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    Subject[PATCH] ARM: /proc/cpuinfo: DT: Add support for Revision
    Date
    Ok, here is patch which set Revision field (global variable system_rev) in /proc/cpuinfo from DT 
    revision property:

    diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
    index 11c54de..9946c1b 100644
    --- a/arch/arm/kernel/devtree.c
    +++ b/arch/arm/kernel/devtree.c
    @@ -19,6 +19,7 @@
    #include <linux/of_irq.h>
    #include <linux/of_platform.h>
    #include <linux/smp.h>
    +#include <linux/libfdt_env.h>

    #include <asm/cputype.h>
    #include <asm/setup.h>
    @@ -26,6 +27,7 @@
    #include <asm/smp_plat.h>
    #include <asm/mach/arch.h>
    #include <asm/mach-types.h>
    +#include <asm/system_info.h>


    #ifdef CONFIG_SMP
    @@ -204,6 +206,8 @@ static const void * __init arch_get_next_mach(const char *const **match)
    const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
    {
    const struct machine_desc *mdesc, *mdesc_best = NULL;
    + unsigned long dt_root;
    + const u32 *prop;

    #ifdef CONFIG_ARCH_MULTIPLATFORM
    DT_MACHINE_START(GENERIC_DT, "Generic DT based system")
    @@ -215,17 +219,16 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
    if (!dt_phys || !early_init_dt_verify(phys_to_virt(dt_phys)))
    return NULL;

    + dt_root = of_get_flat_dt_root();
    mdesc = of_flat_dt_match_machine(mdesc_best, arch_get_next_mach);

    if (!mdesc) {
    const char *prop;
    int size;
    - unsigned long dt_root;

    early_print("\nError: unrecognized/unsupported "
    "device tree compatible list:\n[ ");

    - dt_root = of_get_flat_dt_root();
    prop = of_get_flat_dt_prop(dt_root, "compatible", &size);
    while (size > 0) {
    early_print("'%s' ", prop);
    @@ -246,5 +249,10 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
    /* Change machine number to match the mdesc we're using */
    __machine_arch_type = mdesc->nr;

    + /* Set system revision from DT */
    + prop = of_get_flat_dt_prop(dt_root, "revision", NULL);
    + if (prop)
    + system_rev = fdt32_to_cpu(*prop);
    +
    return mdesc;
    }

    And here is patch which convert ATAG revision into DT revision property and append it into DT in
    decompress code:

    diff --git a/arch/arm/boot/compressed/atags_to_fdt.c b/arch/arm/boot/compressed/atags_to_fdt.c
    index 9448aa0..e7e1cc9 100644
    --- a/arch/arm/boot/compressed/atags_to_fdt.c
    +++ b/arch/arm/boot/compressed/atags_to_fdt.c
    @@ -171,6 +171,8 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
    cpu_to_fdt32(atag->u.mem.size);
    }

    + } else if (atag->hdr.tag == ATAG_REVISION) {
    + setprop_cell(fdt, "/", "revision", atag->u.revision.rev);
    } else if (atag->hdr.tag == ATAG_INITRD2) {
    uint32_t initrd_start, initrd_size;
    initrd_start = atag->u.initrd.start;

    I tested it on DT booted Nokia N900 and it is working, in /proc/cpuinfo is revision from ATAG.

    I do not know which DT property to use for storing HW Revision, so if "/revision" is not correct one,
    let me know what to use instead. Also you can add my Signed-off-by for both patches.

    --
    Pali Rohár
    pali.rohar@gmail.com
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