Hi Igor, On Thu, Feb 1, 2024 at 10:36 PM Igor Opaniuk <[email protected]> wrote: > > Hello Weizhao, > > On Wed, Jan 31, 2024 at 3:15 PM Weizhao Ouyang <[email protected]> wrote: > > > > According to PSCI specification DEN0022F, PSCI_FEATURES is used to check > > whether the SMCCC is implemented by discovering SMCCC_VERSION. > > > Could you please add more details to your commit message or as a comment > explaining what exact steps should be done for a full discovery sequence of > Arm > Architecture Service functions, so people don't need to search for > that information explicitly? > > For instance: > Step 1: Determine if SMCCC_VERSION is implemented > - Use firmware data, device tree PSCI node, or ACPI FADT PSCI flag, to > determine whether a > PSCI implementation is present. > - Use PSCI_VERSION to learn whether PSCI_FEATURES is provided. PSCI_FEATURES > is > mandatory from version 1.0 of PSCI > Step 2. etc. > > I would just pull that info from the latest SMC Calling Convention version > 1.5, > from 9 Appendix B: Discovery of Arm Architecture Service functions. > > Thank you! > > Signed-off-by: Weizhao Ouyang <[email protected]> > > --- > > v3: remove fallback smc call > > v2: check SMCCC_ARCH_FEATURES > > --- > > drivers/firmware/psci.c | 5 ++++- > > include/linux/arm-smccc.h | 6 ++++++ > > 2 files changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c > > index c6b9efab41..03544d76ed 100644 > > --- a/drivers/firmware/psci.c > > +++ b/drivers/firmware/psci.c > > @@ -135,10 +135,13 @@ static int bind_smccc_features(struct udevice *dev, > > int psci_method) > > PSCI_VERSION_MAJOR(psci_0_2_get_version()) == 0) > > return 0; > > > > - if (request_psci_features(ARM_SMCCC_ARCH_FEATURES) == > > + if (request_psci_features(ARM_SMCCC_VERSION) == > > PSCI_RET_NOT_SUPPORTED) > > return 0; > > > > + if (invoke_psci_fn(ARM_SMCCC_VERSION, 0, 0, 0) < > > ARM_SMCCC_VERSION_1_1) > > + return 0; > > + > IMO, to fully comply with SMC Calling Convention version 1.5 > we should also check for SMCCC_ARCH_WORKAROUND_1: > > From 9 Appendix B: Discovery of Arm Architecture Service functions, > Step 2: Determine if Arm Architecture Service function is implemented > - Use SMCCC_VERSION to learn whether the calling convention complies > to version 1.1 or above. > - Use SMCCC_ARCH_FEATURES to query whether the Arm Architecture > Service function is implemented > on this system <--- we lack of this step
Thanks for your review. The 9 Appendix B describes an approach to discovery the maximize ability without causing unsafe behavior on existing platforms. Regarding the second step, it is just using SMCCC_ARCH_WORKAROUND_1 as an example to test SMCCC_ARCH_FEATURES. For the U-Boot case, we can revisit this from two perspectives: 1. SMCCC_ARCH_FEATURES is MANDATORY from SMCCC v1.1. 2. SMCCC_VERSION is OPTIONAL for SMCCC v1.0, so we should consider a safe behavior. 3. U-Boot is using CONFIG_ARM_SMCCC_FEATURES to probe and bind SMCCC service driver if this driver is reported as supported. 4. U-Boot SMCCC service driver can embed its discovery process in is_supported() callback. So now we can choose the following approach in U-Boot: - Use firmware data (check "arm,psci-1.0") to determine whether a PSCI implementation is present. - Use PSCI_VERSION (psci_0_2_get_version() major version >= 0) to learn whether PSCI_FEATURES is provided. - Use PSCI_FEATURES with the SMCCC_VERSION Function Identifier as a parameter to determine that SMCCC_VERSION is implemented. - Use SMCCC_VERSION to learn whether the calling convention complies to version 1.1 or above. - Trying to probe and bind SMCCC service driver. BR, Weizhao > > > if (psci_method == PSCI_METHOD_HVC) > > pdata->invoke_fn = smccc_invoke_hvc; > > else > > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > > index f44e9e8f93..da3d29aabe 100644 > > --- a/include/linux/arm-smccc.h > > +++ b/include/linux/arm-smccc.h > > @@ -55,8 +55,14 @@ > > #define ARM_SMCCC_QUIRK_NONE 0 > > #define ARM_SMCCC_QUIRK_QCOM_A6 1 /* Save/restore register > > a6 */ > > > > +#define ARM_SMCCC_VERSION 0x80000000 > > #define ARM_SMCCC_ARCH_FEATURES 0x80000001 > > > > +#define ARM_SMCCC_VERSION_1_0 0x10000 > > +#define ARM_SMCCC_VERSION_1_1 0x10001 > > +#define ARM_SMCCC_VERSION_1_2 0x10002 > > +#define ARM_SMCCC_VERSION_1_3 0x10003 > > + > > #define ARM_SMCCC_RET_NOT_SUPPORTED ((unsigned long)-1) > > > > #ifndef __ASSEMBLY__ > > -- > > 2.39.2 > > > > > -- > Best regards - Freundliche Grüsse - Meilleures salutations > > Igor Opaniuk > Senior Software Engineer, Embedded & Security > E: [email protected] > W: www.foundries.io
