firmware: psci: bind arm smccc features when discovered

Use PSCI device to query Arm SMCCC v1.1 support from secure monitor
and if so, bind drivers for the SMCCC features that monitor supports.

Drivers willing to be bound from Arm SMCCC features discovery can use
macro ARM_SMCCC_FEATURE_DRIVER() to register to smccc feature discovery,
providing target driver name and a callback function that returns
whether or not the SMCCC feature is supported by the system.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

drivers/firmware/Kconfig

@@ -37,4 +37,12 @@ config ZYNQMP_FIRMWARE
 	  Say yes to enable ZynqMP firmware interface driver.
 	  If in doubt, say N.
 
+config ARM_SMCCC_FEATURES
+	bool "Arm SMCCC features discovery"
+	depends on ARM_PSCI_FW
+	help
+	  Discover Arm SMCCC features for which a U-Boot driver is defined. When enabled,
+	  the PSCI driver is always probed and binds dirvers registered to the Arm SMCCC
+	  services if any and reported as supported by the SMCCC firmware.
+
 source "drivers/firmware/scmi/Kconfig"

drivers/firmware/psci.c

@@ -11,9 +11,11 @@
 #include <dm.h>
 #include <efi_loader.h>
 #include <irq_func.h>
+#include <linker_lists.h>
 #include <log.h>
 #include <sysreset.h>
 #include <asm/system.h>
+#include <dm/device-internal.h>
 #include <dm/lists.h>
 #include <linux/arm-smccc.h>
 #include <linux/delay.h>
@@ -95,6 +97,76 @@ static bool psci_is_system_reset2_supported(void)
 	return false;
 }
 
+static void smccc_invoke_hvc(unsigned long a0, unsigned long a1,
+			     unsigned long a2, unsigned long a3,
+			     unsigned long a4, unsigned long a5,
+			     unsigned long a6, unsigned long a7,
+			     struct arm_smccc_res *res)
+{
+	arm_smccc_hvc(a0, a1, a2, a3, a4, a5, a6, a7, res);
+}
+
+static void smccc_invoke_smc(unsigned long a0, unsigned long a1,
+			     unsigned long a2, unsigned long a3,
+			     unsigned long a4, unsigned long a5,
+			     unsigned long a6, unsigned long a7,
+			     struct arm_smccc_res *res)
+{
+	arm_smccc_smc(a0, a1, a2, a3, a4, a5, a6, a7, res);
+}
+
+static int bind_smccc_features(struct udevice *dev, int psci_method)
+{
+	struct psci_plat_data *pdata = dev_get_plat(dev);
+	struct arm_smccc_feature *feature;
+	size_t feature_cnt, n;
+
+	if (!IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES))
+		return 0;
+
+	/*
+	 * SMCCC features discovery invoke SMCCC standard function ID
+	 * ARM_SMCCC_ARCH_FEATURES but this sequence requires that this
+	 * standard ARM_SMCCC_ARCH_FEATURES function ID itself is supported.
+	 * It is queried here with invoking PSCI_FEATURES known available
+	 * from PSCI 1.0.
+	 */
+	if (!device_is_compatible(dev, "arm,psci-1.0") ||
+	    PSCI_VERSION_MAJOR(psci_0_2_get_version()) == 0)
+		return 0;
+
+	if (request_psci_features(ARM_SMCCC_ARCH_FEATURES) ==
+	    PSCI_RET_NOT_SUPPORTED)
+		return 0;
+
+	if (psci_method == PSCI_METHOD_HVC)
+		pdata->invoke_fn = smccc_invoke_hvc;
+	else
+		pdata->invoke_fn = smccc_invoke_smc;
+
+	feature_cnt = ll_entry_count(struct arm_smccc_feature, arm_smccc_feature);
+	feature = ll_entry_start(struct arm_smccc_feature, arm_smccc_feature);
+
+	for (n = 0; n < feature_cnt; n++, feature++) {
+		const char *drv_name = feature->driver_name;
+		struct udevice *dev2;
+		int ret;
+
+		if (!feature->is_supported || !feature->is_supported(pdata->invoke_fn))
+			continue;
+
+		ret = device_bind_driver(dev, drv_name, drv_name, &dev2);
+		if (ret) {
+			pr_warn("%s was not bound: %d, ignore\n", drv_name, ret);
+			continue;
+		}
+
+		dev_set_parent_plat(dev2, dev_get_plat(dev));
+	}
+
+	return 0;
+}
+
 static int psci_bind(struct udevice *dev)
 {
 	/* No SYSTEM_RESET support for PSCI 0.1 */
@@ -109,6 +181,10 @@ static int psci_bind(struct udevice *dev)
 			pr_debug("PSCI System Reset was not bound.\n");
 	}
 
+	/* From PSCI v1.0 onward we can discover services through ARM_SMCCC_FEATURE */
+	if (IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES) && device_is_compatible(dev, "arm,psci-1.0"))
+		dev_or_flags(dev, DM_FLAG_PROBE_AFTER_BIND);
+
 	return 0;
 }
 
@@ -136,7 +212,7 @@ static int psci_probe(struct udevice *dev)
 		return -EINVAL;
 	}
 
-	return 0;
+	return bind_smccc_features(dev, psci_method);
 }
 
 /**
@@ -240,4 +316,7 @@ U_BOOT_DRIVER(psci) = {
 	.of_match = psci_of_match,
 	.bind = psci_bind,
 	.probe = psci_probe,
+#ifdef CONFIG_ARM_SMCCC_FEATURES
+	.plat_auto = sizeof(struct psci_plat_data),
+#endif
 };

include/linux/arm-smccc.h

@@ -83,6 +83,22 @@ struct arm_smccc_quirk {
 	} state;
 };
 
+/**
+ * struct arm_smccc_feature - Driver registration data for discoverable feature
+ * @driver_name: name of the driver relate to the SMCCC feature
+ * @is_supported: callback to test if SMCCC feature is supported
+ */
+struct arm_smccc_feature {
+	const char *driver_name;
+	bool (*is_supported)(void (*invoke_fn)(unsigned long a0, unsigned long a1, unsigned long a2,
+					       unsigned long a3, unsigned long a4, unsigned long a5,
+					       unsigned long a6, unsigned long a7,
+					       struct arm_smccc_res *res));
+};
+
+#define ARM_SMCCC_FEATURE_DRIVER(__name) \
+	ll_entry_declare(struct arm_smccc_feature, __name, arm_smccc_feature)
+
 /**
  * __arm_smccc_smc() - make SMC calls
  * @a0-a7: arguments passed in registers 0 to 7

include/linux/psci.h

@@ -11,6 +11,8 @@
 #ifndef _UAPI_LINUX_PSCI_H
 #define _UAPI_LINUX_PSCI_H
 
+#include <linux/arm-smccc.h>
+
 /*
  * PSCI v0.1 interface
  *
@@ -115,6 +117,18 @@
 #define PSCI_RET_DISABLED			-8
 #define PSCI_RET_INVALID_ADDRESS		-9
 
+/**
+ * struct psci_plat_data - PSCI driver platform data
+ * @method: Selected invocation conduit
+ */
+struct psci_plat_data {
+	void (*invoke_fn)(unsigned long arg0, unsigned long arg1,
+			  unsigned long arg2, unsigned long arg3,
+			  unsigned long arg4, unsigned long arg5,
+			  unsigned long arg6, unsigned long arg7,
+			  struct arm_smccc_res *res);
+};
+
 #ifdef CONFIG_ARM_PSCI_FW
 unsigned long invoke_psci_fn(unsigned long a0, unsigned long a1,
 			     unsigned long a2, unsigned long a3);