[PATCH v2 3/4] firmware: psci: Read and use vendor reset types

Elliot Berman
2024-04-14T19:32:02Z

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@quicinc.com>
---
drivers/firmware/psci/psci.c | 90 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 90 insertions(+)

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index d9629ff87861..e0a764743a20 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 &
@@ -305,9 +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;
+ unsigned long ret;
+ size_t i;
+
+ for (i = 0; i < num_psci_reset_params; i++) {
+ if (!strcmp(psci_reset_params[i].mode, cmd)) {
+ ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
+ psci_reset_params[i].reset_type,
+ psci_reset_params[i].cookie, 0);
+ pr_err("failed to perform reset \"%s\": %ld\n",
+ cmd, (long)ret);
+ }
+ }
+}
+
static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
void *data)
{
+ if (data && num_psci_reset_params)
+ psci_vendor_sys_reset2(action, data);
+
if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
psci_system_reset2_supported) {
/*
@@ -748,6 +778,66 @@ 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 num;
+
+ 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;
+ num = of_property_count_elems_of_size(np, prop->name, sizeof(magic[0]));
+ if (num != 1 && num != 2)
+ continue;
+
+ count++;
+ }
+
+ param = psci_reset_params = kcalloc(count, sizeof(*psci_reset_params), GFP_KERNEL);
+ if (!psci_reset_params) {
+ of_node_put(np);
+ 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;
+
+ num = of_property_read_variable_u32_array(np, prop->name, magic, 1, 2);
+ if (num < 0) {
+ pr_warn("Failed to parse vendor reboot mode %s\n", param->mode);
+ kfree_const(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 = num == 2 ? magic[1] : 0;
+ param++;
+ num_psci_reset_params++;
+ }
+
+ of_node_put(np);
+ return 0;
+}
+arch_initcall(psci_init_system_reset2_modes);
+
int __init psci_dt_init(void)
{
struct device_node *np;

--
2.34.1