On 11/19/19 2:20 PM, Tony Lindgren wrote: > * Andrew F. Davis <afd@xxxxxx> [191119 19:13]: >> On 11/19/19 2:07 PM, Tony Lindgren wrote: >>> * Andrew F. Davis <afd@xxxxxx> [191119 18:51]: >>>> On 11/19/19 1:32 PM, Tony Lindgren wrote: >>>>> It would allow us to completely change over to using >>>>> arm_smccc_smc() and forget the custom calls. >>>> >>>> We would need more than just the r12 quirk to replace all our custom SMC >>>> handlers, we would need quirks for omap_smc2 which puts process ID in r1 >>>> and puts #0xff in r6, and omap_smc3 that uses smc #1. All of our legacy >>>> SMC calls also trash r4-r11, that is very non SMCCC complaint as only >>>> r4-r7 need be caller saved. I don't see arm_smccc_smc() working with >>>> legacy ROM no matter how much we hack at it :( >>> >>> We would just have omap_smc2() call arm_smccc_smc() and in that >>> case. And omap_smc2() would still deal with saving and restoring >>> the registers. >> >> Then why call arm_smccc_smc()? omap_smc2() is already an assembly >> function, all it needs to do after loading the registers and saving the >> right ones is issue an "smc #0" instruction, why would we want to >> instead call into some other function to re-save registers and issue the >> exact same instruction? > > To use Linux generic API for smc calls where possible. > But we are not using generic API calls, we are using omap_smcx() which cannot call into arm_smccc_smc(). For all the above reasons plus arm_smccc_smc() uses r12 to save the stack pointer, our ROM expects r12 to store the function ID. >>> Certainly the wrapper functions calling arm_smccc_smc() can deal >>> with r12 too if the r12-quirk version and the plain version are >>> never needed the same time on a booted SoC. >>> >>> Are they ever needed the same time on a booted SoC or not? > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > They should not be needed at the same time, either OP-TEE is on the secure side or ROM is there. Andrew > Sorry but maybe check the font size on your screen. I'm trying to > get your attention again for the second time above to answer a > question I asked. > >>>> I can make OP-TEE also compatible with the r12 quirk, which is what I >>>> used to do. That way we didn't need to do any detection. The issue was >>>> that non-standard SMC calls should not go through the common SMCCC >>>> handler (unless you are QCOM for some reason..). >>> >>> Sounds like for optee nothing must be done for r12 :) > >> Unless all our calls use the r12 hack, then we would need to fixup >> OP-TEE to accept that also. > > No idea about that that part, but sounds like r12 use is up to > the caller in the optee case. > > Regards, > > Tony >
