linux-kernel - Re: [PATCH 1/1] dma: actions: Fix lockdep splat for owl-dma

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Date:   Wed, 29 Apr 2020 10:36:01 +0200
From:   Andreas Färber <afaerber@...e.de>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Cristian Ciocaltea <cristian.ciocaltea@...il.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-actions@...ts.infradead.org
Subject: Re: [PATCH 1/1] dma: actions: Fix lockdep splat for owl-dma

Am 28.04.20 um 20:18 schrieb Manivannan Sadhasivam:
> On Tue, Apr 28, 2020 at 09:11:15PM +0300, Cristian Ciocaltea wrote:
>> On Tue, Apr 28, 2020 at 10:19:21PM +0530, Manivannan Sadhasivam wrote:
>>> On Tue, Apr 28, 2020 at 01:56:12PM +0300, Cristian Ciocaltea wrote:
>>>> When the kernel is build with lockdep support and the owl-dma driver is
>>>> used, the following message is shown:
[...]
>>>> The required fix is to use spin_lock_init() on the pchan lock before
>>>> attempting to call any spin_lock_irqsave() in owl_dma_get_pchan().
>>>
>>> Right, this is a bug. But while looking at the code now, I feel that we don't
>>> need 'pchan->lock'. The idea was to protect 'pchan->vchan', but I think
>>> 'od->lock' is the better candidate for that since it already protects it in
>>> 'owl_dma_terminate_pchan'.
>>>
>>> So I'd be happy if you remove the lock from 'pchan' and just directly use the
>>> one in 'od'.
>>>
>>> Out of curiosity, on which platform you're testing this?
>>
>> Totally agree, I will send a new patch revision as soon as I do some
>> more testing.
> 
> Coo[l], thanks!
> 
>> I'm currently experimenting on an Actions S500 based board (Roseapple Pi)
>> trying to extend, if possible, the existing mainline support for those
>> SoCs.
> 
> Awesome! It's great to see that Actions platform is seeing some attention
> these days :)
> 
>> I don't have much progress so far, since I started quite recently
>> and I also lack experience in the kernel development area, but I do my
>> best to come back with more patches once I get a consistent functionality.
> 
> No worries. Feel free to reach out to me if you have any questions. There is
> a lot of work to do and for sure it will be a good learning curve.
> 
> We do have an IRC channel (##linux-actions) for quick discussions. Fee[l] free
> to join!

Please also CC the linux-actions mailing list on any patches:

https://lists.infradead.org/mailman/listinfo/linux-actions

Mani, do you have a 5.7-rc1 tree set up or should I queue patches this 
round? It still seems missing in MAINTAINERS, and then there's Matheus' 
patches in review.

Thanks,
Andreas

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