Re: [PATCH v7 00/10] Add falcon support for am62a, 62p and 62x

[Francesco Valla <francesco@valla.it>]

Hi Anshul,

On Tuesday, 3 June 2025 at 16:24:40 Anshul Dalal <anshuld@ti.com> wrote:
> This patch set adds support for falcon boot on AM62a, 62p and 62x by
> bypassing A53 SPL and U-boot.
> 
> Existing Boot flow:
> R5 SPL -> ATF -> A53 SPL -> U-Boot -> Linux Kernel
> 
> Updated flow:
> R5 SPL -> ATF -> Linux Kernel
>
> ...

I tried this series on a custom device based on AM62P. While it's working
mostly fine, I noticed that PWM0 is not working after a falcon boot from
R5F, while it was working correctly after a boot through full U-Boot.

After a bit of debugging, I noticed that the epwm_tbclk0 is marked as
disabled in hardware in debugfs's clk_summary even if enabled by software:

 $ head -n 2 /sys/kernel/debug/clk/clk_summary && cat /sys/kernel/debug/clk/clk_summary | grep pwm

                                 enable  prepare  protect                                duty  hardware                            connection
   clock                          count    count    count        rate   accuracy phase  cycle    enable   consumer                         id
 clk:86:0                            0       0        0        250000000   0          0     50000      Y   23000000.pwm                    fck                      
 epwm_tbclk2                         0       0        0        0           0          0     50000      N   deviceless                      no_connection_id         
 epwm_tbclk1                         0       0        0        0           0          0     50000      N   deviceless                      no_connection_id         
 epwm_tbclk0                         1       1        0        0           0          0     50000      N   23000000.pwm                    tbclk


Reading the associated register (0x00104130) returns in fact 0x00000000,
while writing to it has no effect (and after a write the register reads
back as 0x00000000).


Do you have any idea on the reason of this behaviour? I don't think it is
directly related to the Falcon boot implementation, but probably a side
effect of it (maybe something that was enabled by A53 SPL?).

Thank you very much for the very valuable work!


Kind regards,
Francesco