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Subject[RFC PATCH 5/9] dt: deps: register drivers based on the initialization order based on DT
Date
The init system currently calls unknown functions with almost unknown
functionality in an almost random order.

Fixing this is on a short-term basis is a bit tricky.

In order to register drivers with a deterministic order, a list of all
available in-kernel drivers is needed. Unfortunately such a list doesn't
exist, just a list of initcalls does exist.

The trick now is to first call special annotated initcalls (I call those
"well done") for platform drivers, but not actualy starting those drivers
by calling their probe function, but just collectiong their meta datas
(struct platform_driver). After all those informations were collected,
available the drivers will be started according to the previously
determined order.

The annotation of such platform drivers is necessary because it must be
made sure that those drivers don't care if the probe is actually called in
their initcall or later.

That means that all platform drivers which already do use

module_platform_driver() or
module_platform_driver_probe()

don't need any modification because their initcall is known and already well
done. But all platform drivers which do use

module_init() or
*_initcall()

have to be reviewed if they are "well done". If they are, they need a change
like

-module_init(foo_init);
+well_done_platform_module_init(foo_init);

or

-subsys_initcall(foo_init);
+well_done_platform_initcall(subsys, foo_init);

to become included in the deterministic order in which platform drivers
will be initialized.

All other platform drivers will still be initialized in random order before
platform drivers included in the deterministic order will be initialized.
"Well done" drivers which don't appear in the order (because they don't appear
in the DT) will be initialized after those which do appear in the order.

If CONFIG_OF_DEPENDENCIES is disabled, nothing is changed at all.

The long range target to fix the problem should be to include a list (array)
of struct platform_driver in the kernel for all in-kernel platform drivers,
instead of just initcalls. This will be easy if all platform drivers have
become "well done".

Unfortunately there are some drivers which will need quiet some changes
to become "well done". As an example for such an initcall look e.g. at
drivers/tty/serial/8250/8250_core.c.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
---
drivers/base/platform.c | 13 +++++++
drivers/of/of_dependencies.c | 79 +++++++++++++++++++++++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 1 +
include/linux/init.h | 19 ++++++++++
include/linux/of_dependencies.h | 5 +++
include/linux/platform_device.h | 16 ++++++--
init/main.c | 17 ++++++++-
7 files changed, 145 insertions(+), 5 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index bc78848..b9c9b33 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -13,6 +13,7 @@
#include <linux/string.h>
#include <linux/platform_device.h>
#include <linux/of_device.h>
+#include <linux/of_dependencies.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/dma-mapping.h>
@@ -541,6 +542,12 @@ int __platform_driver_register(struct platform_driver *drv,
if (drv->shutdown)
drv->driver.shutdown = platform_drv_shutdown;

+#ifdef CONFIG_OF_DEPENDENCIES
+ if (of_init_is_recording())
+ /* Just record the driver */
+ return of_init_register_platform_driver(drv);
+ else
+#endif
return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(__platform_driver_register);
@@ -590,8 +597,14 @@ int __init_or_module platform_driver_probe(struct platform_driver *drv,

/* temporary section violation during probe() */
drv->probe = probe;
+
retval = code = platform_driver_register(drv);

+#ifdef CONFIG_OF_DEPENDENCIES
+ if (of_init_is_recording())
+ /* Just record the driver */
+ return retval;
+#endif
/*
* Fixup that section violation, being paranoid about code scanning
* the list of drivers in order to probe new devices. Check to see
diff --git a/drivers/of/of_dependencies.c b/drivers/of/of_dependencies.c
index 7905172..4af62d5 100644
--- a/drivers/of/of_dependencies.c
+++ b/drivers/of/of_dependencies.c
@@ -46,9 +46,12 @@ struct init_order {
/* Used to keep track of parent devices in regard to the DT */
uint32_t parent_by_phandle[MAX_DT_NODES+1];
struct device *device_by_phandle[MAX_DT_NODES+1];
+ struct platform_driver *platform_drivers[MAX_DT_NODES+1];
+ unsigned count_drivers;
};
static struct init_order order __initdata;

+static bool is_recording;

