linux-kernel - Re: [PATCH 02/14] dmaengine: dma-jz4780: Separate chan/ctrl registers

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Message-Id: <1531350785.2021.0@smtp.crapouillou.net>
Date:   Thu, 12 Jul 2018 01:13:05 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Vinod <vkoul@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Daniel Silsby <dansilsby@...il.com>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...ux-mips.org
Subject: Re: [PATCH 02/14] dmaengine: dma-jz4780: Separate chan/ctrl registers



Le mer. 11 juil. 2018 à 14:16, Vinod <vkoul@...nel.org> a écrit :
> On 10-07-18, 17:36, Paul Cercueil wrote:
> 
>>  > >  @@ -3,7 +3,8 @@
>>  > >   Required properties:
>>  > >
>>  > >   - compatible: Should be "ingenic,jz4780-dma"
>>  > >  -- reg: Should contain the DMA controller registers location 
>> and
>>  > > length.
>>  > >  +- reg: Should contain the DMA channel registers location and
>>  > > length, followed
>>  > >  +  by the DMA controller registers location and length.
>>  > >   - interrupts: Should contain the interrupt specifier of the 
>> DMA
>>  > > controller.
>>  > >   - interrupt-parent: Should be the phandle of the interrupt
>>  > > controller that
>>  > >   - clocks: Should contain a clock specifier for the JZ4780 PDMA
>>  > > clock.
>>  > >  @@ -22,7 +23,8 @@ Example:
>>  > >
>>  > >   dma: dma@...20000 {
>>  > >   	compatible = "ingenic,jz4780-dma";
>>  > >  -	reg = <0x13420000 0x10000>;
>>  > >  +	reg = <0x13420000 0x400
>>  > >  +	       0x13421000 0x40>;
>>  >
>>  > Second should be optional or we break platform which may not have
>>  > updated DT..
>> 
>>  See comment below.
>> 
>>  > >  -	jzdma->base = devm_ioremap_resource(dev, res);
>>  > >  -	if (IS_ERR(jzdma->base))
>>  > >  -		return PTR_ERR(jzdma->base);
>>  > >  +	jzdma->chn_base = devm_ioremap_resource(dev, res);
>>  > >  +	if (IS_ERR(jzdma->chn_base))
>>  > >  +		return PTR_ERR(jzdma->chn_base);
>>  > >  +
>>  > >  +	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>>  > >  +	if (!res) {
>>  > >  +		dev_err(dev, "failed to get I/O memory\n");
>>  > >  +		return -EINVAL;
>>  > >  +	}
>>  >
>>  > okay and this breaks if you happen to get probed on older DT. I 
>> think DT
>>  > is treated as ABI so you need to continue support older method 
>> while
>>  > finding if DT has split resources
>> 
>>  See my response to PrasannaKumar. All the Ingenic-based boards do 
>> compile
>>  the devicetree within the kernel, so I think it's still fine to add 
>> breaking
>>  changes. I'll wait on @Rob to give his point of view on this, 
>> though.
>> 
>>  (It's not something hard to change, but I'd like to know what's the 
>> policy
>>  in that case. I have other DT-breaking patches to submit)
> 
> The policy is that DT is an ABI and should not break :)
> 
> Who maintains Ingenic arch. MAINTAINERS doesn't tell me.

Unofficially that would be me :)

Otherwise that would be the MIPS maintainers, Ralf and Paul (Burton).

> --
> ~Vinod