On Fri, 30 Sep 2016 19:25:17 +0200
Arnd Bergmann <a...@arndb.de> wrote:
> On Friday 30 September 2016, Boris Brezillon wrote:
> > > + /* copy into possibly unaligned OOB region with actual length */
> > > + memcpy(data + bytes, eccdata, len);
> >
> > Is it better than
> >
> > for (i = 0; i < len; i += 4) {
> > u32 val = __raw_readl(ecc->regs + ECC_ENCPAR(i / 4));
> >
> > memcpy(data + bytes + i, &val, min(len, 4));
> > }
> >
> > I'm probably missing something, but what's the point of creating a
> > temporary buffer of 112 bytes on the stack since you'll have to copy
> > this data to the oob buffer at some point?
>
>
> I tried something like that first, but wasn't too happy with it for
> a number of small reasons:
>
> - __raw_readl in a driver is not usually the right API, __memcpy32_from_io
> uses it internally, but it's better for a driver not to rely on that,
> in case we need some barriers (which we may in factt need for other
> drivers).
I agree, even though calling something prefixed with __ (in this case,
__ioread32_copy()) sounds like a bad thing too :).
>
> - the min(len,4) expression is incorrect, fixing that makes it more
> complicated
> again
Sorry, it's min(len - i, 4), which is not that complicated :P.
>
> - I didn't like to call memcpy() multiple times, as that might get turned
> into an external function call (the compiler is free to optimize small
> memcpy calls or not).
Okay.
>
> I agree that he 112 byte buffer isn't ideal either, it just seemed to
> be the lesser annoyance.
How about we keep your approach, but put the buffer in the mtk_ecc
struct?
