x86: slimbootloader: Add serial driver

Slim Bootloader provides serial port info thru its HOB list pointer.
All these HOBs are eligible for Slim Bootloader based board only.
- Get serial port information from the serial port info HOB
- Leverage ns16550 driver with slimbootloader specific platform data
Signed-off-by: NAiden Park <aiden.park@intel.com>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: NBin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/slimbootloader/Makefile

@@ -2,4 +2,4 @@
 #
 # Copyright (C) 2019 Intel Corporation <www.intel.com>
 
-obj-y += car.o slimbootloader.o sdram.o
+obj-y += car.o slimbootloader.o sdram.o serial.o

arch/x86/cpu/slimbootloader/serial.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Intel Corporation <www.intel.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <ns16550.h>
+#include <serial.h>
+#include <asm/arch/slimbootloader.h>
+
+/**
+ * The serial port info hob is generated by Slim Bootloader, so eligible for
+ * Slim Bootloader based boards only.
+ */
+static int slimbootloader_serial_ofdata_to_platdata(struct udevice *dev)
+{
+	const efi_guid_t guid = SBL_SERIAL_PORT_INFO_GUID;
+	struct sbl_serial_port_info *data;
+	struct ns16550_platdata *plat = dev->platdata;
+
+	if (!gd->arch.hob_list)
+		panic("hob list not found!");
+
+	data = hob_get_guid_hob_data(gd->arch.hob_list, NULL, &guid);
+	if (!data) {
+		debug("failed to get serial port information\n");
+		return -ENOENT;
+	}
+	debug("type:%d base=0x%08x baudrate=%d stride=%d clk=%d\n",
+	      data->type,
+	      data->base,
+	      data->baud,
+	      data->stride,
+	      data->clk);
+
+	/*
+	 * The data->type provides port io or mmio access type info,
+	 * but the access type will be controlled by
+	 * CONFIG_SYS_NS16550_PORT_MAPPED or CONFIG_SYS_NS16550_MEM32.
+	 *
+	 * TBD: ns16550 access type configuration in runtime.
+	 *      ex) plat->access_type = data->type
+	 */
+	plat->base = data->base;
+	/* ns16550 uses reg_shift, then covert stride to shift */
+	plat->reg_shift = data->stride >> 1;
+	plat->clock = data->clk;
+
+	return 0;
+}
+
+static const struct udevice_id slimbootloader_serial_ids[] = {
+	{ .compatible = "intel,slimbootloader-uart" },
+	{}
+};
+
+U_BOOT_DRIVER(serial_slimbootloader) = {
+	.name	= "serial_slimbootloader",
+	.id	= UCLASS_SERIAL,
+	.of_match = slimbootloader_serial_ids,
+	.ofdata_to_platdata = slimbootloader_serial_ofdata_to_platdata,
+	.platdata_auto_alloc_size = sizeof(struct ns16550_platdata),
+	.priv_auto_alloc_size = sizeof(struct NS16550),
+	.probe	= ns16550_serial_probe,
+	.ops	= &ns16550_serial_ops,
+};

arch/x86/include/asm/arch-slimbootloader/slimbootloader.h

@@ -16,6 +16,13 @@
 	EFI_GUID(0xa1ff7424, 0x7a1a, 0x478e, \
 		0xa9, 0xe4, 0x92, 0xf3, 0x57, 0xd1, 0x28, 0x32)
 
+/**
+ * A GUID to get SerialPort info hob which is provided by Slim Bootloader
+ */
+#define SBL_SERIAL_PORT_INFO_GUID \
+	EFI_GUID(0x6c6872fe, 0x56a9, 0x4403, \
+		0xbb, 0x98, 0x95, 0x8d, 0x62, 0xde, 0x87, 0xf1)
+
 /**
  * A single entry of memory map information
  *
@@ -50,4 +57,31 @@ struct sbl_memory_map_info {
 	struct sbl_memory_map_entry	entry[0];
 };
 
+/**
+ * This includes serial port info which has already been initialized in previous
+ * Slim Bootloader stage.
+ * The Slim Bootloader initializes serial port regardless of debug/release build
+ * modes, and it passes the information to a payload thru hob. So, a payload can
+ * re-use the serial information without re-initializing serial port.
+ *
+ * @rev   : revision of serial_port_info structure. currently 1.
+ * @rsvd  : padding for alignment
+ * @type  : port io: 1, mmio: 2
+ * @base  : io base address. ex) 0x3f8, 0x80001000
+ * @baud  : uart baud rate
+ * @stride: register stride in Bytes
+ * @clk   : uart frequency in Hz
+ * @rsvd1 : reserved
+ */
+struct sbl_serial_port_info {
+	u8      rev;
+	u8      rsvd[3];
+	u32     type;
+	u32     base;
+	u32     baud;
+	u32     stride;
+	u32     clk;
+	u32     rsvd1;
+};
+
 #endif /* __SLIMBOOTLOADER_ARCH_H__ */