linux-kernel - Re: [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue

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Date:	Fri, 2 Oct 2015 18:03:11 +0100
From:	Mark Brown <broonie@...nel.org>
To:	yitian <yitian.bu@...gramtek.com>
Cc:	alsa-devel@...a-project.org, wsa@...-dreams.de,
	linux-kernel@...r.kernel.org, Andrew.Jackson@....com,
	tiwai@...e.com, lgirdwood@...il.com, perex@...ex.cz,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue

On Thu, Oct 01, 2015 at 10:24:42AM +0800, yitian wrote:

> I think maybe two reasons:
> 1. designware I2S IP in my chipset(new design) is using tx empty and rx
> available signal as the DMA handshaking signal, but it may be not true
> for all chipsets. If I2S has separate signal as DMA handshaking signal, mask
> irq should not impact DMA transfer. But Synopsys's engineer recommend us to
> use
> tx and rx irq signal as the DMA handshaking signal, meanwhile we cannot find
> separate DMA handshaking signal from designware's IP spec, that's why tx/rx
> irq
> will impact DMA transfer.

If that's what the Synopsis engineers recommend I'd guess that other
integrations are doing the same thing.

> 2. I am using a FPGA for test, the cpu frequency of it is only 26MHz, that
> means
> XRUN is very easy to happen on my board. But I guess most of the developers
> are using real chipset which can have at least 600MHz frequency so XRUN is
> not easy to be reproduced. As my test, No XUN, no this bug...

Ah, that might be it - it might just be that other systems are working
due to race conditions.

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