serial: Add support for Qualcomm serial port

This driver works in "new" Data Mover UART mode, so
will be compatible with modern Qualcomm chips only.

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>

doc/device-tree-bindings/serial/msm-serial.txt

@@ -0,0 +1,6 @@
+Qualcomm UART (Data Mover mode)
+
+Required properties:
+- compatible: must be "qcom,msm-uartdm-v1.4"
+- reg: start address and size of the registers
+- clock: interface clock (must accept baudrate as a frequency)

drivers/serial/Kconfig

@@ -320,4 +320,12 @@ config XILINX_UARTLITE
 	  If you have a Xilinx based board and want to use the uartlite
 	  serial ports, say Y to this option. If unsure, say N.
 
+config MSM_SERIAL
+	bool "Qualcomm on-chip UART"
+	depends on DM_SERIAL
+	help
+	  Support Data Mover UART used on Qualcomm Snapdragon SoCs.
+	  It should support all Qualcomm devices with UARTDM version 1.4,
+	  for example APQ8016 and MSM8916.
+	  Single baudrate is supported in current implementation (115200).
 endmenu

drivers/serial/Makefile

@@ -39,6 +39,7 @@ 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
+obj-$(CONFIG_MSM_SERIAL) += serial_msm.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o

drivers/serial/serial_msm.c

@@ -0,0 +1,217 @@
+/*
+ * Qualcomm UART driver
+ *
+ * (C) Copyright 2015 Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
+ *
+ * UART will work in Data Mover mode.
+ * Based on Linux driver.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <errno.h>
+#include <serial.h>
+#include <watchdog.h>
+#include <asm/io.h>
+#include <linux/compiler.h>
+
+/* Serial registers - this driver works in uartdm mode*/
+
+#define UARTDM_DMRX             0x34 /* Max RX transfer length */
+#define UARTDM_NCF_TX           0x40 /* Number of chars to TX */
+
+#define UARTDM_RXFS             0x50 /* RX channel status register */
+#define UARTDM_RXFS_BUF_SHIFT   0x7  /* Number of bytes in the packing buffer */
+#define UARTDM_RXFS_BUF_MASK    0x7
+
+#define UARTDM_SR                0xA4 /* Status register */
+#define UARTDM_SR_RX_READY       (1 << 0) /* Word is the receiver FIFO */
+#define UARTDM_SR_TX_EMPTY       (1 << 3) /* Transmitter underrun */
+#define UARTDM_SR_UART_OVERRUN   (1 << 4) /* Receive overrun */
+
+#define UARTDM_CR                         0xA8 /* Command register */
+#define UARTDM_CR_CMD_RESET_ERR           (3 << 4) /* Clear overrun error */
+#define UARTDM_CR_CMD_RESET_STALE_INT     (8 << 4) /* Clears stale irq */
+#define UARTDM_CR_CMD_RESET_TX_READY      (3 << 8) /* Clears TX Ready irq*/
+#define UARTDM_CR_CMD_FORCE_STALE         (4 << 8) /* Causes stale event */
+#define UARTDM_CR_CMD_STALE_EVENT_DISABLE (6 << 8) /* Disable stale event */
+
+#define UARTDM_IMR                0xB0 /* Interrupt mask register */
+#define UARTDM_ISR                0xB4 /* Interrupt status register */
+#define UARTDM_ISR_TX_READY       0x80 /* TX FIFO empty */
+
+#define UARTDM_TF               0x100 /* UART Transmit FIFO register */
+#define UARTDM_RF               0x140 /* UART Receive FIFO register */
+
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct msm_serial_data {
+	phys_addr_t base;
+	unsigned chars_cnt; /* number of buffered chars */
+	uint32_t chars_buf; /* buffered chars */
+};
+
+static int msm_serial_fetch(struct udevice *dev)
+{
+	struct msm_serial_data *priv = dev_get_priv(dev);
+	unsigned sr;
+
+	if (priv->chars_cnt)
+		return priv->chars_cnt;
+
+	/* Clear error in case of buffer overrun */
+	if (readl(priv->base + UARTDM_SR) & UARTDM_SR_UART_OVERRUN)
+		writel(UARTDM_CR_CMD_RESET_ERR, priv->base + UARTDM_CR);
+
+	/* We need to fetch new character */
