[PATCH 3/3] firmware: psci: Read and use vendor reset types

[Elliot Berman]

SoC vendors have different types of resets and are controlled through
various registers. For instance, Qualcomm chipsets can reboot to a
"download mode" that allows a RAM dump to be collected. Another example
is they also support writing a cookie that can be read by bootloader
during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these
vendor reset types to be implemented without requiring drivers for every
register/cookie.

Add support in PSCI to statically map reboot mode commands from
userspace to a vendor reset and cookie value using the device tree.

Reboot mode framework is close but doesn't quite fit with the
design and requirements for PSCI SYSTEM_RESET2. Some of these issues can
be solved but doesn't seem reasonable in sum:
 1. reboot mode registers against the reboot_notifier_list, which is too
    early to call SYSTEM_RESET2. PSCI would need to remember the reset
    type from the reboot-mode framework callback and use it
    psci_sys_reset.
 2. reboot mode assumes only one cookie/parameter is described in the
    device tree. SYSTEM_RESET2 uses 2: one for the type and one for
    cookie.
 3. psci cpuidle driver already registers a driver against the
    arm,psci-1.0 compatible. Refactoring would be needed to have both a
    cpuidle and reboot-mode driver.

Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
 drivers/firmware/psci/psci.c | 87 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index d9629ff87861..3f6a862c3999 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -29,6 +29,8 @@
 #include <asm/smp_plat.h>
 #include <asm/suspend.h>
 
+#define REBOOT_PREFIX "mode-"
+
 /*
  * While a 64-bit OS can make calls with SMC32 calling conventions, for some
  * calls it is necessary to use SMC64 to pass or return 64-bit values.
@@ -79,6 +81,14 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
 static u32 psci_cpu_suspend_feature;
 static bool psci_system_reset2_supported;
 
+struct psci_reset_param {
+	const char *mode;
+	u32 reset_type;
+	u32 cookie;
+};
+static struct psci_reset_param *psci_reset_params;
+static size_t num_psci_reset_params;
+
 static inline bool psci_has_ext_power_state(void)
 {
 	return psci_cpu_suspend_feature &
@@ -305,11 +315,29 @@ static int get_set_conduit_method(const struct device_node *np)
 	return 0;
 }
 
+static void psci_vendor_sys_reset2(unsigned long action, void *data)
+{
+	const char *cmd = data;
+	size_t i;
+
+	for (i = 0; i < num_psci_reset_params; i++) {
+		if (!strcmp(psci_reset_params[i].mode, cmd)) {
+			invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
+				       psci_reset_params[i].reset_type,
+				       psci_reset_params[i].cookie, 0);
+			break;
+		}
+	}
+}
+
 static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
 			  void *data)
 {
+	if (psci_system_reset2_supported && num_psci_reset_params)
+		psci_vendor_sys_reset2(action, data);
+
 	if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
-	    psci_system_reset2_supported) {
+		 psci_system_reset2_supported) {
 		/*
 		 * reset_type[31] = 0 (architectural)
 		 * reset_type[30:0] = 0 (SYSTEM_WARM_RESET)
@@ -748,6 +776,63 @@ static const struct of_device_id psci_of_match[] __initconst = {
 	{},
 };
 
+static int __init psci_init_system_reset2_modes(void)
+{
+	const size_t len = strlen(REBOOT_PREFIX);
+	struct psci_reset_param *param;
+	struct device_node *np;
+	struct property *prop;
+	size_t count = 0;
+	u32 magic[2];
+	int ret;
+
+	if (!psci_system_reset2_supported)
+		return 0;
+
+	np = of_find_matching_node(NULL, psci_of_match);
+	if (!np)
+		return 0;
+
+	for_each_property_of_node(np, prop) {
+		if (strncmp(prop->name, REBOOT_PREFIX, len))
+			continue;
+		ret = of_property_count_elems_of_size(np, prop->name, sizeof(magic[0]));
+		if (ret != 1 && ret != 2)
+			continue;
+
+		count++;
+	}
+
+	param = psci_reset_params = kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
+	if (!psci_reset_params)
+		return -ENOMEM;
+
+	for_each_property_of_node(np, prop) {
+		if (strncmp(prop->name, REBOOT_PREFIX, len))
+			continue;
+
+		param->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
+		if (!param->mode)
+			continue;
+
+		ret = of_property_read_variable_u32_array(np, prop->name, magic, 1, 2);
+		if (ret < 0) {
+			pr_warn("Failed to parse vendor reboot mode %s\n", param->mode);
+			kfree(param->mode);
+			continue;
+		}
+
+		/* Force reset type to be in vendor space */
+		param->reset_type = PSCI_1_1_RESET_TYPE_VENDOR_START | magic[0];
+		param->cookie = ret == 2 ? magic[1] : 0;
+		param++;
+		num_psci_reset_params++;
+	}
+
+	return 0;
+}
+arch_initcall(psci_init_system_reset2_modes);
+
 int __init psci_dt_init(void)
 {
 	struct device_node *np;

-- 
2.41.0