Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes:
> On Sun, 2015-11-22 at 13:03 +0000, Måns Rullgård wrote:
>> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes:
>>
>> > The SATA implementation based on two actually different devices,
>> > i.e. SATA and
>> > DMA controllers.
>> >
>> > 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.
>> >
>> > In future it will be better to split the devices inside DTS as well
>> > like it's
>> > done on other platforms.
>
>> > @@ -1721,16 +1227,16 @@ static int sata_dwc_probe(struct
>> > platform_device *ofdev)
>> > idr, ver[0], ver[1], ver[2]);
>> >
>> > /* Get SATA DMA interrupt number */
>> > - irq = irq_of_parse_and_map(np, 1);
>> > - if (irq == NO_IRQ) {
>> > + hsdev->dma->irq = irq_of_parse_and_map(np, 1);
>>
>> 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.
>
>> Nothing
>> ever allocates hsdev->dma, so it can't possibly work.
>
> You are right.
>
>>
>> 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
>
>> 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.
>
> 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
>> 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?
--
Måns Rullgård
mans@xxxxxxxxx
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