[PATCH v2 1/4] fdt: add support for adding pmem nodes

[Sughosh Ganu]

On Wed, 4 Dec 2024 at 01:15, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Sughosh,
>
> On Tue, 3 Dec 2024 at 09:36, 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>
> > ---
> > Changes since V1: None
> >
> >  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 2392027d40b..61f725389b7 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;
>
> I believe I asked this already, but is it possible to use the ofnode
> interface, instead of adding more and more code which we need to
> migrate later?

I had spent some time understanding what exactly is happening with the
livetree code. I had responded to you earlier [1] as to why I don't
think using livetree would be a good fit for this use case.

-sughosh

[1] - https://lists.denx.de/pipermail/u-boot/2024-December/573556.html

>
> > +       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 9447a64e060..980feb27d27 100644
> > --- a/include/fdt_support.h
> > +++ b/include/fdt_support.h
> > @@ -474,4 +474,17 @@ 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
> >
>
> Regards,
> Simon