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Subject[PATCH V3 7/8] drivers: boot_constraint: Manage deferrable constraints
Date
It is possible that some of the resources aren't available at the time
constraints are getting set and the boot constraints core will return
-EPROBE_DEFER for them. In order to retry adding the constraints at a
later point of time (after the resource is added and before any of its
users come up), this patch proposes two things:

- Each constraint is represented by a virtual platform device, so that
it is re-probed again until the time all the dependencies aren't met.
The platform device is removed along with the constraint, with help of
the free_resources() callback.

- Enable early defer probing support by calling
driver_enable_deferred_probe(), so that the core retries probing
deferred devices every time any device is bound to a driver. This
makes sure that the constraint is set before any of the users of the
resources come up.

This is tested on ARM64 Hikey board where probe was deferred for a
device.

Tested-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/base/base.h | 1 +
drivers/base/boot_constraints/Makefile | 2 +-
drivers/base/boot_constraints/core.c | 2 +-
drivers/base/boot_constraints/core.h | 2 +
drivers/base/boot_constraints/deferrable_dev.c | 192 +++++++++++++++++++++++++
drivers/base/dd.c | 12 ++
include/linux/boot_constraint.h | 10 ++
7 files changed, 219 insertions(+), 2 deletions(-)
create mode 100644 drivers/base/boot_constraints/deferrable_dev.c

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 539432a14b5c..9c117f0dc44c 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -131,6 +131,7 @@ extern char *make_class_name(const char *name, struct kobject *kobj);
extern int devres_release_all(struct device *dev);
extern void device_block_probing(void);
extern void device_unblock_probing(void);
+extern void driver_enable_deferred_probe(void);

/* /sys/devices directory */
extern struct kset *devices_kset;
diff --git a/drivers/base/boot_constraints/Makefile b/drivers/base/boot_constraints/Makefile
index b7ade1a7afb5..a765094623a3 100644
--- a/drivers/base/boot_constraints/Makefile
+++ b/drivers/base/boot_constraints/Makefile
@@ -1,3 +1,3 @@
# Makefile for device boot constraints

-obj-y := clk.o core.o pm.o supply.o
+obj-y := clk.o deferrable_dev.o core.o pm.o supply.o
diff --git a/drivers/base/boot_constraints/core.c b/drivers/base/boot_constraints/core.c
index c0e3a85ff85a..8e2f9b8fe80f 100644
--- a/drivers/base/boot_constraints/core.c
+++ b/drivers/base/boot_constraints/core.c
@@ -24,7 +24,7 @@
static LIST_HEAD(constraint_devices);
static DEFINE_MUTEX(constraint_devices_mutex);

-static bool boot_constraints_disabled;
+bool boot_constraints_disabled;

static int __init constraints_disable(char *str)
{
diff --git a/drivers/base/boot_constraints/core.h b/drivers/base/boot_constraints/core.h
index ee84e237c66a..41354f7206bf 100644
--- a/drivers/base/boot_constraints/core.h
+++ b/drivers/base/boot_constraints/core.h
@@ -32,6 +32,8 @@ struct constraint {
void *private;
};

+extern bool boot_constraints_disabled;
+
void constraint_add_debugfs(struct constraint *constraint, const char *suffix);
void constraint_remove_debugfs(struct constraint *constraint);

