[PATCH v1 1/1] arm64: zynqmp: Fix k24 psu_init_gpl.c clocking

[Michal Simek]

Hi Neal,

On 12/14/23 18:11, Frager, Neal wrote:
> Hi Michal,
> 
>>
>>> This patch corrects the k24 som clocking configuration such that the serdes
>>
>>> Corrects the ...
>>
>> Ok.
>>
>>> clocks are correctly enabled and the usb0 is configured to use the psgtr
>>> refclk2 for usb3 mode.
>>
>>> I sort of have no problem with this patch but it should be better described.
>>> Pretty much serdes configuration should be called from u-boot because we already
>>> have psgtr driver and usb3.0 can be configured out of it.
>>> But we can't touch dwc3 driver now that's why the only way to do it is to
>>> configure via psu_init.
>>> But it should be clear from commit message that it is workaround not really
>>> something what should be here.
>>
>> I will re-test this without the serdes additions to see if they are
>> really necessary.
>>
>>> This patch also corrects the configuration of mio pins mio76 and mio77
>>> which should be configured as gpio pins.
>>
>>> This is definitely fine.
>>
>> Good.
>>
>>>
>>> Signed-off-by: Neal Frager <neal.frager at amd.com>
>>
>>> You mentioned that SPL didn't work before. Is it because of incorrect serdes
>>> configuration? Because that's sounds weird because you don't need serdes
>>> initialization for booting out of qspi. That's why looking for which is that bit
>>> which make SPL work on KD240.
>>
>> The SPL works.  The issue is the same as I had with the kr260
>> board.  The sd card interface is over usb, so unless the usb3
>> works correctly, u-boot has no sd card interface and cannot
>> find the Linux kernel and file system.
>>
>> So what I meant was that I cannot boot up properly
>> when starting from the SPL.  This is what this patch is
>> meant to fix.
> 
>> What I have seen on KD240 was that I could get to u-boot prompt. And for that
>> you don't need any serdes initialization at all.
> 
> Yes, agreed.  I can get to u-boot prompt too without
> any additional patches.

ok. Good.

> 
>> For booting OS you need it if you want to use USB3.0.
> 
> And for the kd240, sd card requires usb3.0 also.
> 
>> That's why I want to make it clear what makes kd240 to boot u-boot.
>> And what makes to access sd over usb to boot OS.
> 
> Understood.  The issue I am trying to solve is enabling
> sd over usb to boot OS.

good.

> 
>> And no issue to add serdes initialization to psu_init to get boot OS part to
>> work till someone has time to wire psgtr driver with dwc3 to configure it at run
>> time.
> 
> Is someone currently working on wiring psgtr driver with dwc3?

I don't think so.

> 
> If this were to happen soon, than this psu_init_gpl.c patch
> would become unnecessary.

I will take some time to get there that's why it is fine to enable serdes lines 
via psu_init. You can put k24 to kv260/kr260 carrier cards but that's not normal 
mode of operations that's why it shouldn't be a problem.
Maybe it is nice to test it to see but definitely not requirement.

Thanks,
Michal