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

[Marek Szyprowski]

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?


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland