[PATCH 1/4] fdt: add support for adding pmem nodes

[Ilias Apalodimas]

Thanks Sughosh

+CC Anton who tested that

On Fri, 25 Oct 2024 at 14:14, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> From: Masahisa Kojima <kojima.masahisa at socionext.com>
>
> One of the problems OS installers face, when running in EFI, is that
> the mounted ISO after calling ExitBootServices goes away. For some
> distros this is a problem since they rely on finding some core packages
> before continuing the installation. Distros have works around this --
> e.g Fedora has a special kernel command line parameter called
> inst.stage2 [0].
>
> ACPI has NFIT and NVDIMM support to provide ramdisks to the OS, but we
> don't have anything in place for DTs. Linux and device trees have support
> for persistent memory devices. So add a function that can inject a pmem
> node in a DT, so we can use it when launhing OS installers with EFI.
>
> [0]
> https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/installation_guide/chap-anaconda-boot-options#sect-boot-options-installer
>
> Signed-off-by: Masahisa Kojima <kojima.masahisa at socionext.com>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
>  boot/fdt_support.c    | 41 +++++++++++++++++++++++++++++++++++++++--
>  include/fdt_support.h | 13 +++++++++++++
>  2 files changed, 52 insertions(+), 2 deletions(-)
>
> diff --git a/boot/fdt_support.c b/boot/fdt_support.c
> index 2392027d40..61f725389b 100644
> --- a/boot/fdt_support.c
> +++ b/boot/fdt_support.c
> @@ -18,6 +18,7 @@
>  #include <dm/ofnode.h>
>  #include <linux/ctype.h>
>  #include <linux/types.h>
> +#include <linux/sizes.h>
>  #include <asm/global_data.h>
>  #include <asm/unaligned.h>
>  #include <linux/libfdt.h>
> @@ -463,7 +464,6 @@ void do_fixup_by_compat_u32(void *fdt, const char *compat,
>         do_fixup_by_compat(fdt, compat, prop, &tmp, 4, create);
>  }
>
> -#ifdef CONFIG_ARCH_FIXUP_FDT_MEMORY
>  /*
>   * fdt_pack_reg - pack address and size array into the "reg"-suitable stream
>   */
> @@ -491,7 +491,7 @@ static int fdt_pack_reg(const void *fdt, void *buf, u64 *address, u64 *size,
>
>         return p - (char *)buf;
>  }
> -
> +#ifdef CONFIG_ARCH_FIXUP_FDT_MEMORY
>  #if CONFIG_NR_DRAM_BANKS > 4
>  #define MEMORY_BANKS_MAX CONFIG_NR_DRAM_BANKS
>  #else
> @@ -2221,3 +2221,40 @@ int fdt_valid(struct fdt_header **blobp)
>         }
>         return 1;
>  }
> +
> +int fdt_fixup_pmem_region(void *blob, ulong addr, u32 size)
> +{
> +       u64 pmem_start[2] = { 0 };
> +       u64 pmem_size[2] = { 0 };
> +       char pmem_node[32] = {0};
> +       int nodeoffset, len;
> +       int err;
> +       u8 tmp[4 * 16]; /* Up to 64-bit address + 64-bit size */
> +
> +       if (!IS_ALIGNED(addr, SZ_2M) || !IS_ALIGNED(addr + size, SZ_2M)) {
> +               printf("Start and end address needs at 2MB alignment\n");
> +               return -1;
> +       }
> +       snprintf(pmem_node, sizeof(pmem_node), "pmem@%lx", addr);
> +       nodeoffset = fdt_find_or_add_subnode(blob, 0, pmem_node);
> +       if (nodeoffset < 0)
> +               return nodeoffset;
> +
> +       err = fdt_setprop_string(blob, nodeoffset, "compatible", "pmem-region");
> +       if (err)
> +               return err;
> +       err = fdt_setprop_empty(blob, nodeoffset, "volatile");
> +       if (err)
> +               return err;
> +       pmem_start[0] = addr;
> +       pmem_size[0] = size;
> +       len = fdt_pack_reg(blob, tmp, pmem_start, pmem_size, 1);
> +       err = fdt_setprop(blob, nodeoffset, "reg", tmp, len);
> +       if (err < 0) {
> +               printf("WARNING: could not set pmem %s %s.\n", "reg",
> +                      fdt_strerror(err));
> +               return err;
> +       }
> +
> +       return 0;
> +}
> diff --git a/include/fdt_support.h b/include/fdt_support.h
> index 741e2360c2..63ece0de32 100644
> --- a/include/fdt_support.h
> +++ b/include/fdt_support.h
> @@ -473,4 +473,17 @@ void fdt_fixup_pstore(void *blob);
>   */
>  int fdt_kaslrseed(void *blob, bool overwrite);
>
> +/**
> + * fdt_fixup_pmem_region() - add a pmem node on the device tree
> + *
> + * This functions injects a pmem node to the device tree. Usually
> + * used with EFI installers to preserve installer images
> + *
> + * @blob:      device tree provided by caller
> + * @addr:      start address of the pmem node
> + * @size:      size of the memory of the pmem node
> + * Return:     0 on success or < 0 on failure
> + */
> +int fdt_fixup_pmem_region(void *blob, ulong addr, u32 size);
> +
>  #endif /* ifndef __FDT_SUPPORT_H */
> --
> 2.34.1
>