[PATCH 4/9] ARM: dts: stm32mp1: move FDCAN to PLL4_R

[Marek Vasut]

On 2/6/20 9:59 AM, Patrick DELAUNAY wrote:
> Hi Marek,

Hello Patrick

[...]

>> My problem is with the bootloader-Linux clock tree dependency. That dependency
>> should not exist or be minimized, otherwise you end up with a very poor long-term
>> experience, see above. And if you want for this platform to be successful in the
>> industrial/automotive deployments, then you want to make sure the long-term
>> experience is a good one.
> 
> With STM32MP15x SOC and RCC, very few clocks need to be fixed by bootloaders
> (in fact more or less the root clocks of the system = frequency of PLL1 to PLL4, 
> common for many device or protected  by security feature), I think it is the case for
> any platform.
> 
> All the other clocks have a initial value / source provided by bootloaders but they can 
> also be modified at runtime (by device tree assigned-clock-parents for not secure clocks
> and with SMC call to TF-A secure monitor for "secure" clock).
> 
> For ST boards, we are trying to don't modify the initial clock tree-source only to prove
> that this clock tree is functional / correct for most of case.
> 
> But for client and after first deployment, clock tree modification must be done in Linux kernel
> without any Bootloader update (and avoid all known issue for OTA).
> 
> I shared your concerns with my team and we are completely agree with you.

So, shall we expect a proper fix for the Linux kernel too ?

[...]