linux-kernel - Re: [PATCH v2] spi: qup: Add DMA capabilities

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 24 Feb 2015 16:38:40 -0600
From:	Andy Gross <agross@...eaurora.org>
To:	Stanimir Varbanov <stanimir.varbanov@...aro.org>
Cc:	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-spi@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Kumar Gala <galak@...eaurora.org>,
	Sagar Dharia <sdharia@...eaurora.org>,
	Daniel Sneddon <dsneddon@...eaurora.org>
Subject: Re: [PATCH v2] spi: qup: Add DMA capabilities

On Tue, Feb 24, 2015 at 06:08:54PM +0200, Stanimir Varbanov wrote:

<snip>

> 
> yes, there is a potential race between atomic_inc and dma callback. I
> reordered these calls to save few checks, and now it returns to me.
> 
> I imagine few options here:
> 
>  - reorder the dmaengine calls and atomic operations, i.e.
> call atomic_inc for rx and tx channels before corresponding
> dmaengine_submit and dmaengine_issue_pending.
> 
>  - have two different dma callbacks and two completions and waiting for
> the two.

This is probably the better solution.  The only thing you'll have to take into
consideration is that you may not have a RX DMA transactions.

> 
>  - manage to receive only one dma callback, i.e. the last transfer in
> case of presence of the rx_buf and tx_buf at the same time.

You use separate channels for the RX and TX, so as long as you have separate
callbacks, it shouldnt be a problem.


-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/