From: Robert Jarzmik <robert.jarzmik@free.fr>
To: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>,
Vinod Koul <vinod.koul@intel.com>, Arnd Bergmann <arnd@arndb.de>,
Vasily Khoruzhick <anarsoul@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org
Subject: Re: [PATCH v2 1/2] dma: mmp_dma: add support for legacy transition
Date: Thu, 19 Feb 2015 20:53:55 +0100 [thread overview]
Message-ID: <87mw498yp8.fsf@free.fr> (raw)
In-Reply-To: <54E5BB06.6000106@zonque.org> (Daniel Mack's message of "Thu, 19 Feb 2015 11:29:26 +0100")
Daniel Mack <daniel@zonque.org> writes:
> Hi Robert,
>
> Thanks for pushing this topic :)
> One minor nit:
>
>> +int mmp_pdma_toggle_reserved_channel(int legacy_channel)
>> +{
>> + if (legacy_unavailable & (1 << legacy_channel))
>> + return -EBUSY;
>> + legacy_reserved ^= 1 << legacy_channel;
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(mmp_pdma_toggle_reserved_channel);
>
> My concern is that if pxa_request_dma() is called more than once for
> whatever reason by a legacy implementation, the toggled bit mask might
> get out of sync.
This is not possible.
The first call to pxa_request_dma() sets dma_channels[i].name to a non-NULL
value.
The second call to pxa_request_dma() cannot take the same i as
!dma_channels[i].name is not fullfilled.
> As we know exactly on the caller site what we want to achieve, let's make the
> API explicit with something like:
>
> int mmp_pdma_set_reserved_channel(int legacy_channel, bool reserved)
Even if I have no strong opinion about it, I'll let the patch as it is, unless
you really want me to add the reserved parameter, in which case I'll release a
v3.
Cheers.
--
Robert
prev parent reply other threads:[~2015-02-19 19:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-14 22:47 [PATCH RFC 0/2] Prepare smooth PXA transition to dmaengine Robert Jarzmik
2015-02-14 22:47 ` [PATCH RFC 1/2] dma: mmp_dma: add support for legacy transition Robert Jarzmik
2015-02-14 22:47 ` [PATCH RFC 2/2] ARM: pxa: transition to dmaengine phase 1 Robert Jarzmik
2015-02-16 10:28 ` Arnd Bergmann
2015-02-16 11:12 ` robert.jarzmik
2015-02-16 11:33 ` Arnd Bergmann
2015-02-16 11:37 ` Daniel Mack
2015-02-16 11:14 ` Vasily Khoruzhick
2015-02-16 11:23 ` Daniel Mack
2015-02-16 16:54 ` Robert Jarzmik
2015-02-16 17:00 ` Vasily Khoruzhick
2015-02-16 18:03 ` Robert Jarzmik
2015-02-17 20:39 ` [PATCH v2 1/2] dma: mmp_dma: add support for legacy transition Robert Jarzmik
2015-02-17 20:39 ` [PATCH v2 2/2] ARM: pxa: transition to dmaengine phase 1 Robert Jarzmik
2015-02-19 10:29 ` [PATCH v2 1/2] dma: mmp_dma: add support for legacy transition Daniel Mack
2015-02-19 19:53 ` Robert Jarzmik [this message]
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