
> > 
> > There isn't any specific reason to define the index directly in UAPI header
> > unless it's also needed to be defined for userspace usage.
> > 
> > To try to address this confusion and making it clear how these specific
> > index should be defined and where, create a dedicated enum in 8250.h
> > with all the current defined values in UAPI header and document how these
> > id should be defined.
> > 
> > Rename the define in 8250_port.c with the new UART_ prefix.
> 
> This will bring a wide field for the all possible conflicts and doesn't really
> solve the issue. Why not simply kill the UAPI part of the definitions for good?
> (Move the all, except the first 13) to be internal to the kernel.
> 

I mean... With correct review from maintainers, conflict won't happen. I don't
feel it's that easy to kill UAPI header... userspace stuff and we don't
kill userspace.

The previous suggested solution was to stop declaring stuff in UAPI header
and start declaring in the internal header making the situation even worse
and error prone with id conflict. This can really be prevent only by
correct review of the change. (or keep using UAPI)

Maybe other have better ideas on this. On net we have a similar problem and
the implementation is mostly similar with duplicated reference and some
BUILD_BUG magic.

-- 
	Ansuel

Re: [PATCH 4/4] serial: 8250: Add Airoha SoC UART and HSUART support

[Jiri Slaby]

On 09. 07. 26, 22:56, Christian Marangi wrote:
...
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_airoha.c
> @@ -0,0 +1,190 @@
...
> +struct airoha_8250_priv {
> +	int line;
> +};
> +
> +struct airoha_8250_data {

Do you need this struct at all? Can't you pass the type as data directly 
(using cast)?

> +	unsigned int type;
> +};
> +
> +struct airoha_8250_clk_div_info {
> +	int div;
> +	int mask;

Perhaps make them unsigned to avoid signed arithmetics?

> +};
> +
> +#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 const int clock_div_tab[] = { 10, 4, 2};
> +static const int clock_div_reg[] = {  4, 2, 1};

unsigned?

> +
> +/*
> + * 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_termios(struct uart_port *port, struct ktermios *termios,
> +			       const struct ktermios *old)
> +{
> +	const struct airoha_8250_clk_div_info *clk_div_info;
> +	struct uart_8250_port *up = up_to_u8250p(port);
> +	unsigned int xyd_x, nom, denom;
> +	unsigned int baud;
> +	int i;
> +
> +	serial8250_do_set_termios(port, termios, old);
> +
> +	baud = serial8250_get_baud_rate(port, termios, old);
> +
> +	/* 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.
> +	 */
> +	for (i = 0 ; i < ARRAY_SIZE(airoha_clk_div_info) ; i++) {
> +		clk_div_info = &airoha_clk_div_info[i];
> +
> +		denom = (XINDIV_CLOCK / 40) / clk_div_info->div;
> +		nom = baud * (XYD_Y / 40);

Are these "/ 40" to avoid overflow? Add a comment.

> +		xyd_x = ((nom / denom) << 4);

* don't you want to round to closest instead of down?
* I don't understand the purpose of the shift though.

> +		/* For the HSUART xyd_x needs to be scaled by a factor of 2 */
> +		if (port->type == UART_PORT_AIROHA_HS)
> +			xyd_x = xyd_x >> 1;

Do not use shifts for div/mul.

> +		if (xyd_x < XYD_Y)
> +			break;
> +	}
> +
> +	serial_port_out(port, UART_AIROHA_XINCLKDR, clk_div_info->mask);
> +	serial_port_out(port, UART_AIROHA_XYD, (xyd_x << 16) | XYD_Y);
> +
> +	/* unset DLAB */
> +	serial_port_out(port, UART_LCR, up->lcr);
> +}

thanks,
-- 
js
suse labs

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Ilpo Järvinen]

On Thu, 9 Jul 2026, Christian Marangi wrote:

