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

[Andre Heider]

On 03/10/2020 10:50, Pali Rohár wrote:
> On Saturday 03 October 2020 09:17:35 Andre Heider wrote:
>> 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?
> 
> No. I mean to detect presence of eMMC in board_fix_fdt() and then set
> tatus=okay only if check passed.

Yes, but how do you detect the emmc then? Enabling it in u-boot's dts 
and calling mmc_init() on it would be the easy way, but open coding all 
the required parts to do that with status=disabled could get rather big 
and/or unmaintanable (I didn't check what exactly would be required)?

> 
>> 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