arm/dt: probe for platforms via the device tree

If a dtb is passed to the kernel then the kernel needs to iterate
through compiled-in mdescs looking for one that matches and move the
dtb data to a safe location before it gets accidentally overwritten by
the kernel.

This patch creates a new function, setup_machine_fdt() which is
analogous to the setup_machine_atags() created in the previous patch.
It does all the early setup needed to use a device tree machine
description.

v5: - Print warning with neither dtb nor atags are passed to the kernel
    - Fix bug in setting of __machine_arch_type to the selected machine,
      not just the last machine in the list.
      Reported-by: Tixy <tixy@yxit.co.uk>
    - Copy command line directly into boot_command_line instead of cmd_line
v4: - Dump some output when a matching machine_desc cannot be found
v3: - Added processing of reserved list.
    - Backed out the v2 change that copied instead of reserved the
      dtb.  dtb is reserved again and the real problem was fixed by
      using alloc_bootmem_align() for early allocation of RAM for
      unflattening the tree.
    - Moved cmd_line and initrd changes to earlier patch to make series
      bisectable.
v2: Changed to save the dtb by copying into an allocated buffer.
    - Since the dtb will very likely be passed in the first 16k of ram
      where the interrupt vectors live, memblock_reserve() is
      insufficient to protect the dtb data.

[based on work originally written by Jeremy Kerr <jeremy.kerr@canonical.com>]
Tested-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

6 files changed, 135 insertions, 4 deletions

diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
index 4764e67fb93d..946f4d778f71 100644
--- a/arch/arm/include/asm/mach/arch.h
+++ b/arch/arm/include/asm/mach/arch.h
@@ -18,6 +18,8 @@ struct machine_desc {
         unsigned int            nr;             /* architecture number  */
         const char              *name;          /* architecture name    */
         unsigned long           boot_params;    /* tagged list          */
+        const char              **dt_compat;    /* array of device tree
+                                                 * 'compatible' strings */
 
         unsigned int            nr_irqs;        /* number of IRQs */
 
diff --git a/arch/arm/include/asm/prom.h b/arch/arm/include/asm/prom.h
index 8f1037fdc08f..11b8708fc4db 100644
--- a/arch/arm/include/asm/prom.h
+++ b/arch/arm/include/asm/prom.h
@@ -21,5 +21,17 @@ static inline void irq_dispose_mapping(unsigned int virq)
         return;
 }
 
+extern struct machine_desc *setup_machine_fdt(unsigned int dt_phys);
+extern void arm_dt_memblock_reserve(void);
+
+#else /* CONFIG_OF */
+
+static inline struct machine_desc *setup_machine_fdt(unsigned int dt_phys)
+{
+        return NULL;
+}
+
+static inline void arm_dt_memblock_reserve(void) { }
+
 #endif /* CONFIG_OF */
 #endif /* ASMARM_PROM_H */
diff --git a/arch/arm/include/asm/setup.h b/arch/arm/include/asm/setup.h
index 93b4702ffa0f..ee2ad8ae07af 100644
--- a/arch/arm/include/asm/setup.h
+++ b/arch/arm/include/asm/setup.h
@@ -218,6 +218,8 @@ extern struct meminfo meminfo;
 #define bank_phys_size(bank)    (bank)->size
 
 extern int arm_add_memory(phys_addr_t start, unsigned long size);
+extern void early_print(const char *str, ...);
+extern void dump_machine_table(void);
 
 #endif  /*  __KERNEL__  */
 
diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
index 75e3df85b88c..a701e4226a6c 100644
--- a/arch/arm/kernel/devtree.c
+++ b/arch/arm/kernel/devtree.c
@@ -21,6 +21,8 @@
 
 #include <asm/setup.h>
 #include <asm/page.h>
+#include <asm/mach/arch.h>
+#include <asm/mach-types.h>
 
 void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 {
@@ -32,6 +34,102 @@ void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
         return alloc_bootmem_align(size, align);
 }
 
