From: Dmitry Osipenko <digetx@gmail.com>
To: Vinod Koul <vkoul@kernel.org>, Jon Hunter <jonathanh@nvidia.com>
Cc: Laxman Dewangan <ldewangan@nvidia.com>,
Thierry Reding <thierry.reding@gmail.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] dmaengine: tegra-apb: Handle DMA_PREP_INTERRUPT flag properly
Date: Tue, 21 May 2019 16:46:24 +0300 [thread overview]
Message-ID: <973513f9-0d87-4c39-6b29-f98a1d9dc00c@gmail.com> (raw)
In-Reply-To: <20190521045545.GP15118@vkoul-mobl>
21.05.2019 7:55, Vinod Koul пишет:
> On 08-05-19, 10:24, Jon Hunter wrote:
>>
>> On 05/05/2019 19:12, Dmitry Osipenko wrote:
>>> The DMA_PREP_INTERRUPT flag means that descriptor's callback should be
>>> invoked upon transfer completion and that's it. For some reason driver
>>> completely disables the hardware interrupt handling, leaving channel in
>>> unusable state if transfer is issued with the flag being unset. Note
>>> that there are no occurrences in the relevant drivers that do not set
>>> the flag, hence this patch doesn't fix any actual bug and merely fixes
>>> potential problem.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>
>> >From having a look at this, I am guessing that we have never really
>> tested the case where DMA_PREP_INTERRUPT flag is not set because as you
>> mentioned it does not look like this will work at all!
>
> That is a fair argument
>>
>> Is there are use-case you are looking at where you don't set the
>> DMA_PREP_INTERRUPT flag?
>>
>> If not I am wondering if we should even bother supporting this and warn
>> if it is not set. AFAICT it does not appear to be mandatory, but maybe
>> Vinod can comment more on this.
>
> This is supposed to be used in the cases where you submit a bunch of
> descriptors and selectively dont want an interrupt in few cases...
>
> Is this such a case?
The flag is set by device drivers. AFAIK, none of the drivers that are
used on Tegra SoC's make a use of that flag, at least not in upstream.
prev parent reply other threads:[~2019-05-21 13:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-05 18:12 [PATCH v1] dmaengine: tegra-apb: Handle DMA_PREP_INTERRUPT flag properly Dmitry Osipenko
2019-05-08 9:24 ` Jon Hunter
2019-05-08 12:37 ` Dmitry Osipenko
2019-05-21 4:55 ` Vinod Koul
2019-05-21 13:46 ` Dmitry Osipenko [this message]
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