On 8/19/24 11:19 PM, Steven Price wrote:
From: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> 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 <jean-philippe@xxxxxxxxxx> Signed-off-by: Steven Price <steven.price@xxxxxxx> --- v4: New patch --- drivers/firmware/psci/psci.c | 25 +++++++++++++++++++++++++ include/linux/psci.h | 5 +++++ 2 files changed, 30 insertions(+)
Question: Do we need same check for ACPI based system?
diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c index 2328ca58bba6..2b308f97ef2c 100644 --- a/drivers/firmware/psci/psci.c +++ b/drivers/firmware/psci/psci.c @@ -13,6 +13,7 @@ #include <linux/errno.h> #include <linux/linkage.h> #include <linux/of.h> +#include <linux/of_fdt.h> #include <linux/pm.h> #include <linux/printk.h> #include <linux/psci.h> @@ -769,6 +770,30 @@ int __init psci_dt_init(void) return ret; }+/*+ * Test early if PSCI is supported, and if its conduit matches @conduit + */
Nit: The comments needn't span into multiple lines.
+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;
+
Nit: Strictly speaking, "psci_node == 0" isn't an error. So the check would be "if (psci_node < 0)" if I'm correct.
+ 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 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)
Thanks, Gavin