> Some driver might need to access the current baud rate to correctly
> configure it.
> 
> Export the serial8250_get_baud_rate() function to limit code duplication.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> ---
>  drivers/tty/serial/8250/8250_port.c | 7 ++++---
>  include/linux/serial_8250.h         | 4 ++++
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 630deb7dd344..033d8fb8bb23 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2560,9 +2560,9 @@ static void serial8250_set_divisor(struct uart_port *port, unsigned int baud,
>  		serial8250_do_set_divisor(port, baud, quot);
>  }
>  
> -static unsigned int serial8250_get_baud_rate(struct uart_port *port,
> -					     struct ktermios *termios,
> -					     const struct ktermios *old)
> +unsigned int serial8250_get_baud_rate(struct uart_port *port,
> +				      struct ktermios *termios,
> +				      const struct ktermios *old)
>  {
>  	unsigned int tolerance = port->uartclk / 100;
>  	unsigned int min;
> @@ -2589,6 +2589,7 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port,
>  	 */
>  	return uart_get_baud_rate(port, termios, old, min, max);
>  }
> +EXPORT_SYMBOL_GPL(serial8250_get_baud_rate);

Please put newly exported things into SERIAL_8250 namespace.

-- 
 i.

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Andy Shevchenko]

On Thu, Jul 09, 2026 at 11:39:32PM +0200, Christian Marangi wrote:
> On Fri, Jul 10, 2026 at 12:35:02AM +0300, Andy Shevchenko wrote:
> > On Thu, Jul 09, 2026 at 10:56:50PM +0200, Christian Marangi wrote:
> > > Some driver might need to access the current baud rate to correctly
> > > configure it.
> > > 
> > > Export the serial8250_get_baud_rate() function to limit code duplication.
> > 
> > Why?
> > 
> > We have _get_divisor() / _set_divisor() for exactly that purpose, no?
> 
> I can only see set and I'm not following how that helps with any driver
> that needs to get the baud_rate?

You operate on the divisor settings instead of baud rate. Otherwise, can
you elaborate why no other (out of dozens!) driver needs this? What do
you try to achieve with the baud rate settings exactly?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Christian Marangi]

On Fri, Jul 10, 2026 at 11:20:48AM +0300, Andy Shevchenko wrote:
> On Thu, Jul 09, 2026 at 11:39:32PM +0200, Christian Marangi wrote:
> > On Fri, Jul 10, 2026 at 12:35:02AM +0300, Andy Shevchenko wrote:
> > > On Thu, Jul 09, 2026 at 10:56:50PM +0200, Christian Marangi wrote:
> > > > Some driver might need to access the current baud rate to correctly
> > > > configure it.
> > > > 
> > > > Export the serial8250_get_baud_rate() function to limit code duplication.
> > > 
> > > Why?
> > > 
> > > We have _get_divisor() / _set_divisor() for exactly that purpose, no?
> > 
> > I can only see set and I'm not following how that helps with any driver
> > that needs to get the baud_rate?
> 
> You operate on the divisor settings instead of baud rate. Otherwise, can
> you elaborate why no other (out of dozens!) driver needs this? What do
> you try to achieve with the baud rate settings exactly?
> 

Ok it wasn't easy to find but you were referring to the .set_divisor and
.get_divisor. Now it's clear. Yes I guess I can use them instead of
exporting this function.

Sorry for the noise and thanks for the suggestion! 

-- 
	Ansuel

Re: [PATCH 2/4] serial: 8250: export serial8250_get_baud_rate()

[Andy Shevchenko]

On Fri, Jul 10, 2026 at 10:49:27AM +0200, Christian Marangi wrote:
> On Fri, Jul 10, 2026 at 11:20:48AM +0300, Andy Shevchenko wrote:
> > On Thu, Jul 09, 2026 at 11:39:32PM +0200, Christian Marangi wrote:
> > > On Fri, Jul 10, 2026 at 12:35:02AM +0300, Andy Shevchenko wrote:
> > > > On Thu, Jul 09, 2026 at 10:56:50PM +0200, Christian Marangi wrote:
> > > > > Some driver might need to access the current baud rate to correctly
> > > > > configure it.
> > > > > 
> > > > > Export the serial8250_get_baud_rate() function to limit code duplication.
> > > > 
> > > > Why?
> > > > 
> > > > We have _get_divisor() / _set_divisor() for exactly that purpose, no?
> > > 
> > > I can only see set and I'm not following how that helps with any driver
> > > that needs to get the baud_rate?
> > 
> > You operate on the divisor settings instead of baud rate. Otherwise, can
> > you elaborate why no other (out of dozens!) driver needs this? What do
> > you try to achieve with the baud rate settings exactly?
> 
> Ok it wasn't easy to find but you were referring to the .set_divisor and
> .get_divisor. Now it's clear. Yes I guess I can use them instead of
> exporting this function.
> 
> Sorry for the noise and thanks for the suggestion! 

Ah, it was me a bit unclear, By _*_divisor() I referred to the wrappers
on top of .set_divisor() and .get_divisor(), I should have spelled that
more clearly. In any case the driver is suppose to fill callbacks and 8250
set_termios() will use that.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 3/4] serial: 8250: map UAPI port type to internal enum

[Andy Shevchenko]

On Thu, Jul 09, 2026 at 11:46:02PM +0200, Christian Marangi wrote:
> On Fri, Jul 10, 2026 at 12:37:48AM +0300, Andy Shevchenko wrote:
> > On Thu, Jul 09, 2026 at 10:56:51PM +0200, Christian Marangi wrote:
> > > There is currently some confusion when a new 8250 UART device needs to be
> > > defined with the related index for uart_config[] to be directly defined in
> > > UAPI header.
> > > 
> > > There isn't any specific reason to define the index directly in UAPI header
> > > unless it's also needed to be defined for userspace usage.
> > > 
> > > To try to address this confusion and making it clear how these specific
> > > index should be defined and where, create a dedicated enum in 8250.h
> > > with all the current defined values in UAPI header and document how these
> > > id should be defined.
> > > 
> > > Rename the define in 8250_port.c with the new UART_ prefix.
> > 
> > This will bring a wide field for the all possible conflicts and doesn't really
> > solve the issue. Why not simply kill the UAPI part of the definitions for good?
> > (Move the all, except the first 13) to be internal to the kernel.
> 
> I mean... With correct review from maintainers, conflict won't happen. I don't
> feel it's that easy to kill UAPI header... userspace stuff and we don't
> kill userspace.
> 
> The previous suggested solution was to stop declaring stuff in UAPI header
> and start declaring in the internal header making the situation even worse
> and error prone with id conflict. This can really be prevent only by
> correct review of the change. (or keep using UAPI)
> 
> Maybe other have better ideas on this. On net we have a similar problem and
> the implementation is mostly similar with duplicated reference and some
> BUILD_BUG magic.

The whole point of UAPI list of the supported types of the ports is busted from
the very first case when we start re-using gaps. Meaning that if there is any
current userspace software that relies on that information, it's already in a mess
state. There is a Debian source code browser, you can check how many programs
use that list for something real (behind the assigning types to the unknown ports).
I believe none. And the assigning unknown port should not be considered valuable
these days as we expect to have kernel drivers for most of the modern HW.
That's why I just recommend to find a great common denominator and leave only
those (and I think this split is exactly between the files in UAPI) in UAPI
and hide the rest completely from the user space. Yes, big change on paper,
but with 99.99% probability no functional change at all at the end of the day.

Submit and RFC patch.


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/4] dt-bindings: serial: 8250: Add Airoha compatibles

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 1331 bytes --]

On Thu, Jul 09, 2026 at 10:56:49PM +0200, Christian Marangi wrote:
> 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>
> ---
>  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

Acked-by: Conor Dooley <conor.dooley@microchip.com>
pw-bot: not-applicable

> +      - const: airoha,an7581-hsuart
>        - const: nvidia,tegra20-uart
>        - const: nxp,lpc3220-uart
>        - items:
> -- 
> 2.53.0
> 

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