/* Copied from drivers/of/base.c (because it's lockless). */
static struct property * __init __of_find_property(const struct device_node *np,
@@ -401,3 +404,79 @@ void __init of_init_free_order(void)
order.count = 0;
/* remove_new_phandles(); */
}
+
+void __init of_init_set_recording(bool recording)
+{
+ is_recording = recording;
+}
+
+bool of_init_is_recording(void)
+{
+ return is_recording;
+}
+
+int of_init_register_platform_driver(struct platform_driver *drv)
+{
+ BUG_ON(!is_recording);
+ order.platform_drivers[order.count_drivers++] = drv;
+ return 0;
+}
+
+void __init of_init_register_drivers(void)
+{
+ unsigned i, j;
+ int rc __maybe_unused;
+
+ BUG_ON(is_recording);
+ /*
+ * Because we already have a list of devices and drivers together
+ * with their compatible strings, the below code could be speed up
+ * by replacing the functions which are walking through lists with
+ * something which uses trees or hashes to compare/search strings.
+ * These are of_driver_match_device() and driver_find() (the latter
+ * is called again in driver_register().
+ */
+ for (i = 0; i < order.count; ++i) {
+ struct device_node *node = order.order[i];
+ struct device *dev = order.device_by_phandle[node->phandle];
+
+ for (j = 0; j < order.count_drivers; ++j) {
+ struct platform_driver *drv = order.platform_drivers[j];
+
+ if (of_driver_match_device(dev, &drv->driver)) {
+ if (!driver_find(drv->driver.name,
+ drv->driver.bus))
+ platform_driver_register(drv);
+ if (dev->parent)
+ device_lock(dev->parent);
+ rc = device_attach(dev);
+ if (dev->parent)
+ device_unlock(dev->parent);
+ break;
+ }
+ }
+ if (j >= order.count_drivers) {
+ /*
+ * No driver in the initialization order matched,
+ * try to attach the device, maybe a driver already
+ * exists (e.g. loaded pre-smp).
+ */
+ if (dev->parent)
+ device_lock(dev->parent);
+ rc = device_attach(dev);
+ if (dev->parent)
+ device_unlock(dev->parent);
+ }
+ }
+ /*
+ * Now just register all drivers, including those not used through
+ * the initialization order (well-done drivers which aren't listed
+ * in the DT or blacklisted through of_init_create_devices()).
+ */
+ for (j = 0; j < order.count_drivers; ++j) {
+ struct platform_driver *drv = order.platform_drivers[j];
+
+ if (!driver_find(drv->driver.name, drv->driver.bus))
+ platform_driver_register(drv);
+ }
+}
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bc2121f..cedb3b0 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -633,6 +633,7 @@
INIT_CALLS_LEVEL(rootfs) \
INIT_CALLS_LEVEL(6) \
INIT_CALLS_LEVEL(7) \
+ INIT_CALLS_LEVEL(8) \
VMLINUX_SYMBOL(__initcall_end) = .;

#define CON_INITCALL \
diff --git a/include/linux/init.h b/include/linux/init.h
index e168880..acb7dfa 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -209,6 +209,23 @@ extern bool initcall_debug;
#define late_initcall(fn) __define_initcall(fn, 7)
#define late_initcall_sync(fn) __define_initcall(fn, 7s)

+/*
+ * A well_done_platform_module_init or well_done_platform_initcall
+ * only calls platform_driver_register() or platform_driver_probe()
+ * and ignores the return code. This is necessary because the
+ * actual calls to platform_driver_register() or platform_driver_probe()
+ * will be delayed when CONFIG_OF_DEPENDENCIES is enabled. This is done
+ * to sort those calls based on the dependencies in the DT (matched to the
+ * platform driver data).
+ */
+#ifdef CONFIG_OF_DEPENDENCIES
+#define well_done_platform_module_init(fn) __define_initcall(fn, 8)
+#define well_done_platform_initcall(leve, fn) __define_initcall(fn, 8)
+#else
+#define well_done_platform_module_init(fn) module_init(fn)
+#define well_done_platform_initcall(level, fn) level ## _initcall(fn)
+#endif
+
#define __initcall(fn) device_initcall(fn)

