linux-kernel - Re: [PATCH v3 1/3] powerpc/512x: add LocalPlus Bus FIFO device driver

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Message-ID: <560A30DF.9050900@linux.com>
Date:	Tue, 29 Sep 2015 09:34:07 +0300
From:	Alexander Popov <alex.popov@...ux.com>
To:	Timur Tabi <timur@...i.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Anatolij Gustschin <agust@...x.de>,
	Rob Herring <robh@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	linuxppc-dev@...ts.ozlabs.org, dmaengine@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexander Popov <alex.popov@...ux.com>
Subject: Re: [PATCH v3 1/3] powerpc/512x: add LocalPlus Bus FIFO device driver

On 28.09.2015 16:18, Timur Tabi wrote:
> Alexander Popov wrote:
>> The only question I have: why calling dma_unmap_single() from within
>> a spinlock is a bad practice?
> 
> I don't know, but usually functions that allocate or free memory cannot be
> called from within a spinlock.  You need to check that.  Since the MPC5121
> is a single-core CPU, you might not notice if you're doing something wrong.

I've double-checked the code and LDD and don't see any reason to avoid
calling dma_unmap_single() from interrupt context and within spinlock.

Please correct me if I'm wrong.
Thanks.

Best regards,
Alexander
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