serial: mxs: Add MXS AUART driver

Add trivial driver for the MXS AUART IP. This is the other UART IP
present in i.MX23 and i.MX28, used to drive the non-DUART ports.

Signed-off-by: Marek Vasut <marex@denx.de>

drivers/serial/Kconfig

@@ -966,6 +966,14 @@ config MSM_GENI_SERIAL
 	  Driver works in FIFO mode.
 	  Multiple baudrates supported.
 
+config MXS_AUART_SERIAL
+	bool "MXS AUART"
+	depends on DM_SERIAL
+	help
+	  Support for Freescale i.MX23 / i.MX28 AUART or Application UART IP.
+	  This IP is present in the aforementioned SoCs, however this is not
+	  the IP used to drive the Debug UART port, for that see PL01X_SERIAL .
+
 config OCTEON_SERIAL_BOOTCMD
 	bool "MIPS Octeon PCI remote bootcmd input"
 	depends on ARCH_OCTEON

drivers/serial/Makefile

@@ -46,6 +46,7 @@ obj-$(CONFIG_BCM283X_MU_SERIAL) += serial_bcm283x_mu.o
 obj-$(CONFIG_BCM283X_PL011_SERIAL) += serial_bcm283x_pl011.o
 obj-$(CONFIG_MSM_SERIAL) += serial_msm.o
 obj-$(CONFIG_MSM_GENI_SERIAL) += serial_msm_geni.o
+obj-$(CONFIG_MXS_AUART_SERIAL) += serial_mxs.o
 obj-$(CONFIG_MVEBU_A3700_UART) += serial_mvebu_a3700.o
 obj-$(CONFIG_MPC8XX_CONS) += serial_mpc8xx.o
 obj-$(CONFIG_NULLDEV_SERIAL) += serial_nulldev.o

drivers/serial/serial_mxs.c

@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2023 Marek Vasut <marex@denx.de>
+ */
+#include <common.h>
+#include <dm.h>
+#include <malloc.h>
+#include <serial.h>
+#include <wait_bit.h>
+
+#define SET_REG					0x4
+#define CLR_REG					0x8
+
+#define AUART_CTRL0				0x00
+#define AUART_CTRL1				0x10
+#define AUART_CTRL2				0x20
+#define AUART_LINECTRL				0x30
+#define AUART_INTR				0x50
+#define AUART_DATA				0x60
+#define AUART_STAT				0x70
+
+#define AUART_CTRL0_SFTRST			BIT(31)
+#define AUART_CTRL0_CLKGATE			BIT(30)
+
+#define AUART_CTRL2_UARTEN			BIT(0)
+
+#define AUART_LINECTRL_BAUD_DIVINT(v)		(((v) & 0xffff) << 16)
+#define AUART_LINECTRL_BAUD_DIVFRAC(v)		(((v) & 0x3f) << 8)
+#define AUART_LINECTRL_WLEN(v)			((((v) - 5) & 0x3) << 5)
+
+#define AUART_STAT_TXFE				BIT(27)
+#define AUART_STAT_TXFF				BIT(25)
+#define AUART_STAT_RXFE				BIT(24)
+
+#define AUART_CLK				24000000
+
+struct mxs_auart_uart_priv {
+	void __iomem *base;
+};
+
+static int mxs_auart_uart_setbrg(struct udevice *dev, int baudrate)
+{
+	struct mxs_auart_uart_priv *priv = dev_get_priv(dev);
+	u32 div;
+
+	writel(AUART_CTRL0_CLKGATE, priv->base + AUART_CTRL0 + CLR_REG);
+	writel(AUART_CTRL0_SFTRST, priv->base + AUART_CTRL0 + CLR_REG);
+
+	writel(AUART_CTRL2_UARTEN, priv->base + AUART_CTRL2 + SET_REG);
+
+	writel(0, priv->base + AUART_INTR);
+
+	div = DIV_ROUND_CLOSEST(AUART_CLK * 32, baudrate);
+
+	/* Disable FIFO, baudrate, 8N1. */
+	writel(AUART_LINECTRL_BAUD_DIVFRAC(div & 0x3F) |
+	       AUART_LINECTRL_BAUD_DIVINT(div >> 6) |
+	       AUART_LINECTRL_WLEN(8),
+	       priv->base + AUART_LINECTRL);
+
+	return 0;
+}
+
+static int mxs_auart_uart_pending(struct udevice *dev, bool input)
+{
+	struct mxs_auart_uart_priv *priv = dev_get_priv(dev);
+	u32 stat = readl(priv->base + AUART_STAT);
+
+	if (input)
+		return !(stat & AUART_STAT_RXFE);
+
+	return !!(stat & AUART_STAT_TXFE);
+}
+
+static int mxs_auart_uart_putc(struct udevice *dev, const char ch)
+{
+	struct mxs_auart_uart_priv *priv = dev_get_priv(dev);
+	u32 stat = readl(priv->base + AUART_STAT);
+
+	if (stat & AUART_STAT_TXFF)
+		return -EAGAIN;
+
+	writel(ch, priv->base + AUART_DATA);
+
+	return 0;
+}
+
+static int mxs_auart_uart_getc(struct udevice *dev)
+{
+	struct mxs_auart_uart_priv *priv = dev_get_priv(dev);
+
+	if (!mxs_auart_uart_pending(dev, true))
+		return -EAGAIN;
+
+	return readl(priv->base + AUART_DATA) & 0xff;
+}
+
+static int mxs_auart_uart_probe(struct udevice *dev)
+{
+	struct mxs_auart_uart_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_read_addr_ptr(dev);
+	if (!priv->base)
+		return -EINVAL;
+
+	return mxs_auart_uart_setbrg(dev, CONFIG_BAUDRATE);
+}
+
+static const struct dm_serial_ops mxs_auart_uart_ops = {
+	.putc		= mxs_auart_uart_putc,
+	.pending	= mxs_auart_uart_pending,
+	.getc		= mxs_auart_uart_getc,
+	.setbrg		= mxs_auart_uart_setbrg,
+};
+
+static const struct udevice_id mxs_auart_uart_ids[] = {
+	{ .compatible = "fsl,imx23-auart", },
+	{ .compatible = "fsl,imx28-auart", },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(mxs_auart_serial) = {
+	.name		= "mxs-auart",
+	.id		= UCLASS_SERIAL,
+	.of_match	= mxs_auart_uart_ids,
+	.probe		= mxs_auart_uart_probe,
+	.ops		= &mxs_auart_uart_ops,
+	.priv_auto	= sizeof(struct mxs_auart_uart_priv),
+};