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

[Marek Vasut]

> 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.

Expensive in what way? Either way, I don't think this matters that much.