linux-kernel - Re: [PATCH 1/5] mtd: nand: omap2: Support parsing dma channel information from DT

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Date:	Wed, 14 Oct 2015 08:26:27 -0500
From:	"Franklin S Cooper Jr." <fcooper@...com>
To:	Roger Quadros <rogerq@...com>
CC:	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
	<nsekhar@...com>, <computersforpeace@...il.com>,
	<dwmw2@...radead.org>, <tony@...mide.com>
Subject: Re: [PATCH 1/5] mtd: nand: omap2: Support parsing dma channel
 information from DT



On 10/14/2015 06:52 AM, Roger Quadros wrote:
> Franklin,
>
> On 14/10/15 14:36, Roger Quadros wrote:
>> On 13/10/15 04:38, Franklin S Cooper Jr wrote:
>>> Switch from dma_request_channel to allow passing dma channel
>>> information from DT rather than hardcoding a value.
>>>
>>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
>> Acked-by: Roger Quadros <rogerq@...com>
>>
>>> ---
>>>  drivers/mtd/nand/omap2.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
>>> index d0f2620..957c32f 100644
>>> --- a/drivers/mtd/nand/omap2.c
>>> +++ b/drivers/mtd/nand/omap2.c
>>> @@ -1866,7 +1866,9 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>  		dma_cap_zero(mask);
>>>  		dma_cap_set(DMA_SLAVE, mask);
>>>  		sig = OMAP24XX_DMA_GPMC;
>>> -		info->dma = dma_request_channel(mask, omap_dma_filter_fn, &sig);
>>> +		info->dma = dma_request_slave_channel_compat(mask,
>>> +			omap_dma_filter_fn, &sig, pdev->dev.parent, "rxtx");
>>> +
> Just discovered that you are using the parent device node.
>
> How about moving the dma bindings to the nand node instead and using
> pdev->dev here?
Roger,

>From what I can tell the interrupt number and the dma channel will always be
the same no matter what. Doesn't matter if you have multiple nands or a
combination of nands and nors. Since that is the case I think it just makes
sense to leave it in the gpmc parent node and define it once.
>>>  		if (!info->dma) {
>>>  			dev_err(&pdev->dev, "DMA engine request failed\n");
>>>  			err = -ENXIO;
>>>
> cheers,
> -roger
>

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