[U-Boot] [U-Boot, 12/13] armv7: support rk3066 early back to bootrom in start.S

[Philipp Tomsich]

On Tue, 6 Jun 2017, Paweł Jarosz wrote:

> Rockchip bootrom first reads 1KB data from nand at offset 0x10080C00 and
> executes it. Then waits for back to bootrom and loads another 32KB to sram
> which also executes. Sdram initialisation code needs to be in one of these two
> steps. Then bootloader loads another ~200KB of data at offset 0x60000000
> and jumps to it.
>
> 32KB of data is a little low for tpl + spl part and ~200KB data is to low for
> u-boot part(for example to boot from mmc you need to disable usb support.
>
> My solution to size problem is to move sdram initialisation code to tpl stage,
> move spl part to third stage(reading 200KB data) and add support for loading
> u-boot by spl from ext2/4, fat partitions.
>
> But moving sdram initialisation code to tpl increases size of tpl above 1KB
> (first boot stage). Solution to this is to add code which will be below 1KB
> offset in tpl binary and do back to bootrom at very beginning of the tpl
> execution.
>
> Adding this few lines of code here meets these conditions.
>
> Signed-off-by: Paweł Jarosz <paweljarosz3691 at gmail.com>
> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
> arch/arm/cpu/armv7/start.S | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index f06fd28..73e03d9 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -36,6 +36,19 @@
> #endif
>
> reset:
> +
> +#if defined(CONFIG_ROCKCHIP_RK3066) && defined(CONFIG_TPL_BUILD)
> +	ldr	r3, =0x10080900
> +	ldr	r0, [r3]
> +	cmp	r0, #1
> +	movne	r0, #1
> +	strne	r0, [r3]
> +	beq	out_of_bootrom
> +	bx	lr
> +out_of_bootrom:
> +	mov	r0, #0
> +	str	r0, [r3]
> +#endif

I don't like us adding device-specific code to armv7/start.S.
Can you try to handle this in the boot0 hook (device-specific) or somewhere 
else (more suitable/chip-specific)?

> 	/* Allow the board to save important registers */
> 	b	save_boot_params
> save_boot_params_ret:
>