Re: Reset on Beaglebone Black has become unreliable/broken

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 02.12.24 15:15, Konstantin Kletschke wrote:
> On Mon, Dec 02, 2024 at 01:41:26PM +0100, Ahmad Fatoum wrote:
> I thought about the PMIC handling. I see barebox does not do anything
> with it, relies on reset default and sets CPU speed to 500MHz in
> lowlevel.c:
> 
> am33xx_pll_init(MPUPLL_M_500, DDRPLL_M_400);
> 
> Which is totally reasonable, the voltage is 1,1V then in this mode after
> powerup.
> 
> u-boot seems (I am not 100% sure) to set 1,3V but goes 1000MHz, which is
> reasonable too. So there is a difference but not a fatal one.
> 
> May I kindly aask how to properly enable the LL debugging?
> 
> I do "make am335x_mlo_defconfig", disable CONFIG_MTD and set 
> 
> CONFIG_DEBUG_LL=y
> CONFIG_DEBUG_OMAP_UART=y
> CONFIG_DEBUG_AM33XX_UART=y
> CONFIG_DEBUG_OMAP_UART_PORT=0
> 
> and compile a new MLO and copy it over. Does the other part barebox.bin
> need to be handled the same?

You can enable it for barebox.bin too, but enabling it for MLO only
should work too.

> The normal serial console I use is attached to UART0, is it save to use
> UART_PORT 0 here also?

Yes, that would be my expectation.

> This starts well on cold boot, I get some additional non readable chars
> at startup, like this:
> 
> 2~�W-�,-H]
>           ���k׋�ҫ�.LWC�C�C��arebox 2024.10.0-00152-g53c99b9f550b-dirty #15 Mon Dec 2 15:07:37 CET 2024

Hmm, CONFIG_BAUDRATE is set correctly?

> On "reset" or S1 I get no output at all, like without LL debug.
> 
> I will try to move the 4 lines in lowlevel.c like you suggested...

If it doesn't work at a later place, it won't work when you move it
earlier. I have a BBB here, so I can give enabling DEBUG_LL a try
too if you get stuck.

Cheers,
Ahmad

> 
> Regards
> Konstantin
> 
> 


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