[U-Boot] [PATCH] rpi: Fix device tree path on ARM64

[Stephen Warren]

On 01/09/2017 06:34 AM, Tuomas Tynkkynen wrote:
> On Thu, 5 Jan 2017 16:44:43 -0700
> Stephen Warren <swarren at wwwdotorg.org> wrote:
>
>> On 01/03/2017 03:39 AM, Tuomas Tynkkynen wrote:
>>> The directory structure of device tree files produced by the kernel's
>>> 'make dtbs_install' is different on ARM64, the RPi3 device tree file is
>>> in a 'broadcom' subdirectory there. Make the set_fdtfile function account
>>> for this so that the distro boot scripts can locate the DTB file.
>>
>> I'm not 100% sure there's an expectation/guarantee that "make
>> dtbs_install" will be used to create the DTB layout that the bootloader
>> uses, although I suppose this is a reasonable thing to do.
>>
>
> It certainly would be nice from the distro's point of view to have the same
> scripts work on both ARM and ARM64.
>
>>> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
>>
>>>  static void set_fdtfile(void)
>>
>>> -	fdtfile = model->fdtfile;
>>> +	if (IS_ENABLED(CONFIG_ARM64))
>>> +		strcat(fdtfile, "broadcom/");
>>> +	strcat(fdtfile, model->fdtfile);
>>
>> Instead of writing code for this, and in particular code that doesn't
>> check for buffer size/overflow/..., wouldn't it be better to simply edit
>> the RPi 3 entry in rpi_models_new_scheme[] to contain "broadcom/" in the
>> DTB filename string?
>>
>
> I did it this way to keep the 32-bit builds looking in the old location,
> as that's where it was planned to be added for 32-bit ARM:
>
> https://patchwork.kernel.org/patch/9148261/
>
> I did consider some preprocessor magic and compile-time string concatenation
> but this seemed a cleaner way.

I'm not convinced it's cleaner. It feels best to represent data as data, 
rather than writing code to calculate it at run-time, especially once 
all the complexity of error-checking is added in. I'd suggest:

Adding the following before the models table:

#ifdef CONFIG_ARM64
#define DTB_DIR "broadcom/"
#else
#define DTB_DIR ""
#endif

Then changing the table entries from:

         [0x8] = {
                 "3 Model B",
                 "bcm2837-rpi-3-b.dtb",

... to:

         [0x8] = {
                 "3 Model B",
                 DTB_DIR "bcm2837-rpi-3-b.dtb",