linux-kernel - Re: [PATCH v5 1/3] dt-bindings: dmaengine: Add dmamux for CV18XX/SG200X series SoC

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Date: Tue, 26 Mar 2024 12:50:33 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Inochi Amaoto <inochiama@...look.com>, Vinod Koul <vkoul@...nel.org>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Chen Wang <unicorn_wang@...look.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>
Cc: Jisheng Zhang <jszhang@...nel.org>, Liu Gui <kenneth.liu@...hgo.com>,
 Jingbao Qiu <qiujingbao.dlmu@...il.com>, dlan@...too.org,
 dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v5 1/3] dt-bindings: dmaengine: Add dmamux for
 CV18XX/SG200X series SoC

On 26/03/2024 12:41, Inochi Amaoto wrote:
>>>
>>> The driver does use this file.
>>
>> I checked and could not find. Please point me to specific parts of the code.
>>
> 
> In cv1800_dmamux_route_allocate.
>> +	regmap_set_bits(dmamux->regmap,
>> +			DMAMUX_CH_REG(chid),
>> +			DMAMUX_CH_SET(chid, devid));
>> +
>> +	regmap_update_bits(dmamux->regmap, CV1800_SDMA_DMA_INT_MUX,
>> +			   DMAMUX_INT_CH_MASK(chid, cpuid),
>> +			   DMAMUX_INT_CH_BIT(chid, cpuid));
> 
> I think this is.

So where exactly? I don't see any define being used here.
CV1800_SDMA_DMA_INT_MUX is not in your header. DMAMUX_ is not in your
header. So what are you pointing?

I don't understand this communication. Are you mocking me here or what?
It's waste of my time.

> 
>>>
>>>>> And considering the limitation of this dmamux, maybe only devices that 
>>>>> require dma as a must can have the dma assigned. 
>>>>> Due to the fact, I think it may be a long time to wait for this header
>>>>> to be used as the binding header.
>>>>
>>>> I don't understand. You did not provide a single reason why this is a
>>>> binding. Reason is: mapping IDs between DTS and driver. Where is this
>>>> reason?
>>>>
>>>
>>> It seems like that I misunderstood something. This file provides one-one
>>> mapping between the dma device id and cpuid, which is both used in the
>>> dts and driver. For dts, it provides device id and cpu id mapping. And
>>> for driver, it is used as the directive to tell how to write the mapping
>>> register.
>>
>> So where is it? I looked for DMA_TDM0_RX - nothing. Then DMA_I2C1_RX -
>> nothing. Then any "DMA_" - also looks nothing.
>>
> 
> It is just the value writed, so I say it is just a one-one mapping.
> Maybe I misunderstand the binding meaning? Is the binding a mapping 
> between the dts and something defind in the driver (not the real 
> device)?

Binding headers contains IDs which are used by the driver and DTS code.
Hardware constants are not bindings. Register values, addresses,
whatever hardware is using is not a binding.


Best regards,
Krzysztof