openwrt/target/linux/airoha/patches-6.6/105-uart-add-en7523-support.patch

--- /dev/null
+++ b/drivers/tty/serial/8250/8250_en7523.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Airoha EN7523 driver.
+ *
+ * Copyright (c) 2022 Genexis Sweden AB
+ * Author: Benjamin Larsson <benjamin.larsson@genexis.eu>
+ */
+#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 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 things to work.
+ * 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 work.
+ *
+ * Optimally the XYD, BRD and XINCLK_DIVCNT registers could be searched to
+ * find values that gives the least error for every baud rate. But searching
+ * the space takes time and in practise only a few rates are of interest.
+ * With some value combinations not working a tested subset is used giving
+ * a usable range from 110 to 460800 baud.
+ */
+
+#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 en7523_set_uart_baud_rate (struct uart_port *port, unsigned int baud)
+{
+	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 (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);
+		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(en7523_set_uart_baud_rate);
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -338,6 +338,7 @@ static const struct of_device_id of_plat
 	{ .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,en7523-uart", .data = (void *)PORT_AIROHA, },
 	{ /* end of list */ },
 };
 MODULE_DEVICE_TABLE(of, of_platform_serial_table);
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -330,6 +330,14 @@ static const struct serial8250_config ua
 		.rxtrig_bytes	= {1, 8, 16, 30},
 		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
 	},
+	[PORT_AIROHA] = {
+		.name		= "Airoha 16550",
+		.fifo_size	= 8,
+		.tx_loadsz	= 1,
+		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01,
+		.rxtrig_bytes	= {1, 4},
+		.flags		= UART_CAP_FIFO,
+	},
 };
 
 /* Uart divisor latch read */
@@ -2880,6 +2888,12 @@ serial8250_do_set_termios(struct uart_po
 
 	serial8250_set_divisor(port, baud, quot, frac);
 
+#ifdef CONFIG_SERIAL_8250_AIROHA
+	/* Airoha SoCs have custom registers for baud rate settings */
+	if (port->type == PORT_AIROHA)
+		en7523_set_uart_baud_rate(port, baud);
+#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.
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_SERIAL_8250_PERICOM)	+= 825
 obj-$(CONFIG_SERIAL_8250_PXA)		+= 8250_pxa.o
 obj-$(CONFIG_SERIAL_8250_TEGRA)		+= 8250_tegra.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
+obj-$(CONFIG_SERIAL_8250_AIROHA)	+= 8250_en7523.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM)	+= 8250_of.o
 
 CFLAGS_8250_ingenic.o += -I$(srctree)/scripts/dtc/libfdt
--- a/include/uapi/linux/serial_reg.h
+++ b/include/uapi/linux/serial_reg.h
@@ -382,5 +382,17 @@
 #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 EN75XX uart registers
+ * Normalized because of 32 bits registers.
+ */
+#define UART_BRDL		0
+#define UART_BRDH		1
+#define UART_XINCLKDR		10
+#define UART_XYD		11
+#define UART_TXLVLCNT		12
+#define UART_RXLVLCNT		13
+#define UART_FINTLVL		14
+
 #endif /* _LINUX_SERIAL_REG_H */
 
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -45,6 +45,7 @@
 #define PORT_ALTR_16550_F128 28 /* Altera 16550 UART with 128 FIFOs */
 #define PORT_RT2880	29	/* Ralink RT2880 internal UART */
 #define PORT_16550A_FSL64 30	/* Freescale 16550 UART with 64 FIFOs */
+#define PORT_AIROHA    31	/* Airoha 16550 UART */
 
 /*
  * ARM specific type numbers.  These are not currently guaranteed
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -195,6 +195,7 @@ void serial8250_do_set_mctrl(struct uart
 void serial8250_do_set_divisor(struct uart_port *port, unsigned int baud,
 			       unsigned int quot, unsigned int quot_frac);
 int fsl8250_handle_irq(struct uart_port *port);
+int en7523_set_uart_baud_rate(struct uart_port *port, unsigned int baud);
 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);