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kernel: Device deferred initialization

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Currently, all devices are initialized at boot time (following their
level and priority order). This patch introduces deferred
initialization: by setting the property `zephyr,deferred-init` on a
device on the devicetree, Zephyr will not initialized the device.

To initialize such devices, one has to call `device_init()`.

Deferred initialization is done by grouping all deferred devices on a
different ELF section. In this way, there's no need to consume more
memory to keep track of deferred devices. When `device_init()` is
called, Zephyr will scan the deferred devices section and call the
initialization function for the matching device. As this scanning is
done only during deferred device initialization, its cost should be
bearable.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>
This commit is contained in:
Ederson de Souza 2024-01-05 13:29:20 -08:00 • committed by Anas Nashif
commit eeebb4d911
4 changed files with 111 additions and 25 deletions
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83
kernel/init.c
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@ -36,6 +36,7 @@
#include <zephyr/timing/timing.h>
#include <zephyr/logging/log.h>
#include <zephyr/pm/device_runtime.h>
#include <zephyr/internal/syscall_handler.h>
LOG_MODULE_REGISTER(os, CONFIG_KERNEL_LOG_LEVEL);
BUILD_ASSERT(CONFIG_MP_NUM_CPUS == CONFIG_MP_MAX_NUM_CPUS,
@ -301,6 +302,37 @@ extern volatile uintptr_t __stack_chk_guard;
__pinned_bss
bool z_sys_post_kernel;
static int do_device_init(const struct init_entry *entry)
{
const struct device *dev = entry->dev;
int rc = 0;
if (entry->init_fn.dev != NULL) {
rc = entry->init_fn.dev(dev);
/* Mark device initialized. If initialization
* failed, record the error condition.
*/
if (rc != 0) {
if (rc < 0) {
rc = -rc;
}
if (rc > UINT8_MAX) {
rc = UINT8_MAX;
}
dev->state->init_res = rc;
}
}
dev->state->initialized = true;
if (rc == 0) {
/* Run automatic device runtime enablement */
(void)pm_device_runtime_auto_enable(dev);
}
return rc;
}
/**
* @brief Execute all the init entry initialization functions at a given level
*
@ -332,36 +364,39 @@ static void z_sys_init_run_level(enum init_level level)
const struct device *dev = entry->dev;
if (dev != NULL) {
int rc = 0;
if (entry->init_fn.dev != NULL) {
rc = entry->init_fn.dev(dev);
/* Mark device initialized. If initialization
* failed, record the error condition.
*/
if (rc != 0) {
if (rc < 0) {
rc = -rc;
}
if (rc > UINT8_MAX) {
rc = UINT8_MAX;
}
dev->state->init_res = rc;
}
}
dev->state->initialized = true;
if (rc == 0) {
/* Run automatic device runtime enablement */
(void)pm_device_runtime_auto_enable(dev);
}
do_device_init(entry);
} else {
(void)entry->init_fn.sys();
}
}
}
int z_impl_device_init(const struct device *dev)
{
if (dev == NULL) {
return -ENOENT;
}
STRUCT_SECTION_FOREACH_ALTERNATE(_deferred_init, init_entry, entry) {
if (entry->dev == dev) {
return do_device_init(entry);
}
}
return -ENOENT;
}
#ifdef CONFIG_USERSPACE
static inline int z_vrfy_device_init(const struct device *dev)
{
K_OOPS(K_SYSCALL_OBJ_INIT(dev, K_OBJ_ANY));
return z_impl_device_init(dev);
}
#include <syscalls/device_init_mrsh.c>
#endif
extern void boot_banner(void);