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SubjectRe: [PATCH] RISC-V: Relocate the kernel relative to a DRAM base.
On Tue, 27 Apr 2021 at 14:07, Nikita Ermakov <arei@altlinux.org> wrote:
>
> Try to get the base of the DRAM from a DTB to use it as a lowest address
> in physical memory to relocate the kernel. If it is not possible to
> obtain the base from a /memory node of the DTB let's make an assumption
> that the DRAM base at the beginning of the memory.
>

Why?

> Signed-off-by: Nikita Ermakov <arei@altlinux.org>
> ---
> drivers/firmware/efi/libstub/riscv-stub.c | 39 ++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
> index 380e4e251399..1b5944276e1a 100644
> --- a/drivers/firmware/efi/libstub/riscv-stub.c
> +++ b/drivers/firmware/efi/libstub/riscv-stub.c
> @@ -46,6 +46,39 @@ static u32 get_boot_hartid_from_fdt(void)
> return fdt32_to_cpu(*prop);
> }
>
> +static unsigned long get_dram_base_from_fdt(void)
> +{
> + const void *fdt;
> + int node, len;
> + const fdt32_t *addr_cells;
> + const void *prop;
> +
> + fdt = get_efi_config_table(DEVICE_TREE_GUID);
> + if (!fdt)
> + return ULONG_MAX;
> +
> + node = fdt_path_offset(fdt, "/");
> + if (node < 0)
> + return ULONG_MAX;
> +
> + addr_cells = fdt_getprop((void *)fdt, node, "#address-cells", &len);
> + if (!addr_cells)
> + return ULONG_MAX;
> +
> + node = fdt_path_offset(fdt, "/memory");
> + if (node < 0)
> + return ULONG_MAX;
> +
> + prop = fdt_getprop((void *)fdt, node, "reg", &len);
> + if (!prop)
> + return ULONG_MAX;
> +
> + if (fdt32_to_cpu(*addr_cells) > 1)
> + return fdt64_to_cpu(*((fdt64_t *)prop));
> + else
> + return fdt32_to_cpu(*((fdt32_t *)prop));
> +}
> +
> efi_status_t check_platform_features(void)
> {
> hartid = get_boot_hartid_from_fdt();
> @@ -97,7 +130,11 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
> * lowest possible memory region as long as the address and size meets
> * the alignment constraints.
> */
> - preferred_addr = MIN_KIMG_ALIGN;
> + preferred_addr = get_dram_base_from_fdt();
> + if (preferred_addr == ULONG_MAX)
> + preferred_addr = MIN_KIMG_ALIGN;
> + else
> + preferred_addr += MIN_KIMG_ALIGN;
> status = efi_relocate_kernel(image_addr, kernel_size, *image_size,
> preferred_addr, MIN_KIMG_ALIGN, 0x0);
>
> --
> 2.29.3
>

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