Re: [PATCH 08/10] ARM: dts: exynos: use proper 'dma-channels/requests' properties

[Krzysztof Kozlowski]

On 28/04/2022 11:57, Marek Szyprowski wrote:
> On 28.04.2022 11:54, Krzysztof Kozlowski wrote:
>> On 28/04/2022 11:50, Marek Szyprowski wrote:
>>> On 27.04.2022 17:58, Krzysztof Kozlowski wrote:
>>>> pl330 DMA controller bindings documented 'dma-channels' and
>>>> 'dma-requests' properties (without leading hash sign), so fix the DTS to
>>>> match the bindings.
>>>>
>>>> Reported-by: Rob Herring <robh@xxxxxxxxxx>
>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
>>> Are those properties really needed for PL330 driver on Exynos SoCs? I've
>>> removed them and I still see the proper values read from registers and
>>> reported in the log (Exynos4210):
>>>
>>> dma-pl330 12680000.dma-controller: Loaded driver for PL330 DMAC-141330
>>> dma-pl330 12680000.dma-controller:       DBUFF-32x4bytes Num_Chans-8
>>> Num_Peri-32 Num_Events-32
>>> dma-pl330 12690000.dma-controller: Loaded driver for PL330 DMAC-141330
>>> dma-pl330 12690000.dma-controller:       DBUFF-32x4bytes Num_Chans-8
>>> Num_Peri-32 Num_Events-32
>>> dma-pl330 12850000.dma-controller: Loaded driver for PL330 DMAC-141330
>>> dma-pl330 12850000.dma-controller:       DBUFF-64x8bytes Num_Chans-8
>>> Num_Peri-1 Num_Events-32
>>>
>>> I also don't see any code that would read those properties. IMHO they
>>> should be simply removed at all, at least for the PL330 related nodes.
>> In current Linux implementation they indeed are not used. Nothing parses
>> them. However:
>> 1. They describe (hopefully correct) the hardware.
>> 2. They might be used by other implementations of pl330 driver.
>>
>> I would not remove them from existing sources, but indeed maybe there is
>> no need to add for new files.
> 
> What's the point in having dt properties duplicating data that might be 
> read from the driver registers?

Hm, indeed, there is no point in this. Since they are read from
registers, what was the idea behind in commit 42cf20980cde?

Best regards,
Krzysztof