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

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Message-ID: <561E6791.3030404@ti.com>
Date:	Wed, 14 Oct 2015 09:32:49 -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 09:11 AM, Roger Quadros wrote:
> On 14/10/15 16:26, Franklin S Cooper Jr. wrote:
>>
>> 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.
> Is prefetch/writepost dma used for NOR or any other GPMC peripheral
> or only for NAND?
The dma seems tied to the prefetch. From what I can tell the prefetch is only
used by nand.
>
> Let's also get Tony's inputs on this.
Sure.
>
>>>>>  		if (!info->dma) {
>>>>>  			dev_err(&pdev->dev, "DMA engine request failed\n");
>>>>>  			err = -ENXIO;
>>>>>
> --
> cheers,
> -roger

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