[U-Boot] [PATCH v5 4/9] board: ti: dra7xx-evm: turn on USB clocks in late init stage

[Marek Vasut]

On 05/16/2018 11:00 AM, Jean-Jacques Hiblot wrote:
> 
> 
> On 16/05/2018 00:13, Marek Vasut wrote:
>> On 05/15/2018 06:10 PM, Jean-Jacques Hiblot wrote:
>>> Hi Marek,
>>>
>>>
>>> On 04/05/2018 21:06, Marek Vasut wrote:
>>>>>>>> Shouldnt the driver turn this on?
>>>>>>> AFAIK there is no clock driver for the OMAP. So we have to do it
>>>>>>> before
>>>>>>> the driver is probed.
>>>>>> Maybe it's time to implement it instead of piling up those hacks ?
>>>>> I was thinking along the same lines at some point but then I realized
>>>>> that it will make the SPL really big. And we are already tight on some
>>>>> platforms like am335x.
>>>> But this is not only SPL , right ? And yes, for SPL you might need to
>>>> poke registers or something.
>>> IMHO having 2 different ways to enable the clocks in SPL and in u-boot
>>> is an not improvement over the current situation.
>>> In any case, This is a subject that can be discussed.
>> Do you have a better idea ?
> I would keep it as it is today.
> 
> After studying the clock management in Linux, I believe that
> implementing the clock drivers in u-boot won't be an easy task and
> moreover won't make things much cleaner.
> The way clocks are handled in Linux for the omap platforms is not
> completely standard. There are a lot of clocks that are handled by the
> clock framework (pll, mux, some gates, ...) but most of the clock gating
> for peripherals is handled the HWMOD subsystem which automatically
> enables/disables the clocks of the peripherals. Parameters for this
> subsystem are hard-coded in platform code (in
> arch/arm/mach-omap2/omap-hwmod_xxx_data.c) not in the DTS. It also
> handle clock and power domains.
> HWMOD is probably going to go away some day, I'm not sure that we want
> to implement it in u-boot. Until hwmod has completely replaced by more
> generic frameworks, I would stick to platform code to enable clocks in
> u-boot.

But if this keeps going on, eventually we will regress to where we were
years ago -- having huge platform specific list of registers to poke to
set a platform up and that'd be it ?

-- 
Best regards,
Marek Vasut