On Mon, 2013-10-07 at 22:58 -0500, Wang Dongsheng-B40534 wrote: > > > -----Original Message----- > > From: Wood Scott-B07421 > > Sent: Tuesday, October 01, 2013 7:06 AM > > To: Wang Dongsheng-B40534 > > Cc: Wood Scott-B07421; Bhushan Bharat-R65777; linuxppc- > > d...@lists.ozlabs.org > > Subject: Re: [PATCH v4 4/4] powerpc/85xx: add sysfs for pw20 state and > > altivec idle > > > > On Sun, 2013-09-29 at 01:57 -0500, Wang Dongsheng-B40534 wrote: > > > I think we need to do this: > > > > > > #define U64_LOW_MASK 0xffffffffULL > > > #define U64_MASK 0xffffffffffffffffULL > > > > > > u32 tmp_rem; > > > u64 ns_u_rem, ns_u, ns_l, ns_l_carry; > > > u64 cycle; > > > > > > ns_u = ns >> 32; > > > ns_l = ns & U64_LOW_MASK; > > > > > > ns_l *= tb_ticks_per_usec; > > > ns_l_carry = ns_l >> 32; > > > ns_u *= tb_ticks_per_usec; > > > ns_u += ns_l_carry; > > > > > > ns_u = div_u64_rem(ns_u, 1000, &tmp_rem); > > > ns_u_rem = tmp_rem; > > > ns_l = (ns_l & U64_LOW_MASK) | ((ns_u_rem) << 32); > > > ns_l = div_u64(ns_l, 1000); > > > > > > if (ns_u >> 32) > > > cycle = U64_MASK; > > > else > > > cycle = (ns_u << 32) | (ns_l & U64_LOW_MASK); > > > > > > I has already tested this code, and works good. :) > > > > Ugh. I don't think we need to get this complicated (and I'd rather not > > spend the time verifying the correctness of this). > > > > If for some reason we did need something like this in some other context > > (I don't want to see it just for pw20), I'd be more inclined to see > > general 128-bit mult/divide support. > > > I would like to use my version,:), because it can handle any situation and we > do not need to restrict users.
It also would take more time to review than I have to spend on it, not to mention the impact on anyone in the future that wants to understand or maintain this code -- all for very unlikely situations (and the "failure" in those very unlikely situations is just that we go into PW20 more often than intended). -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
