Re: [PATCH v3] OMAP: Fix for bus width which improves SD card's peformance.

[Nishanth Menon <nm@ti.com>]

Felipe Balbi had written, on 04/06/2010 11:32 AM, the following:
> On Tue, Apr 06, 2010 at 06:16:01PM +0200, ext Madhusudhan wrote:
>>
>>> -----Original Message-----
>>> From: Felipe Balbi [mailto:me@felipebalbi.com]
>>> Sent: Tuesday, April 06, 2010 12:01 AM
>>> To: Madhusudhan
>>> Cc: me@felipebalbi.com; 'kishore kadiyala'; 'Vimal Singh';
>>> tony@atomide.com; svenkatr@ti.com; linux-omap@vger.kernel.org; linux-
>>> kernel@vger.kernel.org; jarkko.lavinen@nokia.com
>>> Subject: Re: [PATCH v3] OMAP: Fix for bus width which improves SD card's
>>> peformance.
>>>
>>> Hi,
>>>
>>> On Mon, Apr 05, 2010 at 12:19:29PM -0500, Madhusudhan wrote:
>>>> Since the first if command already checks for the 8-bit the second check
>>>> like >= 4 is definitely not readable in my opinion.
>>> how come ???
>>>
>>>> Functionally do you see anything wrong with this patch??
>>> functionally no, but (hypothetical situation) and if on
>>> omap4/5/6/whatever, omap controller supports a bigger bus width then
>>> you'll have to add a line like:
>>>
>>> +	if (mmc_slot(host).wires == 16)
>>> +		mmc->caps |= (MMC_CAP_16_BIT_DATA | MMC_CAP_8_BIT_DATA |
>>> +				MMC_CAP_4_BIT_DATA);
>>> -	if (mmc_slot(host).wires == 8)
>>> +	else if (mmc_slot(host).wires == 8)
>>>
>>> do you see the problem ?? In my opinion it doesn't scale well.
>>>
>> The point we should note here is that MMC spec supports a max bus width of
>> 8-bit. So anything beyond 8-bit is not in the picture as of today.
> 
> in that case, the code could be:
> 
> WARN_ON(mmc_slot(host).wires > 8);
> 
> if (mmc_slot(host).wires == 8)
> 	mmc->caps |= MMC_CAP_8_BIT_DATA;
> if (mmc_slot(host).wires >= 4)
> 	mmc->caps |= MMC_CAP_4_BIT_DATA;
>
some reasons why i love switch statements ;) since I dont expect other 
than precisely 4 and 8 (do we expect 5,6,7 - i might be wrong).. but if 
it is so, wont the following be better?

switch (mmc_slot(host).wires)
{
case 8:
	mmc->caps |= MMC_CAP_8_BIT_DATA;
	/* fall thru*/
case 4:
	mmc->caps |= MMC_CAP_4_BIT_DATA;
		break;
default:
	WARN("bad width");
}	
-- 
Regards,
Nishanth Menon