+void __init arm_dt_memblock_reserve(void)
+{
+        u64 *reserve_map, base, size;
+
+        if (!initial_boot_params)
+                return;
+
+        /* Reserve the dtb region */
+        memblock_reserve(virt_to_phys(initial_boot_params),
+                         be32_to_cpu(initial_boot_params->totalsize));
+
+        /*
+         * Process the reserve map.  This will probably overlap the initrd
+         * and dtb locations which are already reserved, but overlaping
+         * doesn't hurt anything
+         */
+        reserve_map = ((void*)initial_boot_params) +
+                        be32_to_cpu(initial_boot_params->off_mem_rsvmap);
+        while (1) {
+                base = be64_to_cpup(reserve_map++);
+                size = be64_to_cpup(reserve_map++);
+                if (!size)
+                        break;
+                memblock_reserve(base, size);
+        }
+}
+
+/**
+ * setup_machine_fdt - Machine setup when an dtb was passed to the kernel
+ * @dt_phys: physical address of dt blob
+ *
+ * If a dtb was passed to the kernel in r2, then use it to choose the
+ * correct machine_desc and to setup the system.
+ */
+struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
+{
+        struct boot_param_header *devtree;
+        struct machine_desc *mdesc, *mdesc_best = NULL;
+        unsigned int score, mdesc_score = ~1;
+        unsigned long dt_root;
+        const char *model;
+
+        devtree = phys_to_virt(dt_phys);
+
+        /* check device tree validity */
+        if (be32_to_cpu(devtree->magic) != OF_DT_HEADER)
+                return NULL;
+
+        /* Search the mdescs for the 'best' compatible value match */
+        initial_boot_params = devtree;
+        dt_root = of_get_flat_dt_root();
+        for_each_machine_desc(mdesc) {
+                score = of_flat_dt_match(dt_root, mdesc->dt_compat);
+                if (score > 0 && score < mdesc_score) {
+                        mdesc_best = mdesc;
+                        mdesc_score = score;
+                }
+        }
+        if (!mdesc_best) {
+                const char *prop;
+                long size;
+
+                early_print("\nError: unrecognized/unsupported "
+                            "device tree compatible list:\n[ ");
+
+                prop = of_get_flat_dt_prop(dt_root, "compatible", &size);
+                while (size > 0) {
+                        early_print("'%s' ", prop);
+                        size -= strlen(prop) + 1;
+                        prop += strlen(prop) + 1;
+                }
+                early_print("]\n\n");
+
+                dump_machine_table(); /* does not return */
+        }
+
+        model = of_get_flat_dt_prop(dt_root, "model", NULL);
+        if (!model)
+                model = of_get_flat_dt_prop(dt_root, "compatible", NULL);
+        if (!model)
+                model = "<unknown>";
+        pr_info("Machine: %s, model: %s\n", mdesc_best->name, model);
+
+        /* Retrieve various information from the /chosen node */
+        of_scan_flat_dt(early_init_dt_scan_chosen, boot_command_line);
+        /* Initialize {size,address}-cells info */
+        of_scan_flat_dt(early_init_dt_scan_root, NULL);
+        /* Setup memory, calling early_init_dt_add_memory_arch */
+        of_scan_flat_dt(early_init_dt_scan_memory, NULL);
+
+        /* Change machine number to match the mdesc we're using */
+        __machine_arch_type = mdesc_best->nr;
+
+        return mdesc_best;
+}
+
 /**
  * irq_create_of_mapping - Hook to resolve OF irq specifier into a Linux irq#
  *
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 42c2f0cedf1b..05db25ef3dd5 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -20,6 +20,7 @@
 #include <linux/screen_info.h>
 #include <linux/init.h>
 #include <linux/kexec.h>
+#include <linux/of_fdt.h>
 #include <linux/crash_dump.h>
 #include <linux/root_dev.h>
 #include <linux/cpu.h>
@@ -42,6 +43,7 @@
 #include <asm/cachetype.h>
 #include <asm/tlbflush.h>