>From 788bfd45e7ce521666a19dba99277106e4d33c80 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker Date: Tue, 11 Jun 2024 19:15:30 +0100 Subject: [PATCH 1/2] firmware/psci: Add psci_early_test_conduit() Add a function to test early if PSCI is present and what conduit it uses. Because the PSCI conduit corresponds to the SMCCC one, this will let the kernel know whether it can use SMC instructions to discuss with the Realm Management Monitor (RMM), early enough to enable RAM and serial access when running in a Realm. Signed-off-by: Jean-Philippe Brucker --- include/linux/psci.h | 5 +++++ drivers/firmware/psci/psci.c | 25 +++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/include/linux/psci.h b/include/linux/psci.h index 4ca0060a3fc4..a1fc1703ba20 100644 --- a/include/linux/psci.h +++ b/include/linux/psci.h @@ -45,8 +45,13 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void); #if defined(CONFIG_ARM_PSCI_FW) int __init psci_dt_init(void); +bool __init psci_early_test_conduit(enum arm_smccc_conduit conduit); #else static inline int psci_dt_init(void) { return 0; } +static inline bool psci_early_test_conduit(enum arm_smccc_conduit conduit) +{ + return false; +} #endif #if defined(CONFIG_ARM_PSCI_FW) && defined(CONFIG_ACPI) diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c index d9629ff87861..a40dcaf17822 100644 --- a/drivers/firmware/psci/psci.c +++ b/drivers/firmware/psci/psci.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -767,6 +768,30 @@ int __init psci_dt_init(void) return ret; } +/* + * Test early if PSCI is supported, and if its conduit matches @conduit + */ +bool __init psci_early_test_conduit(enum arm_smccc_conduit conduit) +{ + int len; + int psci_node; + const char *method; + unsigned long dt_root; + + /* DT hasn't been unflattened yet, we have to work with the flat blob */ + dt_root = of_get_flat_dt_root(); + psci_node = of_get_flat_dt_subnode_by_name(dt_root, "psci"); + if (psci_node <= 0) + return false; + + method = of_get_flat_dt_prop(psci_node, "method", &len); + if (!method) + return false; + + return (conduit == SMCCC_CONDUIT_SMC && strncmp(method, "smc", len) == 0) || + (conduit == SMCCC_CONDUIT_HVC && strncmp(method, "hvc", len) == 0); +} + #ifdef CONFIG_ACPI /* * We use PSCI 0.2+ when ACPI is deployed on ARM64 and it's -- 2.45.2