linux-kernel - Re: [Patch v6 2/2] dmaengine: add Qualcomm BAM dma driver

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Message-ID: <20140221172206.GB3102@qualcomm.com>
Date:	Fri, 21 Feb 2014 11:22:06 -0600
From:	Andy Gross <agross@...eaurora.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Patch v6 2/2] dmaengine: add Qualcomm BAM dma driver

On Fri, Feb 21, 2014 at 09:33:52AM +0000, Mark Rutland wrote:
> On Fri, Feb 21, 2014 at 06:43:05AM +0000, Andy Gross wrote:

[snip]
> > +       bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> 
> The binding document should describe the "bam_clk" string in the
> clock-names description.
> 

OK.

> > +       ret = of_property_read_u32(pdev->dev.of_node, "qcom,ee", &bdev->ee);
> > +       if (ret) {
> > +               dev_err(bdev->dev, "EE unspecified\n");
> 
> It would be nice to expand EE to what it stands for, at least in the
> error but possibly the binding too.

I can expand it to execution environment.  This is a trustzone thing and is
required from a security perspective.

> > +static const struct of_device_id bam_of_match[] = {
> > +       { .compatible = "qcom,bam-v1.4.0", },
> > +       { .compatible = "qcom,bam-v1.4.1", },
> 
> What are the differences between the two?
> 
> Is v1.4.1 an extension of v1.4.0?

On second look, the 1.4.1 has hardware fixes.  So the software API is the same.
I thought there were some configuration changes, but that isn't the case.

> Could you have the following in DTs:
> 
>   compatible = "qcom,bam-v1.4.1", "qcom,bam-v1.4.0";
> 
> Then you'd only need the v1.4.0 string in the driver for now.

Good point.  That's easy to change.

-- 
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