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Consequently the SMCCC >>> call must use the AArch64 calling convention, which requires bit 30 of >>> the FID to be set. The spec is a bit confusing here, since it mentions >>> that in the parameter description ("2: SoC name (optionally implemented for >>> SMC64 calls, ..."), but still prints the FID explicitly as 0x80000002. >>> But as this FID is using the SMC32 calling convention (correct for the >>> other two calls), it will not match what mainline TF-A is expecting, so >>> any call would return NOT_SUPPORTED. >>> >> >> Good catch and I must admit I completely missed it inspite of discussing >> 32b vs 64b FID around the same time this was introduced. >> >>> Add a 64-bit version of the ARCH_SOC_ID FID macro, and use that for the >>> SoC name version of the call. >>> >>> Fixes: 5f9c23abc477 ("firmware: smccc: Support optional Arm SMCCC SOC_ID name") >>> Signed-off-by: Andre Przywara >>> --- >>> Hi, >>> >>> as somewhat expected, this now fails on an Ampere machine, which >>> reported a string in /sys/devices/soc0/machine before, but is now missing >>> this file. >>> Any idea what's the best way to handle this? Let the code try the 32-bit >>> FID, when the 64-bit one fails? Or handle this as some kind of erratum? >>> >> >> Not sure about it yet. Erratum seems good option so that we can avoid >> others getting it wrong too as they might just run the kernel and be happy >> if the machine sysfs shows up as we decided to do fallback to 32b FID. >> >> I will start a discussion to get the spec updated and pushed out and see >> how that goes. >> >> The change itself looks good and happy to get it merged once we know >> what is the best approach(erratum vs fallback). >> > > Looking at the SMCCC spec(DEN0028 v1.6 G Edition) -> > Section 7.4.6 Implementation responsibilities > > If implemented, the firmware: > ... > • must not implement SoC_ID_type == 2 for SMC32. > • can optionally implement SoC_ID_type == 2 for SMC64 (Function ID 0xC000_0002), > ... > > So Ampere is not spec conformant here and hence I prefer to handle it as > erratum. Hopefully we can use SOC_ID version and revision to keep the scope > of erratum confined to smallest set of platforms. > > Paul, > > Thoughts ? > Am I correctly understanding that, if the SMC64 SOC_ID Name call fails, rather than an unconditional fallback to the SMC32 call, the SMC32 fallback would only be occurring under the proposed erratum? I brought this issue up at a weekly team meeting today, and I'll also be communicating with the Ampere Computing firmware team regarding this issue.