[U-Boot] [PATCHv4 3/3] ARM64: poplar: hi3798cv200: u-boot support for Poplar 96Boards

[Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>]

On 05/10/2017 06:33 PM, Rob Herring wrote:
> On Wed, May 10, 2017 at 9:49 AM, Tom Rini <trini@konsulko.com> wrote:
>> On Wed, May 10, 2017 at 11:33:35AM +0200, Jorge Ramirez wrote:
>>> On 05/10/2017 04:30 AM, Tom Rini wrote:
>>>>> hey Tom, I am not sure how to move this forward really so let me
>>>>> clarify where I think we stand:
>>>>>
>>>>> 1. The linux kernel does not need the clock property in the uart
>>>>> nodes (only u-boot does: serial_pl01x.c needs fixing).
>>>>> 2. ehci is not present in the linux kernel poplar dts yet but it
>>>>> will be eventually.
>>>>>
>>>>> with this in mind, what is blocking the acceptance of the patchset?
>>>>>
>>>>> I can do v5 using the linux kernel dts as is and creating a
>>>>> hi3798cv200-u-boot.dtsi that simply adds the nodes above (this time
>>>>> no #include required:)  )
>>>>>
>>>>> Then when ehci is added to the kernel, the ehci node can be removed
>>>> >from u-boot.dtsi
>>>>> And when uboot updates its pl01x.c serial driver,  the uart0 node
>>>>> can be removed and the u-boot.dtsi filed completely deleted.
>>>> Can you take a stab at updating the pl01x driver?  Thanks!
>>> updating pl01x is not a big deal I dont think; however this will
>>> mean requiring a platform specific clock driver to just use the
>>> pl01x - which will take me some time to get into uboot for my
>>> platform (and the same might happen to other users).
>> Ah right.  So the flip side here, is one not allowed to have the clock
>> property anymore?  Yes, it may not be used in the kernel, but has
>> someone argued that it's not part of the hardware description?
> First I've ever seen a "clock" property. We have "clocks" from the
> clock binding which is a phandle plus #clock-cells number of args. We
> also have "clock-frequency" which is just the frequency value and has
> been around forever. Why u-boot went off and did something different i
> don't know. Sigh. What I can say is a 3rd way is not going to be
> accepted.
>
> Generally, the clock binding replaces clock-frequency, but there are
> some cases where clock binding would be overkill or too complicated
> for early boot and using clock-frequency would be okay.

agreed

> But I don't
> think "I haven't written my platform clock controller driver yet" is a
> reason to use clock-frequency as generally most platforms are going to
> have to have one. Providing a stub driver that just returns a fixed
> frequency shouldn't be too hard IMO.

I also agree but please do notice that this was not quite what I was saying.
what I am saying is that writing a stub driver to only provide a single 
UART clock rate and nothing else is also an overkill (this platform has 
no need for other clocks in u-boot)

Incidentally the value that I need to retrieve is itself hard-coded in 
an array in the kernel source code and set up via 
clk_register_fixed_rate instead of using a fixed-clock node in the 
device tree.
So there is not much value that I can see in providing such a stub 
driver really...



>
> Rob