linux-kernel - Re: [PATCHv9] dmaengine: Add support for BCM2835

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Date:	Sat, 4 Jan 2014 16:27:57 +0100
From:	Florian Meier <florian.meier@...lo.de>
To:	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	devicetree <devicetree@...r.kernel.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>,
	linux-rpi-kernel <linux-rpi-kernel@...ts.infradead.org>,
	dmaengine <dmaengine@...r.kernel.org>,
	Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCHv9] dmaengine: Add support for BCM2835

On 02.01.2014 19:03, Arnd Bergmann wrote:
> On Thursday 02 January 2014 18:49:23 Florian Meier wrote:
>> Add support for DMA controller of BCM2835 as used in the Raspberry Pi.
>> Currently it only supports cyclic DMA.
>
> Looks very nice. Just a few details I noticed:
>
>> +#if defined(CONFIG_OF)
>> +static const struct of_device_id bcm2835_dma_of_match[] = {
>> + { .compatible = "brcm,bcm2835-dma", },
>> + {},
>> +};
>> +MODULE_DEVICE_TABLE(of, bcm2835_dma_of_match);
>> +#endif
>
> I doubt we are going to see non-DT versions of this driver, so the #ifdef
> can just get removed here.

As already explained in previous versions of this patch thread, there is
a non-DT version in a downstream kernel and the more I make this patch
incompatible with non-DT, the harder it gets to upstream the remaining
stuff. I hope this is not something that blocks this driver from getting
accepted.

> [...]
> This can now be simplified using the dma_get_any_slave_channel() interface
> taht Stephen Warren introduced.
> [...]
> dma_set_mask_and_coherent()

Sigh, the API is developing faster than I can keep track with updating
this patch. I hope some day I will be faster....
When Russell told me about the second one before, it hoped that I can
avoid merging different trees on my own, but it seems that you want me
to do that ;-)

>> + if (pdev->dev.of_node) {
>> + /* Device-tree DMA controller registration */
>> + rc = of_dma_controller_register(pdev->dev.of_node,
>> + bcm2835_dma_xlate, od);
>> + if (rc) {
>> + dev_err(&pdev->dev, "Failed to register DMA controller\n");
>> + goto err_no_dma;
>> + }
>> + }
>
> If pdev->dev.of_node isn't set, you didn't get here, so the if() can be removed.

Why not? (In the case of non-DT initialization)

Greetings,
Florian
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