serial: Add serial driver for Intel MID

Add a specific serial driver for Intel MID platforms.

It has special fractional divider which can be programmed via UART_PS,
UART_MUL, and UART_DIV registers.

The UART clock is calculated as

	UART clock = XTAL * UART_MUL / UART_DIV

The baudrate is calculated as

	baud rate = UART clock / UART_PS / DLAB

Initialize fractional divider correctly for Intel Edison platform.

For backward compatibility we have to set initial DLAB value to 16
and speed to 115200 baud, where initial frequency is 29491200Hz, and
XTAL frequency is 38.4MHz.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 0900cc8acb7f681d49bce1a0e016443ee5fff51c..c0ec2ec2e4d03577fbcde4eddb6ae6a1ff374a45 100644 (file)
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -376,6 +376,15 @@ config SYS_NS16550
          be used. It can be a constant or a function to get clock, eg,
          get_serial_clock().
 
+config INTEL_MID_SERIAL
+       bool "Intel MID platform UART support"
+       depends on DM_SERIAL && OF_CONTROL
+       depends on INTEL_MID
+       select SYS_NS16550
+       help
+         Select this to enable a UART for Intel MID platforms.
+         This uses the ns16550 driver as a library.
+
 config ROCKCHIP_SERIAL
        bool "Rockchip on-chip UART support"
        depends on DM_SERIAL && SPL_OF_PLATDATA

diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 8ba15ce028e87e9d9e979440d0640cc388d35844..4382cf93297b25a4ae35044bbd1dd31e813f795c 100644 (file)
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_S5P) += serial_s5p.o
 obj-$(CONFIG_MXC_UART) += serial_mxc.o
 obj-$(CONFIG_PXA_SERIAL) += serial_pxa.o
 obj-$(CONFIG_MESON_SERIAL) += serial_meson.o
+obj-$(CONFIG_INTEL_MID_SERIAL) += serial_intel_mid.o
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_ROCKCHIP_SERIAL) += serial_rockchip.o
 endif

diff --git a/drivers/serial/serial_intel_mid.c b/drivers/serial/serial_intel_mid.c
new file mode 100644 (file)
index 0000000..777c09d
--- /dev/null
+++ b/drivers/serial/serial_intel_mid.c
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * SPDX-License-Identifier:    GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <ns16550.h>
+#include <serial.h>
+
+/*
+ * The UART clock is calculated as
+ *
+ *     UART clock = XTAL * UART_MUL / UART_DIV
+ *
+ * The baudrate is calculated as
+ *
+ *     baud rate = UART clock / UART_PS / DLAB
+ */
+#define UART_PS                0x30
+#define UART_MUL       0x34
+#define UART_DIV       0x38
+
+static void mid_writel(struct ns16550_platdata *plat, int offset, int value)
+{
+       unsigned char *addr;
+
+       offset *= 1 << plat->reg_shift;
+       addr = (unsigned char *)plat->base + offset;
+
+       writel(value, addr + plat->reg_offset);
+}
+
+static int mid_serial_probe(struct udevice *dev)
+{
+       struct ns16550_platdata *plat = dev_get_platdata(dev);
+
+       /*
+        * Initialize fractional divider correctly for Intel Edison
+        * platform.
+        *
+        * For backward compatibility we have to set initial DLAB value
+        * to 16 and speed to 115200 baud, where initial frequency is
+        * 29491200Hz, and XTAL frequency is 38.4MHz.
+        */
+       mid_writel(plat, UART_MUL, 96);
+       mid_writel(plat, UART_DIV, 125);
+       mid_writel(plat, UART_PS, 16);
+
+       return ns16550_serial_probe(dev);
+}
+
+static const struct udevice_id mid_serial_ids[] = {
+       { .compatible = "intel,mid-uart" },
+       {}
+};
+
+U_BOOT_DRIVER(serial_intel_mid) = {
+       .name   = "serial_intel_mid",
+       .id     = UCLASS_SERIAL,
+       .of_match = mid_serial_ids,
+       .ofdata_to_platdata = ns16550_serial_ofdata_to_platdata,
+       .platdata_auto_alloc_size = sizeof(struct ns16550_platdata),
+       .priv_auto_alloc_size = sizeof(struct NS16550),
+       .probe  = mid_serial_probe,
+       .ops    = &ns16550_serial_ops,
+       .flags  = DM_FLAG_PRE_RELOC,
+};