On Thu, Nov 07, 2024 at 03:38:27PM -0800, Elliot Berman wrote:
> 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.
>
> A separate initcall is needed to parse the devicetree, instead of using
> psci_dt_init because mm isn't sufficiently set up to allocate memory.
Nit: information below this point is more a cover letter than for the
commit log.
> 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.
>
> Tested-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> ---
> drivers/firmware/psci/psci.c | 104 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 104 insertions(+)
>
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 2328ca58bba61fdb677ac20a1a7447882cd0cf22..e60e3f8749c5a6732c51d23a2c1f453361132d9a 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -79,6 +79,14 @@ 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 __ro_after_init;
> +static size_t num_psci_reset_params __ro_after_init;
> +
> static inline bool psci_has_ext_power_state(void)
> {
> return psci_cpu_suspend_feature &
> @@ -305,9 +313,38 @@ static int get_set_conduit_method(const struct device_node *np)
> return 0;
> }
>
> +static void psci_vendor_system_reset2(const char *cmd)
> +{
> + 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);
> + /*
> + * if vendor reset fails, log it and fall back to
> + * architecture reset types
> + */
> + pr_err("failed to perform reset \"%s\": %ld\n", cmd,
> + (long)ret);
> + return;
> + }
> + }
> +}
> +
> static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> void *data)
> {
> + /*
> + * try to do the vendor system_reset2
> + * If the reset fails or there wasn't a match on the command,
> + * fall back to architectural resets
> + */
> + if (data && num_psci_reset_params)
> + psci_vendor_system_reset2(data);
> +
> if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> psci_system_reset2_supported) {
This is a mess. To issue architectural warm reset we check reboot_mode,
for vendor resets we ignore it - there is no rationale, that's the point
I am making.
Also see my question on the other thread re: user space and reset
"modes".
I appreciate we are not making progress but I don't want to pick up
the pieces later after merging this code - it is unclear to me what's
the best path forward - I would like to understand how other
platforms/arches behave in this respect.
> /*
> @@ -750,6 +787,73 @@ static const struct of_device_id psci_of_match[] __initconst = {
> {},
> };
>
> +#define REBOOT_PREFIX "mode-"
> +
> +static int __init psci_init_system_reset2_modes(void)
> +{
> + const size_t len = strlen(REBOOT_PREFIX);
> + struct psci_reset_param *param;
> + struct device_node *psci_np __free(device_node) = NULL;
> + struct device_node *np __free(device_node) = NULL;
> + struct property *prop;
> + size_t count = 0;
> + u32 magic[2];
> + int num;
> +
> + if (!psci_system_reset2_supported)
> + return 0;
> +
> + psci_np = of_find_matching_node(NULL, psci_of_match);
> + if (!psci_np)
> + return 0;
> +
> + np = of_find_node_by_name(psci_np, "reset-types");
> + if (!np)
> + return 0;
> +
> + for_each_property_of_node(np, prop) {
> + if (strncmp(prop->name, REBOOT_PREFIX, len))
> + continue;
> + num = of_property_count_u32_elems(np, prop->name);
> + if (num != 1 && num != 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);
FWIW - I think you need to keep the logic in the previous loop into account
because that's what is used to allocate param, it is not a given that
param is valid at this stage if I am not mistaken - the previous loop
checked:
num = of_property_count_u32_elems(np, prop->name);
if (num != 1 && num != 2)
continue;
Lorenzo
> + if (!param->mode)
> + continue;
> +
> + num = of_property_read_variable_u32_array(np, prop->name, magic,
> + 1, ARRAY_SIZE(magic));
> + 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 > 1 ? 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;
>
> --
> 2.34.1
>
