linux-kernel - Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

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Date:	Thu, 17 Dec 2015 16:04:56 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Tejun Heo <tj@...nel.org>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

Andy Shevchenko <andriy.shevchenko@...ux.intel.com> writes:

> On Thu, 2015-12-17 at 15:13 +0000, Måns Rullgård wrote:
>> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> writes:
>> 
>> > On Tue, 2015-12-15 at 23:34 +0000, Måns Rullgård wrote:
>> > > Mans Rullgard <mans@...sr.com> writes:
>> > > 
>> > > > Currently this driver only works with a DesignWare DMA engine
>> > > > which it registers manually using the second "reg" address
>> > > > range and interrupt number from the DT node.
>> > > > 
>> > > > This patch makes the driver instead use the "dmas" property if
>> > > > present, otherwise optionally falling back on the old way so
>> > > > existing device trees can continue to work.
>> > > > 
>> > > > With this change, there is no longer any reason to depend on
>> > > > the 460EX machine type so drop that from Kconfig.
>> > > > 
>> > > > Signed-off-by: Mans Rullgard <mans@...sr.com>
>> > > > ---
>> > > >  drivers/ata/Kconfig          |  10 ++-
>> > > >  drivers/ata/sata_dwc_460ex.c | 192
>> > > > +++++++++++++++++++++++++++--
>> > > > --------------
>> > > >  2 files changed, 131 insertions(+), 71 deletions(-)
>> > > 
>> > > The corresponding patch for the canyonlands devicetree looks
>> > > something
>> > > like this.  I don't have any such hardware or even a manual, so I
>> > > don't
>> > > know what values to use for the various required DT properties of
>> > > the
>> > > DMA controller node, nor can I test it.  The SATA driver works
>> > > with a
>> > > different DMA controller on a Sigma Designs chip.
>> > > 
>> > > diff --git a/arch/powerpc/boot/dts/canyonlands.dts
>> > > b/arch/powerpc/boot/dts/canyonlands.dts
>> > > index 3dc75de..959f36e 100644
>> > > --- a/arch/powerpc/boot/dts/canyonlands.dts
>> > > +++ b/arch/powerpc/boot/dts/canyonlands.dts
>> > > @@ -190,12 +190,22 @@
>> > >  					 /* DMA */ 0x2 &UIC0 0xc
>> > > 0x4>;
>> > >  		};
>> > >  
>> > > +		DMA0: dma@...d0800 {
>> > > +			compatible = "snps,dma-spear1340";
>> > > +			reg = <4 0xbffd0800 0x400>;
>> > > +			interrupt-parent = <&UIC3>;
>> > > +			interrupts = <0x5 0x4>;
>> > > +			#dma-cells = <3>;
>> > > +			/* required properties here */
>> > 
>> > You have to move the master assignments and other custom dw_dmac
>> > properties. Maybe at some point I will fix that in dw/platform.c.
>> > 
>> > > +		};
>> 
>> The current sata_dwc driver calls dw_dma_probe() with null pdata
>> which causes the dw_dma driver to auto-detect most parameters.  It
>> looks like simply omitting those properties here results in the same
>> thing, although in this case dw_dma_parse_dt() leaves a
>> devm-allocated pdata struct adrift.  Deferring the allocation of that
>> and changing the DT binding doc to make these properties optional for
>> auto-detect-capable hardware should just work.
>
> Yeah, I would like to allow autoconfiguration in case of DT as well and
> translate it to use unified device property API.
>
>> Something like this:
>
> If it works for you, please, submit as a patch. Thanks.

I can't test it since I have no such hardware.

-- 
Måns Rullgård
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