firmware: google memconsole: Move specific EBDA parts

This patch splits memconsole.c in 2 parts. One containing the
architecture-independent part and the other one containing the EBDA
specific part. This prepares the integration of coreboot support for the
memconsole.

The memconsole driver is now named as memconsole-x86-legacy.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/google/memconsole-x86-legacy.c

@@ -0,0 +1,154 @@
+/*
+ * memconsole-x86-legacy.c
+ *
+ * EBDA specific parts of the memory based BIOS console.
+ *
+ * Copyright 2017 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2.0 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/dmi.h>
+#include <linux/mm.h>
+#include <asm/bios_ebda.h>
+#include <asm/e820.h>
+#include <linux/acpi.h>
+
+#include "memconsole.h"
+
+#define BIOS_MEMCONSOLE_V1_MAGIC	0xDEADBABE
+#define BIOS_MEMCONSOLE_V2_MAGIC	(('M')|('C'<<8)|('O'<<16)|('N'<<24))
+
+struct biosmemcon_ebda {
+	u32 signature;
+	union {
+		struct {
+			u8  enabled;
+			u32 buffer_addr;
+			u16 start;
+			u16 end;
+			u16 num_chars;
+			u8  wrapped;
+		} __packed v1;
+		struct {
+			u32 buffer_addr;
+			/* Misdocumented as number of pages! */
+			u16 num_bytes;
+			u16 start;
+			u16 end;
+		} __packed v2;
+	};
+} __packed;
+
+static void found_v1_header(struct biosmemcon_ebda *hdr)
+{
+	pr_info("memconsole: BIOS console v1 EBDA structure found at %p\n",
+		hdr);
+	pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num = %d\n",
+		hdr->v1.buffer_addr, hdr->v1.start,
+		hdr->v1.end, hdr->v1.num_chars);
+
+	memconsole_setup(phys_to_virt(hdr->v1.buffer_addr), hdr->v1.num_chars);
+}
+
+static void found_v2_header(struct biosmemcon_ebda *hdr)
+{
+	pr_info("memconsole: BIOS console v2 EBDA structure found at %p\n",
+		hdr);
+	pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num_bytes = %d\n",
+		hdr->v2.buffer_addr, hdr->v2.start,
+		hdr->v2.end, hdr->v2.num_bytes);
+
+	memconsole_setup(phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start),
+			 hdr->v2.end - hdr->v2.start);
+}
+
+/*
+ * Search through the EBDA for the BIOS Memory Console, and
+ * set the global variables to point to it.  Return true if found.
+ */
+static bool memconsole_ebda_init(void)
+{
+	unsigned int address;
+	size_t length, cur;
+
+	address = get_bios_ebda();
+	if (!address) {
+		pr_info("memconsole: BIOS EBDA non-existent.\n");
+		return false;
+	}
+
+	/* EBDA length is byte 0 of EBDA (in KB) */
+	length = *(u8 *)phys_to_virt(address);
+	length <<= 10; /* convert to bytes */
+
+	/*
+	 * Search through EBDA for BIOS memory console structure
+	 * note: signature is not necessarily dword-aligned
+	 */
+	for (cur = 0; cur < length; cur++) {
+		struct biosmemcon_ebda *hdr = phys_to_virt(address + cur);
+
+		/* memconsole v1 */
+		if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) {
+			found_v1_header(hdr);
+			return true;
+		}
+
+		/* memconsole v2 */
+		if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) {
+			found_v2_header(hdr);
+			return true;
+		}
+	}
+
+	pr_info("memconsole: BIOS console EBDA structure not found!\n");
+	return false;
+}
+
+static struct dmi_system_id memconsole_dmi_table[] __initdata = {
+	{
+		.ident = "Google Board",
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
+		},
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
+
+static bool __init memconsole_find(void)
+{
+	if (!dmi_check_system(memconsole_dmi_table))
+		return false;
+
+	return memconsole_ebda_init();
+}
+
+static int __init memconsole_x86_init(void)
+{
+	if (!memconsole_find())
+		return -ENODEV;
+
+	return memconsole_sysfs_init();
+}
+
+static void __exit memconsole_x86_exit(void)
+{
+	memconsole_exit();
+}
+
+module_init(memconsole_x86_init);
+module_exit(memconsole_x86_exit);
+
+MODULE_AUTHOR("Google, Inc.");
+MODULE_LICENSE("GPL");