diff --git a/drivers/base/boot_constraints/deferrable_dev.c b/drivers/base/boot_constraints/deferrable_dev.c
new file mode 100644
index 000000000000..5169882f2af1
--- /dev/null
+++ b/drivers/base/boot_constraints/deferrable_dev.c
@@ -0,0 +1,192 @@
+/*
+ * Copyright (C) 2017 Linaro.
+ * Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#define pr_fmt(fmt) "Boot Constraints: " fmt
+
+#include <linux/err.h>
+#include <linux/idr.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include "../base.h"
+#include "core.h"
+
+static DEFINE_IDA(pdev_index);
+
+struct boot_constraint_pdata {
+ struct device *dev;
+ struct dev_boot_constraint constraint;
+ int probe_failed;
+ int index;
+};
+
+static void boot_constraint_remove(void *data)
+{
+ struct platform_device *pdev = data;
+ struct boot_constraint_pdata *pdata = dev_get_platdata(&pdev->dev);
+
+ ida_simple_remove(&pdev_index, pdata->index);
+ kfree(pdata->constraint.data);
+ platform_device_unregister(pdev);
+}
+
+/*
+ * A platform device is added for each and every constraint, to handle
+ * -EPROBE_DEFER properly.
+ */
+static int boot_constraint_probe(struct platform_device *pdev)
+{
+ struct boot_constraint_pdata *pdata = dev_get_platdata(&pdev->dev);
+ struct dev_boot_constraint_info info;
+ int ret;
+
+ if (WARN_ON(!pdata))
+ return -EINVAL;
+
+ info.constraint = pdata->constraint;
+ info.free_resources = boot_constraint_remove;
+ info.free_resources_data = pdev;
+
+ ret = dev_boot_constraint_add(pdata->dev, &info);
+ if (ret) {
+ if (ret == -EPROBE_DEFER)
+ driver_enable_deferred_probe();
+ else
+ pdata->probe_failed = ret;
+ }
+
+ return ret;
+}
+
+static struct platform_driver boot_constraint_driver = {
+ .driver = {
+ .name = "boot-constraints-dev",
+ },
+ .probe = boot_constraint_probe,
+};
+
+static int __init boot_constraint_init(void)
+{
+ return platform_driver_register(&boot_constraint_driver);
+}
+core_initcall(boot_constraint_init);
+
+static int _boot_constraint_add_dev(struct device *dev,
+ struct dev_boot_constraint *constraint)
+{
+ struct boot_constraint_pdata pdata = {
+ .dev = dev,
+ .constraint.type = constraint->type,
+ };
+ struct platform_device *pdev;
+ struct boot_constraint_pdata *pdev_pdata;
+ int size, ret;
+
+ switch (constraint->type) {
+ case DEV_BOOT_CONSTRAINT_CLK:
+ size = sizeof(struct dev_boot_constraint_clk_info);
+ break;
+ case DEV_BOOT_CONSTRAINT_PM:
+ size = 0;
+ break;
+ case DEV_BOOT_CONSTRAINT_SUPPLY:
+ size = sizeof(struct dev_boot_constraint_supply_info);
+ break;
+ default:
+ dev_err(dev, "%s: Constraint type (%d) not supported\n",
+ __func__, constraint->type);
+ return -EINVAL;
+ }
+
+ /* Will be freed from boot_constraint_remove() */
+ pdata.constraint.data = kmemdup(constraint->data, size, GFP_KERNEL);
+ if (!pdata.constraint.data)
+ return -ENOMEM;
+
+ ret = ida_simple_get(&pdev_index, 0, 256, GFP_KERNEL);
+ if (ret < 0) {
+ dev_err(dev, "failed to allocate index (%d)\n", ret);
+ goto free;
+ }
+
+ pdata.index = ret;
+
+ pdev = platform_device_register_data(NULL, "boot-constraints-dev", ret,
+ &pdata, sizeof(pdata));
+ if (IS_ERR(pdev)) {
+ dev_err(dev, "%s: Failed to create pdev (%ld)\n", __func__,
+ PTR_ERR(pdev));
+ ret = PTR_ERR(pdev);
+ goto ida_remove;
+ }
+
+ /* Release resources if probe has failed */
+ pdev_pdata = dev_get_platdata(&pdev->dev);
+ if (pdev_pdata->probe_failed) {
+ ret = pdev_pdata->probe_failed;
+ goto remove_pdev;
+ }
+
+ return 0;
+
+remove_pdev:
+ platform_device_unregister(pdev);
+ida_remove:
+ ida_simple_remove(&pdev_index, pdata.index);
+free:
+ kfree(pdata.constraint.data);
+
+ return ret;
+}
+
+int dev_boot_constraint_add_deferrable(struct device *dev,
+ struct dev_boot_constraint *constraints, int count)
+{
+ int ret, i;
+
+ if (boot_constraints_disabled)
+ return -ENODEV;
+
+ for (i = 0; i < count; i++) {
+ ret = _boot_constraint_add_dev(dev, &constraints[i]);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dev_boot_constraint_add_deferrable);
+
+/* This only creates platform devices for now */
+int dev_boot_constraint_add_of_deferrable(const char *compatible,
+ struct dev_boot_constraint *constraints, int count)
+{
+ struct platform_device *pdev;
+ struct device_node *np;
+
+ if (boot_constraints_disabled)
+ return -ENODEV;
+
+ np = of_find_compatible_node(NULL, NULL, compatible);
+ if (!np)
+ return -ENODEV;
+
+ pdev = of_find_device_by_node(np);
+ if (!pdev)
+ pdev = of_platform_device_create(np, NULL, NULL);
+
+ of_node_put(np);
+
+ if (!pdev)
+ return -ENODEV;
+
+ return dev_boot_constraint_add_deferrable(&pdev->dev, constraints,
+ count);
+}
+EXPORT_SYMBOL_GPL(dev_boot_constraint_add_of_deferrable);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 2262a4a4c0e4..62a8a22f8b04 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -204,6 +204,18 @@ void device_unblock_probing(void)
}

/**
+ * driver_enable_deferred_probe() - Enable probing of deferred devices
+ *
+ * We don't want to get in the way when the bulk of drivers are getting probed
+ * and so deferred probe is disabled in the beginning. Enable it now because we
+ * need it.
+ */
+void driver_enable_deferred_probe(void)
+{
+ driver_deferred_probe_enable = true;
+}
+
+/**
* deferred_probe_initcall() - Enable probing of deferred devices
*
* We don't want to get in the way when the bulk of drivers are getting probed.
diff --git a/include/linux/boot_constraint.h b/include/linux/boot_constraint.h
index edc9abe7913a..f66c2f6d14dc 100644
--- a/include/linux/boot_constraint.h
+++ b/include/linux/boot_constraint.h
@@ -47,12 +47,22 @@ struct dev_boot_constraint_info {
int dev_boot_constraint_add(struct device *dev,
struct dev_boot_constraint_info *info);
void dev_boot_constraints_remove(struct device *dev);
+int dev_boot_constraint_add_deferrable(struct device *dev,
+ struct dev_boot_constraint *constraints, int count);
+int dev_boot_constraint_add_of_deferrable(const char *compatible,
+ struct dev_boot_constraint *constraints, int count);
#else
static inline
int dev_boot_constraint_add(struct device *dev,
struct dev_boot_constraint_info *info);
{ return -EINVAL; }
static inline void dev_boot_constraints_remove(struct device *dev) {}
+static inline int dev_boot_constraint_add_deferrable(struct device *dev,
+ struct dev_boot_constraint *constraints, int count)
+{ return -EINVAL; }
+static inline int dev_boot_constraint_add_of_deferrable(const char *compatible,
+ struct dev_boot_constraint *constraints, int count)
+{ return -EINVAL; }
#endif /* CONFIG_DEV_BOOT_CONSTRAINTS */

#endif /* _LINUX_BOOT_CONSTRAINT_H */
--
2.13.0.71.gd7076ec9c9cb
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