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 18:53:04 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Måns Rullgård <mans@...sr.com>,
	Julian Margetson <runaway@...dw.ms>
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

On Thu, 2015-12-17 at 16:04 +0000, Måns Rullgård wrote:
> 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.

It's currently broken, last person who seems to have it is
(was?) Julian Margetson [1]

[1] https://patchwork.ozlabs.org/patch/439850/

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy

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