On 11/19/19 2:44 PM, Tony Lindgren wrote: > * Andrew F. Davis <afd@xxxxxx> [191119 19:36]: >> 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. > > Saving and restoring r12 could be handled by the arm_smccc_smc() quirk > for the non-optee case. > > Then we could get rid of omap_smc1() and arm_smccc_smc() should work > for the optee case and non-optee case, right. > Yes, we could have both cases working if we could get the quirk in. >>>>> 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. > > OK thanks. So we could just modify the code dynamically on boot > based on if optee is found or not. The quirk could be done along > the lines of the qcom quirk but only for the non-optee case: > We wouldn't have to patch anything if we could get the quirk in. One has to state they wish to use the quirk version in a structure passed into arm_smccc_smc_quirk(), in which case for all legacy user we just fill out this quirk struct. OP-TEE uses the same arm_smccc_smc() but without the quirk struct and so it uses the compliant call. The issue is still the same, I tried adding this, I got NAKd, if you want to convince Mark to change his mind and allow us the quirk then we can go down this path. Otherwise this will remain a dead end. Andrew > $ git grep -C10 ARM_SMCCC_QUIRK_QCOM_A6 > > Regards, > > Tony >
