MIPS: Malta: Setup RAM regions via DT

Move memory configuration to be performed via device tree for the Malta
board. This moves more Malta specific code to malta-dtshim.c, leaving
the rest of the mti-malta code a little more board-agnostic. This will
be useful to share more code between boards, with the device tree
providing the board specifics as intended.

Since we can't rely upon Malta boards running a bootloader capable of
handling devictrees & filling in the required information, a piece of
shim code (malta_dt_shim) is added to consume the (e)memsize variables
provided as part of the bootloader environment (or on the kernel command
line) then generate the DT memory node using the provided values.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: Kumar Gala <galak@codeaurora.org>
Cc: linux-kernel@vger.kernel.org
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Patchwork: https://patchwork.linux-mips.org/patch/11222/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 162 insertions, 0 deletions

diff --git a/arch/mips/mti-malta/malta-dtshim.c b/arch/mips/mti-malta/malta-dtshim.c
new file mode 100644
index 000000000000..f7133efc5843
--- /dev/null
+++ b/arch/mips/mti-malta/malta-dtshim.c
@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2015 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/libfdt.h>
+#include <linux/of_fdt.h>
+#include <linux/sizes.h>
+#include <asm/bootinfo.h>
+#include <asm/fw/fw.h>
+#include <asm/page.h>
+
+static unsigned char fdt_buf[16 << 10] __initdata;
+
+/* determined physical memory size, not overridden by command line args	 */
+extern unsigned long physical_memsize;
+
+#define MAX_MEM_ARRAY_ENTRIES 1
+
+static unsigned __init gen_fdt_mem_array(__be32 *mem_array, unsigned long size)
+{
+	unsigned long size_preio;
+	unsigned entries;
+
+	entries = 1;
+	mem_array[0] = cpu_to_be32(PHYS_OFFSET);
+	if (config_enabled(CONFIG_EVA)) {
+		/*
+		 * The current Malta EVA configuration is "special" in that it
+		 * always makes use of addresses in the upper half of the 32 bit
+		 * physical address map, which gives it a contiguous region of
+		 * DDR but limits it to 2GB.
+		 */
+		mem_array[1] = cpu_to_be32(size);
+	} else {
+		size_preio = min_t(unsigned long, size, SZ_256M);
+		mem_array[1] = cpu_to_be32(size_preio);
+	}
+
+	BUG_ON(entries > MAX_MEM_ARRAY_ENTRIES);
+	return entries;
+}
+
+static void __init append_memory(void *fdt, int root_off)
+{
+	__be32 mem_array[2 * MAX_MEM_ARRAY_ENTRIES];
+	unsigned long memsize;
+	unsigned mem_entries;
+	int i, err, mem_off;
+	char *var, param_name[10], *var_names[] = {
+		"ememsize", "memsize",
+	};
+
+	/* if a memory node already exists, leave it alone */
+	mem_off = fdt_path_offset(fdt, "/memory");
+	if (mem_off >= 0)
+		return;
+
+	/* find memory size from the bootloader environment */
+	for (i = 0; i < ARRAY_SIZE(var_names); i++) {
+		var = fw_getenv(var_names[i]);
+		if (!var)
+			continue;
+
+		err = kstrtoul(var, 0, &physical_memsize);
+		if (!err)
+			break;
+
+		pr_warn("Failed to read the '%s' env variable '%s'\n",
+			var_names[i], var);
+	}
+
+	if (!physical_memsize) {
+		pr_warn("The bootloader didn't provide memsize: defaulting to 32MB\n");
+		physical_memsize = 32 << 20;
+	}
+
+	if (config_enabled(CONFIG_CPU_BIG_ENDIAN)) {
+		/*
+		 * SOC-it swaps, or perhaps doesn't swap, when DMA'ing
+		 * the last word of physical memory.
+		 */
+		physical_memsize -= PAGE_SIZE;
+	}
+
+	/* default to using all available RAM */
+	memsize = physical_memsize;
+
+	/* allow the user to override the usable memory */
+	for (i = 0; i < ARRAY_SIZE(var_names); i++) {
+		snprintf(param_name, sizeof(param_name), "%s=", var_names[i]);
+		var = strstr(arcs_cmdline, param_name);
+		if (!var)
+			continue;
+
+		memsize = memparse(var + strlen(param_name), NULL);
+	}
+
+	/* if the user says there's more RAM than we thought, believe them */
+	physical_memsize = max_t(unsigned long, physical_memsize, memsize);
+
+	/* append memory to the DT */
+	mem_off = fdt_add_subnode(fdt, root_off, "memory");
+	if (mem_off < 0)
+		panic("Unable to add memory node to DT: %d", mem_off);
+
+	err = fdt_setprop_string(fdt, mem_off, "device_type", "memory");
+	if (err)
+		panic("Unable to set memory node device_type: %d", err);
+
+	mem_entries = gen_fdt_mem_array(mem_array, physical_memsize);
+	err = fdt_setprop(fdt, mem_off, "reg", mem_array,
+			  mem_entries * 2 * sizeof(mem_array[0]));
+	if (err)
+		panic("Unable to set memory regs property: %d", err);
+
+	mem_entries = gen_fdt_mem_array(mem_array, memsize);
+	err = fdt_setprop(fdt, mem_off, "linux,usable-memory", mem_array,
+			  mem_entries * 2 * sizeof(mem_array[0]));
+	if (err)
+		panic("Unable to set linux,usable-memory property: %d", err);
+}
+
+void __init *malta_dt_shim(void *fdt)
+{
+	int root_off, len, err;
+	const char *compat;
+
+	if (fdt_check_header(fdt))
+		panic("Corrupt DT");
+
+	err = fdt_open_into(fdt, fdt_buf, sizeof(fdt_buf));
+	if (err)
+		panic("Unable to open FDT: %d", err);
+
+	root_off = fdt_path_offset(fdt_buf, "/");
+	if (root_off < 0)
+		panic("No / node in DT");
+
+	compat = fdt_getprop(fdt_buf, root_off, "compatible", &len);
+	if (!compat)
+		panic("No root compatible property in DT: %d", len);
+
+	/* if this isn't Malta, leave the DT alone */
+	if (strncmp(compat, "mti,malta", len))
+		return fdt;
+
+	append_memory(fdt_buf, root_off);
+
+	err = fdt_pack(fdt_buf);
+	if (err)
+		panic("Unable to pack FDT: %d\n", err);
+
+	return fdt_buf;
+}