Re: [PATCH v4 5/6] riscv: Copy the reserved-memory nodes to final DT

[Heinrich Schuchardt]

On 3/24/20 5:16 AM, Atish Patra wrote:

The DT used by U-Boot may be different from the DT being passed to
the OS if the DT is loaded from external media such as network or
mmc. In that case, the reserved-memory node needs to be copied to
the DT passed to the OS.

The bootefi command works in the following sequence:

* copy the passed fdt of if none is passed the internal fdt
* call image_setup_libfdt() for the copy
* create memory reservations in the UEFI memory map

Cf.
fef907b2e440 ("efi_loader: create reservations after ft_board_setup")
7be64b885a36 ("cmd: bootefi: Parse reserved-memory node from DT")

image_setup_libfdt() executes among others:

* fdt_chosen()
* arch_fixup_fdt()

Please, explain why you need to copy memory reservations, if
arch_fixup_fdt() is executed inside the bootefi command:

What would be the source of memory reservation that you would otherwise
miss in the final device tree? Do you expect that the Linux device tree
would lack reservation that are generated on the fly before U-Boot?

Best regards

Heinrich

Signed-off-by: Atish Patra <atish.pa...@wdc.com>
Reviewed-by: Bin Meng <bmeng...@gmail.com>
---
  arch/riscv/lib/bootm.c | 8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c
index 87cadad5016d..8ff8db6bf533 100644
--- a/arch/riscv/lib/bootm.c
+++ b/arch/riscv/lib/bootm.c
@@ -28,8 +28,8 @@ __weak void board_quiesce_devices(void)

  int arch_fixup_fdt(void *blob)
  {
-#ifdef CONFIG_EFI_LOADER
        int err;
+#ifdef CONFIG_EFI_LOADER
        u32 size;
        int chosen_offset;

@@ -50,6 +50,12 @@ int arch_fixup_fdt(void *blob)
        /* Overwrite the boot-hartid as U-Boot is the last stage BL */
        fdt_setprop_u32(blob, chosen_offset, "boot-hartid", gd->arch.boot_hart);
  #endif
+
+       /* Copy the reserved-memory node to the DT used by OS */
+       err = riscv_fdt_copy_resv_mem_node(gd->fdt_blob, blob);
+       if (err < 0)
+               return err;
+
        return 0;
  }