Re: [PATCH v2] spi: orion: support armada extended baud rates

[Greg Ungerer <gerg-JBU5SbJe1FlAfugRpC6u6w@public.gmane.org>]

Hi Ezequiel,

On 06/09/14 22:06, Ezequiel Garcia wrote:
> Hi Greg,
>
> (Ccing mvebu guys, full discussion here: http://www.spinics.net/lists/devicetree/msg47806.html)
>
> On 05 Sep 11:11 PM, Greg Ungerer wrote:
>> On 05/09/14 17:36, Geert Uytterhoeven wrote:
>>> No, the other way around (from most-specific to least-specific):
>>>
>>>      compatible = "marvell,armada-spi", "marvell,orion-spi"
>>>
>>> So the Armada version is used if available, and the Orion version
>>> is used as a fallback.
> Since you are doing another spin, please split this in two patches.
> The driver and devicetree binding documentation should be in one patch,
> and the devicetree .dtsi change in another patch.
>
> By following Geert's request about the compatible, you make sure both
> patches can be merged through different maintainers, and that an old devicetree
> blob can be used safely.

Sure, yes, I would prefer that too. I didn't do it for this because 
checkpatch
complained for the spi-orion.c change in its own:

WARNING: DT compatible string "marvell,armada-spi" appears un-documented 
-- check ./Documentation/devicetree/bindings/
#170: FILE: drivers/spi/spi-orion.c:412:
+    { .compatible = "marvell,armada-spi", .data = &armada_spi_dev_data, },

But I am happy to ignore that :-)


>>>   Also what about armada370-xp, armada375, armada380
>>> and any other variants out there?
>> I don't know. I don't have access to functional specs for anything
>> other than the 370. I expect they are probably the same though.
>> (Can anyone confirm?)
>>
> Confirmed. Judging from the specs, seems the same SPI IP is on all the
> Armada SoCs; you can do the 'armada-spi' compatible addition on 375 and 38x.
>
> Did a few tests on the AXP-GP board (which has an SPI flash) using
> 'orion-spi' and 'armada-spi' compatibles.
>
> Tested-by: Ezequiel Garcia <ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> Reviewed-by: Ezequiel Garcia <ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

Thanks, appreciate that.


> I haven't been able to spot any speed difference, though (perhaps my
> test is too limited?), so I wonder if there's any improvement with this
> patch?

Try setting a speed like 2MHz for an SPI device. It will fail because that
is below the minimum divisor it can calculate with the old orion style
behavior. I have an armada 370 based board with an ethernet switch
that is controlled by SPI. Its typical SPI bus speed is 2MHz, that is how I
came up against this.

Regards
Greg

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