drivers: serial: Add in UART for ADI SC5XX-family processors

Co-developed-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@timesys.com>
Co-developed-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Vasileios Bimpikas <vasileios.bimpikas@analog.com>
Signed-off-by: Utsav Agarwal <utsav.agarwal@analog.com>
Signed-off-by: Arturs Artamonovs <arturs.artamonovs@analog.com>
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>

drivers/serial/Makefile

@@ -65,3 +65,4 @@ obj-$(CONFIG_S5P4418_PL011_SERIAL) += serial_s5p4418_pl011.o
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o
 endif
+obj-$(CONFIG_UART4_SERIAL) += serial_adi_uart4.o

drivers/serial/serial_adi_uart4.c

@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * (C) Copyright 2022 - Analog Devices, Inc.
+ *
+ * Written and/or maintained by Timesys Corporation
+ *
+ * Converted to driver model by Nathan Barrett-Morrison
+ *
+ * Contact: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
+ * Contact: Greg Malysa <greg.malysa@timesys.com>
+ *
+ */
+
+#include <clk.h>
+#include <dm.h>
+#include <serial.h>
+#include <asm/io.h>
+#include <dm/device_compat.h>
+#include <linux/bitops.h>
+
+/*
+ * UART4 Masks
+ */
+
+/* UART_CONTROL */
+#define UEN			BIT(0)
+#define LOOP_ENA		BIT(1)
+#define UMOD			(3 << 4)
+#define UMOD_UART		(0 << 4)
+#define UMOD_MDB		BIT(4)
+#define UMOD_IRDA		BIT(4)
+#define WLS			(3 << 8)
+#define WLS_5			(0 << 8)
+#define WLS_6			BIT(8)
+#define WLS_7			(2 << 8)
+#define WLS_8			(3 << 8)
+#define STB			BIT(12)
+#define STBH			BIT(13)
+#define PEN			BIT(14)
+#define EPS			BIT(15)
+#define STP			BIT(16)
+#define FPE			BIT(17)
+#define FFE			BIT(18)
+#define SB			BIT(19)
+#define FCPOL			BIT(22)
+#define RPOLC			BIT(23)
+#define TPOLC			BIT(24)
+#define MRTS			BIT(25)
+#define XOFF			BIT(26)
+#define ARTS			BIT(27)
+#define ACTS			BIT(28)
+#define RFIT			BIT(29)
+#define RFRT			BIT(30)
+
+/* UART_STATUS */
+#define DR			BIT(0)
+#define OE			BIT(1)
+#define PE			BIT(2)
+#define FE			BIT(3)
+#define BI			BIT(4)
+#define THRE			BIT(5)
+#define TEMT			BIT(7)
+#define TFI			BIT(8)
+#define ASTKY			BIT(9)
+#define ADDR			BIT(10)
+#define RO			BIT(11)
+#define SCTS			BIT(12)
+#define CTS			BIT(16)
+#define RFCS			BIT(17)
+
+/* UART_EMASK */
+#define ERBFI			BIT(0)
+#define ETBEI			BIT(1)
+#define ELSI			BIT(2)
+#define EDSSI			BIT(3)
+#define EDTPTI			BIT(4)
+#define ETFI			BIT(5)
+#define ERFCI			BIT(6)
+#define EAWI			BIT(7)
+#define ERXS			BIT(8)
+#define ETXS			BIT(9)
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct uart4_reg {
+	u32 revid;
+	u32 control;
+	u32 status;
+	u32 scr;
+	u32 clock;
+	u32 emask;
+	u32 emaskst;
+	u32 emaskcl;
+	u32 rbr;
+	u32 thr;
+	u32 taip;
+	u32 tsr;
+	u32 rsr;
+	u32 txdiv_cnt;
+	u32 rxdiv_cnt;
+};
+
+struct adi_uart4_platdata {
+	// Hardware registers
+	struct uart4_reg *regs;
+
+	// Enable divide-by-one baud rate setting
+	bool edbo;
+};
+
+static int adi_uart4_set_brg(struct udevice *dev, int baudrate)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	struct uart4_reg *regs = plat->regs;
+	u32 divisor, uart_base_clk_rate;
+	struct clk uart_base_clk;
+
+	if (clk_get_by_index(dev, 0, &uart_base_clk)) {
+		dev_err(dev, "Could not get UART base clock\n");
+		return -1;
+	}
+
+	uart_base_clk_rate = clk_get_rate(&uart_base_clk);
+
+	if (plat->edbo) {
+		u16 divisor16 = (uart_base_clk_rate + (baudrate / 2)) / baudrate;
+
+		divisor = divisor16 | BIT(31);
+	} else {
+		// Divisor is only 16 bits
+		divisor = 0x0000ffff & ((uart_base_clk_rate + (baudrate * 8)) / (baudrate * 16));
+	}
+
+	writel(divisor, &regs->clock);
+	return 0;
+}
+
+static int adi_uart4_pending(struct udevice *dev, bool input)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	struct uart4_reg *regs = plat->regs;
+
+	if (input)
+		return (readl(&regs->status) & DR) ? 1 : 0;
+	else
+		return (readl(&regs->status) & THRE) ? 0 : 1;
+}
+
+static int adi_uart4_getc(struct udevice *dev)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	struct uart4_reg *regs = plat->regs;
+	int uart_rbr_val;
+
+	if (!adi_uart4_pending(dev, true))
+		return -EAGAIN;
+
+	uart_rbr_val = readl(&regs->rbr);
+	writel(-1, &regs->status);
+
+	return uart_rbr_val;
+}
+
+static int adi_uart4_putc(struct udevice *dev, const char ch)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	struct uart4_reg *regs = plat->regs;
+
+	if (adi_uart4_pending(dev, false))
+		return -EAGAIN;
+
+	writel(ch, &regs->thr);
+	return 0;
+}
+
+static const struct dm_serial_ops adi_uart4_serial_ops = {
+	.setbrg = adi_uart4_set_brg,
+	.getc = adi_uart4_getc,
+	.putc = adi_uart4_putc,
+	.pending = adi_uart4_pending,
+};
+
+static int adi_uart4_of_to_plat(struct udevice *dev)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	fdt_addr_t addr;
+
+	addr = dev_read_addr(dev);
+	if (addr == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	plat->regs = (struct uart4_reg *)addr;
+	plat->edbo = dev_read_bool(dev, "adi,enable-edbo");
+
+	return 0;
+}
+
+static int adi_uart4_probe(struct udevice *dev)
+{
+	struct adi_uart4_platdata *plat = dev_get_plat(dev);
+	struct uart4_reg *regs = plat->regs;
+
+	/* always enable UART to 8-bit mode */
+	writel(UEN | UMOD_UART | WLS_8, &regs->control);
+
+	writel(-1, &regs->status);
+
+	return 0;
+}
+
+static const struct udevice_id adi_uart4_serial_ids[] = {
+	{ .compatible = "adi,uart4" },
+	{ }
+};
+
+U_BOOT_DRIVER(serial_adi_uart4) = {
+	.name = "serial_adi_uart4",
+	.id = UCLASS_SERIAL,
+	.of_match = adi_uart4_serial_ids,
+	.of_to_plat = adi_uart4_of_to_plat,
+	.plat_auto = sizeof(struct adi_uart4_platdata),
+	.probe = adi_uart4_probe,
+	.ops = &adi_uart4_serial_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};