Re: [PATCH v1 1/2] sata_dwc_460ex: move to generic DMA driver

Andy Shevchenko [off-list ref] writes:

On Sun, 2015-11-22 at 13:03 +0000, M=E5ns Rullg=E5rd wrote:

quoted

Andy Shevchenko [off-list ref] writes:
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quoted

The SATA implementation based on two actually different devices,
i.e. SATA and
DMA controllers.
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For Synopsys DesignWare DMA we have already a generic
implementation of the
driver. Thus, the patch converts the code to use DMAEngine
framework and
dw_dmac driver.
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In future it will be better to split the devices inside DTS as well
like it's
done on other platforms.

quoted

quoted

@@ -1721,16 +1227,16 @@ static int sata_dwc_probe(struct

platform_device *ofdev)
 		   idr, ver[0], ver[1], ver[2]);
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 	/* Get SATA DMA interrupt number */
-	irq =3D irq_of_parse_and_map(np, 1);
-	if (irq =3D=3D NO_IRQ) {
+	hsdev->dma->irq =3D irq_of_parse_and_map(np, 1);

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This doesn't look like it has been more than compile-tested.

Yes, that's true, my question [1] was a crying in the wilderness.

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  Nothing
ever allocates hsdev->dma, so it can't possibly work.

You are right.

quoted

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Also, has anyone given any thought to getting rid of the dependency
on the DW DMA controller?

How? Before it was even more harder link to it (embedded routines).

It already uses the dmaengine API to do the transfers.  To make it
generic, two things need to change:

1. The DMA controller should get its own DT node instead of the SATA
   driver calling dw_dma_probe() directly.

2. The SATA driver can then use dma_request_slave_channel() and a "dmas"
   DT property instead of dma_request_channel() and filter function.

The changes are easy to make as such.  The only problem is that we need
to preserve compatibility with old device trees.

On the other hand you may introduce dma_ops and use them like it's
done, for example, in spi-dw*.c

quoted

  Presumably support for old device trees would
need to be retained for compatibility.  Maybe checking for a "dmas"
property and falling back on the current behaviour if it's missing.=20=20

I didn't get how DT is related to DW or any other DMAC used with this
SATA controller.

See Documentation/devicetree/bindings/dma/dma.txt

quoted

My goal is to get this driver working with another chip using the
same SATA controller but a different DMA engine.

It would be nice to eventually bring this working with generic DMA
Engine API. Please, keep me in Cc list regarding this driver.

What's your interest in this driver if you don't have the hardware?

--=20
M=E5ns Rullg=E5rd
mans@mansr.com