linux-kernel - Re: [RESEND PATCH v2 14/15] ASoC: qcom: apq8096: Add db820c machine driver

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Date:   Thu, 4 Jan 2018 13:44:30 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Mark Brown <broonie@...nel.org>,
        Stephen Boyd <sboyd@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Patrick Lai <plai@...eaurora.org>,
        Banajit Goswami <bgoswami@...eaurora.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH v2 14/15] ASoC: qcom: apq8096: Add db820c machine
 driver



On 04/01/18 12:02, Mark Brown wrote:
> On Wed, Jan 03, 2018 at 09:20:45AM -0800, Stephen Boyd wrote:
>> On 12/14/2017 09:34 AM, srinivas.kandagatla@...aro.org wrote:
> 
>>> uThis patch adds support to DB820c machine driver.
> 
>>> +	ret = dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(32));
> 
>> Why do we need to do this? Can you add some sort of comment in the code
>> about why?
> 
> And why are we applying DMA restrictions in a machine driver?

Initially I had this in pcm driver, but looking at example usage of 
snd_dma_alloc_pages, most of them use card->dev and some of them use pcm 
device for allocating dma memory.

Also, as I moved most dsp static services and dais out of DT, except 
codec and sound card, sound card device was the only choice I had for 
binding with iommu and enforcing iova range restrictions.

This call will be replaced by dma-ranges property in DT either way.


--srini
>