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

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Message-ID: <yw1x1tanffqg.fsf@unicorn.mansr.com>
Date:	Tue, 15 Dec 2015 23:34:47 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH 1/3] ata: sata_dwc_460ex: use "dmas" DT property to find dma channel

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 */
+		};
+
 		SATA0: sata@...d1000 {
 			compatible = "amcc,sata-460ex";
-			reg = <4 0xbffd1000 0x800 4 0xbffd0800 0x400>;
+			reg = <4 0xbffd1000 0x800>;
 			interrupt-parent = <&UIC3>;
-			interrupts = <0x0 0x4       /* SATA */
-				      0x5 0x4>;     /* AHBDMA */
+			interrupts = <0x0 0x4>;
+			dmas = <&DMA0 0 0 1>;
+			dma-names = "sata-dma";
 		};
 
 		POB0: opb {


-- 
Måns Rullgård
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