On Thursday, September 01, 2011 12:09:18 PM Che-liang Chiou wrote: > Hi, > > Thanks for the insightful comments. Here are my responses: > > * Why don't I implement the divider in C? > It is not because I think it's performance critical (I haven't > benchmarked it yet), but because I have a probably wrong impression > that the divider has to be written in assembly --- all dividers in > arch/arm/lib/ are written in ARM assembly. What is the policy here for > using assembly or C?
No, C is just fine and is more generic. Those assembler versions are just optimized things, you don't need to be bothered by those. > > * When do we need a 64-bit divider? > In kernel code do_div() is used for various purposes. So I think it > should be quite often that we would need a 64-bit divider in U-Boot. Not much really ... and for the rare cases, we can do with do_div() as is. > > * Do we need a 64-64 bit divider? > do_div() defines 64-32 bit division semantics (dividend is 64-bit and > divisor is 32-bit), and this patch implements a 64-64 bit divider > (both dividend and divisor are 64-bit). I have to admit that I can't > think of scenarios or reasons to justify a 64-64 bit divider instead > of a 64-32 bit divider, except that a 64-64 bit divider is more > generic than a 64-32 bit one. So we don't need 64/64 divide at all. > > So I guess we can agree that a 64-bit divider is feature that is nice > to have, and we should decide: > * Do we need a 64-64 bit divider or a 64-32 bit one? 64-32 is do_div() > * Do we write it in C or assembly? C is OK. > > Depending on our decisions, I will rewrite (or abandon) this patch > accordingly. Look, I don't mean to be rough, but honestly. I see no use for this code. Adding code to anywhere so it'd just sit there is bad. Cheers > > Regards, > Che-Liang > > On Thu, Sep 1, 2011 at 4:03 AM, Wolfgang Denk <w...@denx.de> wrote: > > Dear Che-Liang Chiou, > > > > In message <1314787130-1043-1-git-send-email-clch...@chromium.org> you wrote: > >> This patch adds a 64-64 bit divider that supports ARMv4 and above. > > > > To summarize the misc feedback: Please explain in detail which > > problem you are trying to fix. We see no need for this patch so far. > > > > Best regards, > > > > Wolfgang Denk > > > > -- > > DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel > > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany > > Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de > > "Success covers a multitude of blunders." - George Bernard Shaw _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot