linux-kernel - Re: [PATCH v2] dmaengine: axi-dmac: Request IRQ with IRQF

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Date:   Fri, 27 Apr 2018 17:18:29 +0200
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Moritz Fischer <moritz.fischer.private@...il.com>,
        Vinod Koul <vinod.koul@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dmaengine@...r.kernel.org, dan.j.williams@...el.com
Subject: Re: [PATCH v2] dmaengine: axi-dmac: Request IRQ with IRQF_SHARED

On 04/27/2018 05:15 PM, Moritz Fischer wrote:
> Hi Vinod,
> 
> On Fri, Apr 27, 2018 at 12:08 AM, Vinod Koul <vinod.koul@...el.com> wrote:
>> On Fri, Apr 27, 2018 at 08:53:39AM +0200, Lars-Peter Clausen wrote:
>>> On 04/27/2018 07:11 AM, Vinod Koul wrote:
>>>> On Thu, Apr 26, 2018 at 10:40:00AM -0700, Moritz Fischer wrote:
>>>>> Request IRQ with IRQF_SHARED flag. This works since the interrupt
>>>>> handler already checks if there is an actual IRQ pending and returns
>>>>> IRQ_NONE otherwise.
>>>>
>>>> hmmm what are we trying to fix here? Is your device on a shared line or not?
>>>
>>> IRQF_SHARED does not mean that the IRQ is on a shared line. It means that
>>> the driver can handle it if the IRQ is on a shared line. Since the driver
>>> can handle it setting the flag is a good idea since this enables usecases
>>> where the line is shared.
>>
>> Yes that is correct indeed, but what is the motivation for the change.
>>
>> If you never expect this to be in shared environment why to do this?
>> Sorry but "it works" is not a good enough reason for this change, to enable
>> usecases where the line is shared is a good reason :)
> 
> Remember, this is an FPGA soft core. I happen to have a design [1] where it
> is hooked up with multiple of them on one IRQ line, so to make this work,
> I need this change.

I think what Vinod is asking for is a change to the commit message saying
that "this change enables the driver to be used with devices where the
interrupt line is shared".