linux-kernel - Re: [PATCH V6 6/8] Add EFI stub for ARM

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Date:	Tue, 14 Jan 2014 13:29:17 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Roy Franz <roy.franz@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-efi@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, matt.fleming@...el.com,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Linaro Patches <patches@...aro.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Grant Likely <grant.likely@...aro.org>,
	Dave P Martin <dave.martin@....com>
Subject: Re: [PATCH V6 6/8] Add EFI stub for ARM

On Fri, Jan 10, 2014 at 10:30 AM, Roy Franz <roy.franz@...aro.org> wrote:
> This patch adds EFI stub support for the ARM Linux kernel.  The EFI stub
> operates similarly to the x86 stub: it is a shim between the EFI firmware
> and the normal zImage entry point, and sets up the environment that the
> zImage is expecting.  This includes loading the initrd (optionaly) and
> device tree from the system partition based on the kernel command line.
> The stub updates the device tree as necessary, adding entries for EFI
> runtime services. The PE/COFF "MZ" header at offset 0 results in the
> first instruction being an add that corrupts r5, which is not used by
> the zImage interface.
>
> Signed-off-by: Roy Franz <roy.franz@...aro.org>
> Acked-by: Grant Likely <grant.likely@...aro.org>
> ---

[snip]

> +       /* Look up the base of DRAM from the device tree. */
> +       fdt = (void *)fdt_addr;
> +       node = fdt_subnode_offset(fdt, 0, "memory");
> +       region = fdt_getprop(fdt, node, "reg", NULL);
> +       if (region) {
> +               dram_base = fdt64_to_cpu(region->base);

This will not work if the address is 32-bit size.

> +       } else {
> +               /* There is no way to get amount or addresses of physical
> +                * memory installed using EFI calls.  If the device tree
> +                * we read from disk doesn't have this, there is no way
> +                * for us to construct this informaion.
> +                */
> +               pr_efi_err(sys_table, "No 'memory' node in device tree.\n");
> +               goto fail_free_fdt;

The current pc can't be used to determine the DRAM base like AUTO_ZRELADDR?

Rob
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