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
WARNING: multiple messages have this Message-ID (diff)
From: robert.jarzmik@free.fr (Robert Jarzmik) To: linux-arm-kernel@lists.infradead.org Subject: [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
next prev parent reply other threads:[~2015-02-19 19:54 UTC|newest] Thread overview: 32+ 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 ` 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 ` Robert Jarzmik 2015-02-14 22:47 ` [PATCH RFC 2/2] ARM: pxa: transition to dmaengine phase 1 Robert Jarzmik 2015-02-14 22:47 ` Robert Jarzmik 2015-02-16 10:28 ` Arnd Bergmann 2015-02-16 10:28 ` Arnd Bergmann 2015-02-16 11:12 ` robert.jarzmik 2015-02-16 11:12 ` robert.jarzmik at free.fr 2015-02-16 11:33 ` Arnd Bergmann 2015-02-16 11:33 ` Arnd Bergmann 2015-02-16 11:37 ` Daniel Mack 2015-02-16 11:37 ` Daniel Mack 2015-02-16 11:14 ` Vasily Khoruzhick 2015-02-16 11:14 ` Vasily Khoruzhick 2015-02-16 11:23 ` Daniel Mack 2015-02-16 11:23 ` Daniel Mack 2015-02-16 16:54 ` Robert Jarzmik 2015-02-16 16:54 ` Robert Jarzmik 2015-02-16 17:00 ` Vasily Khoruzhick 2015-02-16 17:00 ` Vasily Khoruzhick 2015-02-16 18:03 ` Robert Jarzmik 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 ` Robert Jarzmik 2015-02-17 20:39 ` [PATCH v2 2/2] ARM: pxa: transition to dmaengine phase 1 Robert Jarzmik 2015-02-17 20:39 ` Robert Jarzmik 2015-02-19 10:29 ` [PATCH v2 1/2] dma: mmp_dma: add support for legacy transition Daniel Mack 2015-02-19 10:29 ` Daniel Mack 2015-02-19 19:53 ` Robert Jarzmik [this message] 2015-02-19 19:53 ` Robert Jarzmik
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