#define __exitcall(fn) \
@@ -289,6 +306,8 @@ void __init parse_early_options(char *cmdline);
#define rootfs_initcall(fn) module_init(fn)
#define device_initcall(fn) module_init(fn)
#define late_initcall(fn) module_init(fn)
+#define well_done_platform_initcall(fn) module_init(fn)
+#define well_done_platform_module_init(fn) module_init(fn)

#define console_initcall(fn) module_init(fn)
#define security_initcall(fn) module_init(fn)
diff --git a/include/linux/of_dependencies.h b/include/linux/of_dependencies.h
index e046ce2..8869162 100644
--- a/include/linux/of_dependencies.h
+++ b/include/linux/of_dependencies.h
@@ -58,4 +58,9 @@ extern void of_init_create_devices(const struct of_device_id *matches,
*/
extern void of_init_free_order(void);

+void of_init_set_recording(bool recording);
+bool of_init_is_recording(void);
+int of_init_register_platform_driver(struct platform_driver *drv);
+void of_init_register_drivers(void);
+
#endif /* _LINUX_OF_DEPENDENCIES_H */
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 16f6654..b8559d9 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -215,9 +215,17 @@ static inline void platform_set_drvdata(struct platform_device *pdev,
* boilerplate. Each module may only use this macro once, and
* calling it replaces module_init() and module_exit()
*/
-#define module_platform_driver(__platform_driver) \
- module_driver(__platform_driver, platform_driver_register, \
- platform_driver_unregister)
+#define module_platform_driver(__driver) \
+static int __init __driver##_init(void) \
+{ \
+ return platform_driver_register(&(__driver)); \
+} \
+well_done_platform_module_init(__driver##_init); \
+static void __exit __driver##_exit(void) \
+{ \
+ platform_driver_unregister(&(__driver)); \
+} \
+module_exit(__driver##_exit);

/* module_platform_driver_probe() - Helper macro for drivers that don't do
* anything special in module init/exit. This eliminates a lot of
@@ -230,7 +238,7 @@ static int __init __platform_driver##_init(void) \
return platform_driver_probe(&(__platform_driver), \
__platform_probe); \
} \
-module_init(__platform_driver##_init); \
+well_done_platform_module_init(__platform_driver##_init); \
static void __exit __platform_driver##_exit(void) \
{ \
platform_driver_unregister(&(__platform_driver)); \
diff --git a/init/main.c b/init/main.c
index 9c7fd4c..7591cd1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -77,6 +77,7 @@
#include <linux/sched_clock.h>
#include <linux/context_tracking.h>
#include <linux/random.h>
+#include <linux/of_dependencies.h>

#include <asm/io.h>
#include <asm/bugs.h>
@@ -720,6 +721,7 @@ extern initcall_t __initcall4_start[];
extern initcall_t __initcall5_start[];
extern initcall_t __initcall6_start[];
extern initcall_t __initcall7_start[];
+extern initcall_t __initcall8_start[];
extern initcall_t __initcall_end[];

static initcall_t *initcall_levels[] __initdata = {
@@ -731,6 +733,7 @@ static initcall_t *initcall_levels[] __initdata = {
__initcall5_start,
__initcall6_start,
__initcall7_start,
+ __initcall8_start,
__initcall_end,
};

@@ -744,6 +747,8 @@ static char *initcall_level_names[] __initdata = {
"fs",
"device",
"late",
+ /* must be the last level to become excluded in do_initcalls() */
+ "well-done-platform-driver",
};

static void __init do_initcall_level(int level)
@@ -766,7 +771,7 @@ static void __init do_initcalls(void)
{
int level;

- for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)
+ for (level = 0; level < ARRAY_SIZE(initcall_levels) - 3; level++)
do_initcall_level(level);
}

@@ -787,6 +792,16 @@ static void __init do_basic_setup(void)
do_ctors();
usermodehelper_enable();
do_initcalls();
+#ifdef CONFIG_OF_DEPENDENCIES
+ /* collect a list of available platform drivers */
+ of_init_set_recording(true);
+ do_initcall_level(ARRAY_SIZE(initcall_levels) - 2);
+ of_init_set_recording(false);
+ /* probe available platform drivers with deterministic order */
+ of_init_register_drivers();
+ /* register late drivers */
+ do_initcall_level(ARRAY_SIZE(initcall_levels) - 3);
+#endif
random_int_secret_init();
}

--
1.8.3.1


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