serial: add BCM283x mini UART driver

The RPi3 typically uses the regular UART for high-speed communication with
the Bluetooth device, leaving us the mini UART to use for the serial
console. Add support for this UART so we can use it.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

drivers/serial/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_UNIPHIER_SERIAL) += serial_uniphier.o
 obj-$(CONFIG_STM32_SERIAL) += serial_stm32.o
 obj-$(CONFIG_PIC32_SERIAL) += serial_pic32.o
 obj-$(CONFIG_STM32X7_SERIAL) += serial_stm32x7.o
+obj-$(CONFIG_BCM283X_MU_SERIAL) += serial_bcm283x_mu.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o

drivers/serial/serial_bcm283x_mu.c

@@ -0,0 +1,140 @@
+/*
+ * (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
+ *
+ * Derived from pl01x code:
+ *
+ * (C) Copyright 2000
+ * Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
+ *
+ * (C) Copyright 2004
+ * ARM Ltd.
+ * Philippe Robin, <philippe.robin@arm.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/* Simple U-Boot driver for the BCM283x mini UART */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <watchdog.h>
+#include <asm/io.h>
+#include <serial.h>
+#include <dm/platform_data/serial_bcm283x_mu.h>
+#include <linux/compiler.h>
+#include <fdtdec.h>
+
+struct bcm283x_mu_regs {
+	u32 io;
+	u32 iir;
+	u32 ier;
+	u32 lcr;
+	u32 mcr;
+	u32 lsr;
+	u32 msr;
+	u32 scratch;
+	u32 cntl;
+	u32 stat;
+	u32 baud;
+};
+
+#define BCM283X_MU_LCR_DATA_SIZE_8	3
+
+#define BCM283X_MU_LSR_TX_IDLE		BIT(6)
+/* This actually means not full, but is named not empty in the docs */
+#define BCM283X_MU_LSR_TX_EMPTY		BIT(5)
+#define BCM283X_MU_LSR_RX_READY		BIT(0)
+
+struct bcm283x_mu_priv {
+	struct bcm283x_mu_regs *regs;
+};
+
+static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
+{
+	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
+	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
+	struct bcm283x_mu_regs *regs = priv->regs;
+	u32 divider;
+
+	if (plat->skip_init)
+		return 0;
+
+	divider = plat->clock / (baudrate * 8);
+
+	writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
+	writel(divider - 1, &regs->baud);
+
+	return 0;
+}
+
+static int bcm283x_mu_serial_probe(struct udevice *dev)
+{
+	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
+	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
+
+	priv->regs = (struct bcm283x_mu_regs *)plat->base;
+
+	return 0;
+}
+
+static int bcm283x_mu_serial_getc(struct udevice *dev)
+{
+	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
+	struct bcm283x_mu_regs *regs = priv->regs;
+	u32 data;
+
+	/* Wait until there is data in the FIFO */
+	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
+		return -EAGAIN;
+
+	data = readl(&regs->io);
+
+	return (int)data;
+}
+
+static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
+{
+	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
+	struct bcm283x_mu_regs *regs = priv->regs;
+
+	/* Wait until there is space in the FIFO */
+	if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
+		return -EAGAIN;
+
+	/* Send the character */
+	writel(data, &regs->io);
+
+	return 0;
+}
+
+static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
+{
+	struct bcm283x_mu_priv *priv = dev_get_priv(dev);
+	struct bcm283x_mu_regs *regs = priv->regs;
+	unsigned int lsr = readl(&regs->lsr);
+
+	if (input) {
+		WATCHDOG_RESET();
+		return lsr & BCM283X_MU_LSR_RX_READY;
+	} else {
+		return !(lsr & BCM283X_MU_LSR_TX_IDLE);
+	}
+}
+
+static const struct dm_serial_ops bcm283x_mu_serial_ops = {
+	.putc = bcm283x_mu_serial_putc,
+	.pending = bcm283x_mu_serial_pending,
+	.getc = bcm283x_mu_serial_getc,
+	.setbrg = bcm283x_mu_serial_setbrg,
+};
+
+U_BOOT_DRIVER(serial_bcm283x_mu) = {
+	.name = "serial_bcm283x_mu",
+	.id = UCLASS_SERIAL,
+	.platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
+	.probe = bcm283x_mu_serial_probe,
+	.ops = &bcm283x_mu_serial_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+	.priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
+};

include/dm/platform_data/serial_bcm283x_mu.h

@@ -0,0 +1,24 @@
+/*
+ * (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
+ *
+ * Derived from pl01x code:
+ * Copyright (c) 2014 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __serial_bcm283x_mu_h
+#define __serial_bcm283x_mu_h
+
+/*
+ *Information about a serial port
+ *
+ * @base: Register base address
+ */
+struct bcm283x_mu_serial_platdata {
+	unsigned long base;
+	unsigned int clock;
+	bool skip_init;
+};
+
+#endif