[5/7] arm64: dts: mediatek: mt6795: Add fixed clocks for 32kHz and 26MHz XOs

Add the 32kHz and 26MHz oscillators as fixed clocks in devicetree to
provide a good initial clock spec, since this SoC features two always
on oscillators running at the aforementioned frequencies.
While at it, since the UART clock is actually referring to the 26MHz
oscillator, remove it and assign clk26m as "baud" clock for the UARTs.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 arch/arm64/boot/dts/mediatek/mt6795.dtsi | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

On 13/05/2022 19:16, AngeloGioacchino Del Regno wrote:
> Add the 32kHz and 26MHz oscillators as fixed clocks in devicetree to
> provide a good initial clock spec, since this SoC features two always

I don't understand that part with actual patch. You claim here you add
clocks, but in DTS they were already before.

Additionally, these clocks do not belong to DTSI because, AFAIU, these
are properties of boards. At least their frequencies should be moved to
the board DTS.



Best regards,
Krzysztof

Il 16/05/22 09:10, Krzysztof Kozlowski ha scritto:
> On 13/05/2022 19:16, AngeloGioacchino Del Regno wrote:
>> Add the 32kHz and 26MHz oscillators as fixed clocks in devicetree to
>> provide a good initial clock spec, since this SoC features two always
> 
> I don't understand that part with actual patch. You claim here you add
> clocks, but in DTS they were already before.
> 
> Additionally, these clocks do not belong to DTSI because, AFAIU, these
> are properties of boards. At least their frequencies should be moved to
> the board DTS.
> 
> 

I should reword the commit description to be clearer, sorry about that: I
went with "exactly what I've done", but looking at the actual diff, it is
just a rename. What my brain was ticking on here was about removing clocks
that didn't really exist (uart_clk is not a fixed clock, etc), and adding
the ones that do exist.... but then again, the result, casually, is a rename.

In any case... no, these clocks are not board-specific for two reasons:
1. AFAIK, these fixed clock outputs are from the SoC itself, not from
    external components placed on the board, and
2. Even if these were from external components, the SoC *needs* these
    ones to work and any board that doesn't have these fixed XOs simply
    wouldn't be able to work.

Cheers,
Angelo

On 16/05/2022 10:51, AngeloGioacchino Del Regno wrote:

>>
>>
> 
> I should reword the commit description to be clearer, sorry about that: I
> went with "exactly what I've done", but looking at the actual diff, it is
> just a rename. What my brain was ticking on here was about removing clocks
> that didn't really exist (uart_clk is not a fixed clock, etc), and adding
> the ones that do exist.... but then again, the result, casually, is a rename.

Yes, some better explanation would help.

> 
> In any case... no, these clocks are not board-specific for two reasons:
> 1. AFAIK, these fixed clock outputs are from the SoC itself, not from
>     external components placed on the board, and

This would be fine.

> 2. Even if these were from external components, the SoC *needs* these
>     ones to work and any board that doesn't have these fixed XOs simply
>     wouldn't be able to work.

This is common pattern and Mediatek is not different here. In all cases
these are needed by SoC and in (almost?) all cases these should be
provided by board DTS. The DTS describes here the hardware, the board
has the clock thus the board DTS should define it.


Best regards,
Krzysztof