+	sr = readl(priv->base + UARTDM_SR);
+
+	if (sr & UARTDM_SR_RX_READY) {
+		/* There are at least 4 bytes in fifo */
+		priv->chars_buf = readl(priv->base + UARTDM_RF);
+		priv->chars_cnt = 4;
+	} else {
+		/* Check if there is anything in fifo */
+		priv->chars_cnt = readl(priv->base + UARTDM_RXFS);
+		/* Extract number of characters in UART packing buffer*/
+		priv->chars_cnt = (priv->chars_cnt >>
+				   UARTDM_RXFS_BUF_SHIFT) &
+				  UARTDM_RXFS_BUF_MASK;
+		if (!priv->chars_cnt)
+			return 0;
+
+		/* There is at least one charcter, move it to fifo */
+		writel(UARTDM_CR_CMD_FORCE_STALE,
+		       priv->base + UARTDM_CR);
+
+		priv->chars_buf = readl(priv->base + UARTDM_RF);
+		writel(UARTDM_CR_CMD_RESET_STALE_INT,
+		       priv->base + UARTDM_CR);
+		writel(0x7, priv->base + UARTDM_DMRX);
+	}
+
+	return priv->chars_cnt;
+}
+
+static int msm_serial_getc(struct udevice *dev)
+{
+	struct msm_serial_data *priv = dev_get_priv(dev);
+	char c;
+
+	if (!msm_serial_fetch(dev))
+		return -EAGAIN;
+
+	c = priv->chars_buf & 0xFF;
+	priv->chars_buf >>= 8;
+	priv->chars_cnt--;
+
+	return c;
+}
+
+static int msm_serial_putc(struct udevice *dev, const char ch)
+{
+	struct msm_serial_data *priv = dev_get_priv(dev);
+
+	if (!(readl(priv->base + UARTDM_SR) & UARTDM_SR_TX_EMPTY) &&
+	    !(readl(priv->base + UARTDM_ISR) & UARTDM_ISR_TX_READY))
+		return -EAGAIN;
+
+	writel(UARTDM_CR_CMD_RESET_TX_READY, priv->base + UARTDM_CR);
+
+	writel(1, priv->base + UARTDM_NCF_TX);
+	writel(ch, priv->base + UARTDM_TF);
+
+	return 0;
+}
+
+static int msm_serial_pending(struct udevice *dev, bool input)
+{
+	if (input) {
+		if (msm_serial_fetch(dev))
+			return 1;
+	}
+
+	return 0;
+}
+
+static const struct dm_serial_ops msm_serial_ops = {
+	.putc = msm_serial_putc,
+	.pending = msm_serial_pending,
+	.getc = msm_serial_getc,
+};
+
+static int msm_uart_clk_init(struct udevice *dev)
+{
+	uint clk_rate = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+					"clock-frequency", 115200);
+	uint clkd[2]; /* clk_id and clk_no */
+	int clk_offset;
+	struct udevice *clk;
+	int ret;
+
+	ret = fdtdec_get_int_array(gd->fdt_blob, dev->of_offset, "clock", clkd,
+				   2);
+	if (ret)
+		return ret;
+
+	clk_offset = fdt_node_offset_by_phandle(gd->fdt_blob, clkd[0]);
+	if (clk_offset < 0)
+		return clk_offset;
+
+	ret = uclass_get_device_by_of_offset(UCLASS_CLK, clk_offset, &clk);
+	if (ret)
+		return ret;
+
+	ret = clk_set_periph_rate(clk, clkd[1], clk_rate);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int msm_serial_probe(struct udevice *dev)
+{
+	struct msm_serial_data *priv = dev_get_priv(dev);
+
+	msm_uart_clk_init(dev); /* Ignore return value and hope clock was
+				  properly initialized by earlier loaders */
+
+	if (readl(priv->base + UARTDM_SR) & UARTDM_SR_UART_OVERRUN)
+		writel(UARTDM_CR_CMD_RESET_ERR, priv->base + UARTDM_CR);
+
+	writel(0, priv->base + UARTDM_IMR);
+	writel(UARTDM_CR_CMD_STALE_EVENT_DISABLE, priv->base + UARTDM_CR);
+	msm_serial_fetch(dev);
+
+	return 0;
+}
+
+static int msm_serial_ofdata_to_platdata(struct udevice *dev)
+{
+	struct msm_serial_data *priv = dev_get_priv(dev);
+
+	priv->base = dev_get_addr(dev);
+	if (priv->base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct udevice_id msm_serial_ids[] = {
+	{ .compatible = "qcom,msm-uartdm-v1.4" },
+	{ }
+};
+
+U_BOOT_DRIVER(serial_msm) = {
+	.name	= "serial_msm",
+	.id	= UCLASS_SERIAL,
+	.of_match = msm_serial_ids,
+	.ofdata_to_platdata = msm_serial_ofdata_to_platdata,
+	.priv_auto_alloc_size = sizeof(struct msm_serial_data),
+	.probe = msm_serial_probe,
+	.ops	= &msm_serial_ops,
+};