[PATCH v2] arm: mvebu: Espressobin: Set environment variable fdtfile

[Andre Heider]

On 02/10/2020 12:49, Pali Rohár wrote:
> On Saturday 26 September 2020 11:09:59 Andre Heider wrote:
>> On 25/09/2020 09:46, Pali Rohár wrote:
>>> On Friday 11 September 2020 06:35:10 Andre Heider wrote:
>> ...
>>>> +#ifdef CONFIG_BOARD_LATE_INIT
>>>> +int board_late_init(void)
>>>> +{
>>>> +	bool ddr4, emmc;
>>>> +
>>>> +	if (env_get("fdtfile"))
>>>> +		return 0;
>>>> +
>>>> +	if (!of_machine_is_compatible("globalscale,espressobin"))
>>>> +		return 0;
>>>> +
>>>> +	/* If the memory controller has been configured for DDR4, we're running on v7 */
>>>> +	ddr4 = ((readl(A3700_CH0_MC_CTRL2_REG) >> A3700_MC_CTRL2_SDRAM_TYPE_OFFS)
>>>> +		& A3700_MC_CTRL2_SDRAM_TYPE_MASK) == A3700_MC_CTRL2_SDRAM_TYPE_DDR4;
>>>> +
>>>> +	emmc = of_machine_is_compatible("globalscale,espressobin-emmc");
>>>
>>> Maybe stupid question, but are not we able to detect if eMMC is
>>> connected or not at runtime? That could simplify setup and avoid usage
>>> of additional special DTS file for eMMC in U-Boot.
>>
>> At some point I wondered about the same.
>>
>> IIRC armbian just enables it and uses one u-boot binary everywhere. A
>> non-existing chip won't get detected, so that shouldn't be a problem.
>>
>> But I think it has more to do with enabling/powering up hardware blocks,
>> which is not wanted or may even problematic.
> 
> In U-Boot such functionality may be implemented in board_fix_fdt()
> function which allows U-Boot to modify its Device tree prior using it.
> 
> You have already wrote code which is doing V5 vs V7 detection, so
> detecting eMMC is the last thing which is missing to have just one
> U-Boot DTS file and therefore only one U-Boot binary for Espressobin.

That implies setting status=okay for the emmc node, which then powers up 
that block. I don't know if that might be problematic. Can we just do that?

The emmc detection would also add some delay to the boot process.

At least it should be powered down if no emmc chip has been detected, 
but I didn't check if that happens right now.

Regards,
Andre