Re: [PATCH] ARM: /proc/cpuinfo: DT: Add support for Revision

[Rob Herring <robherring2@gmail.com>]

On Mon, Jan 26, 2015 at 1:09 PM, Pali Rohár <pali.rohar@gmail.com> wrote:
> 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.

It is the correct property, but /revision in DT is a string.

You need to add your own sign-off.

Rob