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    Subject[PATCH 5/8] arm/dt: probe for platforms via the device tree
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    Date
    Add a macro to define a device-tree-probable machine
    (DT_MACHINE_START/DT_MACHINE_END), and iterate through compiled-in
    mdescs once we have the DT. 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.

    [based on work originally written by Jeremy Kerr <jeremy.kerr@canonical.com>]
    Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
    ---
    arch/arm/include/asm/mach/arch.h | 2 +
    arch/arm/include/asm/prom.h | 9 ++++++
    arch/arm/include/asm/setup.h | 1 +
    arch/arm/kernel/devtree.c | 60 ++++++++++++++++++++++++++++++++++++++
    arch/arm/kernel/setup.c | 10 +++++-
    5 files changed, 80 insertions(+), 2 deletions(-)

    diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
    index 3a0893a..2ed24e7 100644
    --- a/arch/arm/include/asm/mach/arch.h
    +++ b/arch/arm/include/asm/mach/arch.h
    @@ -22,6 +22,8 @@ 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 8f1037f..b692f41 100644
    --- a/arch/arm/include/asm/prom.h
    +++ b/arch/arm/include/asm/prom.h
    @@ -21,5 +21,14 @@ static inline void irq_dispose_mapping(unsigned int virq)
    return;
    }

    +extern struct machine_desc *setup_machine_fdt(unsigned int dt_phys);
    +
    +#else /* CONFIG_OF */
    +
    +static inline struct machine_desc *setup_machine_fdt(unsigned int dt_phys)
    +{
    + return NULL;
    +}
    +
    #endif /* CONFIG_OF */
    #endif /* ASMARM_PROM_H */
    diff --git a/arch/arm/include/asm/setup.h b/arch/arm/include/asm/setup.h
    index 0809235..b46d320 100644
    --- a/arch/arm/include/asm/setup.h
    +++ b/arch/arm/include/asm/setup.h
    @@ -223,6 +223,7 @@ extern struct meminfo meminfo;

    extern void arm_reserve_devtree(unsigned long start, unsigned long size);
    extern int arm_add_memory(unsigned long start, unsigned long size);
    +extern char cmd_line[COMMAND_LINE_SIZE];

    #endif /* __KERNEL__ */

    diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
    index ac48da2..f7788be 100644
    --- a/arch/arm/kernel/devtree.c
    +++ b/arch/arm/kernel/devtree.c
    @@ -21,6 +21,7 @@

    #include <asm/setup.h>
    #include <asm/page.h>
    +#include <asm/mach/arch.h>

    void __init early_init_dt_add_memory_arch(u64 base, u64 size)
    {
    @@ -45,3 +46,62 @@ unsigned int irq_create_of_mapping(struct device_node *controller,
    return intspec[0];
    }
    EXPORT_SYMBOL_GPL(irq_create_of_mapping);
    +
    +extern struct machine_desc __arch_info_begin, __arch_info_end;
    +
    +/**
    + * 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 (mdesc = &__arch_info_begin; mdesc < &__arch_info_end; 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) {
    + printk("Machine not supported, unable to continue.\n");
    + while (1);
    + }
    +
    + 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);
    +
    + arm_reserve_devtree(dt_phys, be32_to_cpu(devtree->totalsize));
    +
    + /* Retrieve various information from the /chosen node */
    + of_scan_flat_dt(early_init_dt_scan_chosen, NULL);
    + /* 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);
    + /* Save command line for /proc/cmdline */
    + strlcpy(boot_command_line, cmd_line, COMMAND_LINE_SIZE);
    +
    + return mdesc_best;
    +}
    diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
    index cbc1836..3db0cbb 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>

    +#include <asm/prom.h>
    #include <asm/mach/arch.h>
    #include <asm/mach/irq.h>
    #include <asm/mach/time.h>
    @@ -125,7 +127,7 @@ EXPORT_SYMBOL(elf_platform);

    static const char *cpu_name;
    static const char *machine_name;
    -static char __initdata cmd_line[COMMAND_LINE_SIZE];
    +char cmd_line[COMMAND_LINE_SIZE];
    struct machine_desc *machine_desc __initdata;

    static char default_command_line[COMMAND_LINE_SIZE] __initdata = CONFIG_CMDLINE;
    @@ -838,7 +840,9 @@ void __init setup_arch(char **cmdline_p)
    unwind_init();

    setup_processor();
    - mdesc = setup_machine_tags(machine_arch_type);
    + mdesc = setup_machine_fdt(__atags_pointer);
    + if (!mdesc)
    + mdesc = setup_machine_tags(machine_arch_type);
    machine_desc = mdesc;
    machine_name = mdesc->name;

    @@ -859,6 +863,8 @@ void __init setup_arch(char **cmdline_p)
    paging_init(mdesc);
    request_standard_resources(mdesc);

    + unflatten_device_tree();
    +
    #ifdef CONFIG_SMP
    if (is_smp())
    smp_init_cpus();


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