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From: Andy Gross <>
To: Stanimir Varbanov <>
Cc: Mark Brown <>,,,,,
	Rob Herring <>,
	Mark Rutland <>,
	Kumar Gala <>,
	Sagar Dharia <>,
	Daniel Sneddon <>
Subject: Re: [PATCH v2] spi: qup: Add DMA capabilities
Date: Tue, 24 Feb 2015 16:38:40 -0600	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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


> 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

  reply	other threads:[~2015-02-24 22:38 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-24 13:00 Stanimir Varbanov
2015-02-24 13:56 ` Mark Brown
2015-02-24 16:08   ` Stanimir Varbanov
2015-02-24 22:38     ` Andy Gross [this message]
2015-02-26  2:33     ` Mark Brown
2015-02-27 14:46       ` Stanimir Varbanov
2015-02-24 16:09 ` Ivan T. Ivanov
2015-02-24 17:11 ` Ivan T. Ivanov

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