[U-Boot] [PATCH 3/4 V2] OneNAND: Add simple OneNAND SPL

[Scott Wood]

On 11/02/2011 07:15 PM, Marek Vasut wrote:
>> On 11/01/2011 05:54 PM, Marek Vasut wrote:
>>> +static void spl_onenand_get_geometry(struct spl_onenand_data *data)
>>> +{
> [...]
> 
>>> +	/* The page can be either 2k or 4k, avoid using DIV_ROUND_UP. */
>>> +	if (data.pagesize == 2048) {
>>> +		total_pages = len / 2048;
>>> +		page = offset / 2048;
>>> +		total_pages += !!(len & 2047);
>>> +	} else if (data.pagesize == 4096) {
>>> +		total_pages = len / 4096;
>>> +		page = offset / 4096;
>>> +		total_pages += !!(len & 4095);
>>> +	}
>>
>> What's wrong with DIV_ROUND_UP?  It should produce smaller code than
>> what you've done here...
> 
> It pulls in aeabi_*div* functions, which won't fit into block 0 of Onenand.

It shouldn't do that if the divisor is a constant power of 2.  The
compiler will turn it into a shift, just like with the other divides in
the above code fragment.

You can't use DIV_ROUND_UP directly on data.pagesize, but you can use it
in each branch of the if statement instead of that awkward and slightly
more expensive !!(len & 4095) construct.

-Scott