linux-kernel - Re: [PATCH] dmaengine: pl330: set subsys

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Date:   Thu, 9 Nov 2023 09:49:22 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     "bumyong.lee" <bumyong.lee@...sung.com>,
        'Vinod Koul' <vkoul@...nel.org>,
        'Philipp Zabel' <p.zabel@...gutronix.de>
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pl330: set subsys_initcall level

On 09/11/2023 05:34, bumyong.lee wrote:
>> On 31/10/2023 04:48, Bumyong Lee wrote:
>>> module_amba_driver is macro for module_init/exit module_init is
>>> device_initcall level when it configured with built-in driver.
>>>
>>> pl330 is dmaengine driver. because slave drivers depend on dmaengine
>>> drivers, dmaengine drivers is more appropriate subsys_initcall.
>>
>> The same is true for all resource providers and we do not manually order
>> them via initcalls. Sorry, this was fine as is. Implement defer for your
>> drivers, not hack initcalls. If you upstreamed them, then it could even
>> work out of the box for you .
>>
>> Best regards,
>> Krzysztof
> 
> I agree with your opinion that the drivers using dma-engine should implement to defer probe when dma is not initialized yet in their probe function execution.

Please wrap your emails to match mailing list discussion style.

> But if dma-engine driver and slave driver is the same initcall level, then a lot of slave drivers should defer probe every time of boot.

Which and how many drivers have this problem?

> 
> I think it's better to use subsys_initcall for pl330 like other dmaengine drivers regardless of slave driver's implementation in order to reduce defer operations.

pl330 requires other resources, so manual ordering via initcalls leads
to other problems. You solve one, create others. And no analysis of
practical impact was provided in commit msg.

Best regards,
Krzysztof