On 11/24, Arnd Bergmann wrote: > On Monday 23 November 2015 15:13:52 Stephen Boyd wrote: > > On 11/23, Arnd Bergmann wrote: > > > > > > - PJ4/PJ4B (not PJ4B-MP) has a different custom opcode for udiv and sdiv > > > in ARM mode. We don't support that with true multiplatform kernels > > > because those opcodes work nowhere else, though with your proposed > > > series we could easily do that for dynamic patching. > > > > Do you have the information on these custom opcodes? I can work > > that into the patches assuming the MIDR is different. > > Thomas Petazzoni said this in a private mail: > > | According to the datasheet, the PJ4B has integer signed and unsigned > | divide, similar to the sdiv and udiv ARM instructions. But the way to > | access it is by doing a MRC instruction. > | > | MRC<cond> p6, 1, Rd , CRn , CRm, 4 > | > |for PJ4B is the same as: > | > | SDIV Rd , Rn, Rm > | > | on ARM cores. > | > |And: > | > | MRC<cond> p6, 1, Rd , CRn , CRm, 0 > | > |for PJ4B is the same as: > | > | UDIV Rd , Rn, Rm > | > |on ARM cores. > | > |This is documented in the "Extended instructions" section of the > |PJ4B datasheet. > > I assume what he meant was that this is true for both PJ4 and PJ4B > but not for PJ4B-MP, which has the normal udiv/sdiv instructions. > > IOW, anything with CPU implementer 0x56 part 0x581 should use those, > while part 0x584 can use the sdiv/udiv that it reports correctly. > It looks like we have some sort of function that mostly does this, except it doesn't differentiate on that lower bit for 1 vs 4. I guess I'll write another one for that. static inline int cpu_is_pj4(void) { unsigned int id; id = read_cpuid_id(); if ((id & 0xff0fff00) == 0x560f5800) return 1; return 0; } -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html