linux-kernel - RE: [PATCH 4/7] serial: ifx6x60: set SPI max_speed

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Date:	Thu, 6 Jan 2011 13:30:33 -0800
From:	"Gorby, Russ" <russ.gorby@...el.com>
To:	Alan Cox <alan@...ux.intel.com>
CC:	"gregkh@...e.de" <gregkh@...e.de>,
	"segoon@...nwall.com" <segoon@...nwall.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ahmed, Suhail" <suhail.ahmed@...el.com>
Subject: RE: [PATCH 4/7] serial: ifx6x60: set SPI max_speed_hz based on
 platform type

>-----Original Message-----
>From: Alan Cox [mailto:alan@...ux.intel.com]
>Sent: Wednesday, January 05, 2011 4:27 PM
>To: Gorby, Russ
>Cc: gregkh@...e.de; segoon@...nwall.com; Gorby, Russ; linux-
>kernel@...r.kernel.org; Ahmed, Suhail
>Subject: Re: [PATCH 4/7] serial: ifx6x60: set SPI max_speed_hz based on
>platform type
>
>> +	if (ifx_dev->is_6160)
>> +		spi->max_speed_hz = 12500000;
>> +	else
>> +		spi->max_speed_hz = 25000000;
>
>This should be coming directly from the platform data, ditto I suspect
>wiring the DMA to is_6160 should probably be a platform "use_dma"
>field ?
[Gorby, Russ]
OK I agree for the max clock rate, but I'm not so sure about the "use_dma" case.

Use_dma is used so the protocol driver matches the expectations (capabilities) of the controller driver it attaches to. In the general case I would think it could support several different controller drivers that might have differing capabilities. Currently the driver does assume the value of use_dma is constant for a platform so putting this indication in the platform data would suffice (for now) but to me, this is not really a platform attribute.
Is there a better way to handle this is?


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