[PATCH v2 3/3] renesas: rcar3: Load the correct device tree

[Marek Vasut]

On 6/14/23 17:10, Detlev Casanova wrote:
> On Wednesday, June 14, 2023 9:53:14 A.M. EDT Marek Vasut wrote:
>> On 6/12/23 21:51, Detlev Casanova wrote:
>>> The Renesas R-Car Gen3 boards use different device trees than
>>> the default one.
>>>
>>> This commit uses the sysinfo's board id and revision
>>>
>>> to determine which linux device tree to load:
>>>    * H3 (Starter Kit Premier v2.0): renesas/r8a77951-ulcb.dtb
>>>    * H3e (Starter Kit Premier v2.1): renesas/r8a779m1-ulcb.dtb
>>
>> This is not about loading DTs (as the subject would suggest), this is
>> about setting the correct default DT name in environment.
>>
>>> Signed-off-by: Detlev Casanova <detlev.casanova at collabora.com>
>>> ---
>>>
>>>    board/renesas/ulcb/ulcb.c    | 59 ++++++++++++++++++++++++++++++++++++
>>>    configs/rcar3_ulcb_defconfig |  1 +
>>>    2 files changed, 60 insertions(+)
>>>
>>> diff --git a/board/renesas/ulcb/ulcb.c b/board/renesas/ulcb/ulcb.c
>>> index 1477750f921..cc78e0952b6 100644
>>> --- a/board/renesas/ulcb/ulcb.c
>>> +++ b/board/renesas/ulcb/ulcb.c
>>> @@ -27,6 +27,7 @@
>>>
>>>    #include <asm/arch/sh_sdhi.h>
>>>    #include <i2c.h>
>>>    #include <mmc.h>
>>>
>>> +#include <sysinfo.h>
>>>
>>>    DECLARE_GLOBAL_DATA_PTR;
>>>
>>> @@ -65,6 +66,64 @@ int board_init(void)
>>>
>>>    	return 0;
>>>    
>>>    }
>>>
>>> +int misc_init_r(void)
>>> +{
>>> +	struct udevice *dev;
>>> +	int board_id;
>>> +	int rev_major, rev_minor;
>>> +	int ret = sysinfo_get(&dev);
>>> +
>>> +	if (ret) {
>>> +		debug("Cannot get sysinfo: %d\n", ret);
>>> +		return 0;
>>
>> Why do we ignore errors here ?
>>
>>> +	}
>>> +
>>> +	ret = sysinfo_detect(dev);
>>> +	if (ret) {
>>> +		debug("Cannot detect sysinfo: %d\n", ret);
>>> +		return 0;
>>> +	}
>>
>> Looking at all this, I really have to wonder, wouldn't it be nicer to
>> introduce a 'sysinfo' command which provides interface to obtain the
>> different properties (like board name, id, revision ...) from U-Boot
>> command line, and then script the DT selection in U-Boot shell ?
> 
> Yes, that could be a good option. This is more based on how raspberry pis are
> selecting the correct devicetree in `board/raspberrypi/rpi/rpi.c`.
> It is either about having simple shell scripts that are similar between
> devices and the implementation is "hidden" in C for each platform (maybe
> easier to use but less flexible). Or more complex shell scripts with simpler C
> implementation (more flexible but having to modify a boot script can become
> complicated for users)
> 
> Has this direction choice been discussed in the past already ?

The less hard-coded board code (which cannot be updated by the user 
easily), the better. Scripts can be updated in deployment far easier 
than the bootloader itself. Hence the push for scripts over custom C code.