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Subject[PATCH V4 08/12] 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/dd.c | 12 ++
drivers/boot_constraints/Makefile | 2 +-
drivers/boot_constraints/deferrable_dev.c | 235 ++++++++++++++++++++++++++++++
include/linux/boot_constraint.h | 14 ++
4 files changed, 262 insertions(+), 1 deletion(-)
create mode 100644 drivers/boot_constraints/deferrable_dev.c

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 4eec27fe2b2b..19eff5d08b9a 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -228,6 +228,18 @@ void device_unblock_probing(void)
driver_deferred_probe_trigger();
}

+/**
+ * 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
*
diff --git a/drivers/boot_constraints/Makefile b/drivers/boot_constraints/Makefile
index b7ade1a7afb5..a765094623a3 100644
--- a/drivers/boot_constraints/Makefile
+++ b/drivers/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/boot_constraints/deferrable_dev.c b/drivers/boot_constraints/deferrable_dev.c
new file mode 100644
index 000000000000..04056f317aff
--- /dev/null
+++ b/drivers/boot_constraints/deferrable_dev.c
@@ -0,0 +1,235 @@
+/*
+ * 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/amba/bus.h>
+#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 "core.h"
+
+static DEFINE_IDA(pdev_index);
+
+void driver_enable_deferred_probe(void);
+
+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;
+}
+
+static int dev_boot_constraint_add_deferrable(struct device *dev,
+ struct dev_boot_constraint *constraints, int count)
+{
+ int ret, i;
+
+ for (i = 0; i < count; i++) {
+ ret = boot_constraint_add_dev(dev, &constraints[i]);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+/* This only creates platform devices for now */
+static void add_deferrable_of_single(struct device_node *np,
+ struct dev_boot_constraint *constraints,
+ int count)
+{
+ struct device *dev;
+ int ret;
+
+ if (!of_device_is_available(np))
+ return;
+
+ ret = of_platform_bus_create(np, NULL, NULL, NULL, false);
+ if (ret)
+ return;
+
+ if (of_device_is_compatible(np, "arm,primecell")) {
+ struct amba_device *adev = of_find_amba_device_by_node(np);
+
+ if (!adev) {
+ pr_err("Failed to find amba dev: %s\n", np->full_name);
+ return;
+ }
+ dev = &adev->dev;
+ } else {
+ struct platform_device *pdev = of_find_device_by_node(np);
+
+ if (!pdev) {
+ pr_err("Failed to find pdev: %s\n", np->full_name);
+ return;
+ }
+ dev = &pdev->dev;
+ }
+
+ ret = dev_boot_constraint_add_deferrable(dev, constraints, count);
+ if (ret)
+ dev_err(dev, "Failed to add boot constraint (%d)\n", ret);
+}
+
+/* Not all compatible device nodes may have boot constraints */
+static bool node_has_boot_constraints(struct device_node *np,
+ struct dev_boot_constraint_of *oconst)
+{
+ int i;
+
+ if (!oconst->dev_names)
+ return true;
+
+ for (i = 0; i < oconst->dev_names_count; i++) {
+ if (!strcmp(oconst->dev_names[i], kbasename(np->full_name)))
+ return true;
+ }
+
+ return false;
+}
+
+void dev_boot_constraint_add_deferrable_of(struct dev_boot_constraint_of *oconst,
+ int count)
+{
+ struct device_node *np;
+ int i;
+
+ for (i = 0; i < count; i++) {
+ for_each_compatible_node(np, NULL, oconst[i].compat) {
+ if (!node_has_boot_constraints(np, &oconst[i]))
+ continue;
+
+ add_deferrable_of_single(np, oconst[i].constraints,
+ oconst[i].count);
+ }
+ }
+}
+EXPORT_SYMBOL_GPL(dev_boot_constraint_add_deferrable_of);
diff --git a/include/linux/boot_constraint.h b/include/linux/boot_constraint.h
index 637fe9d65536..c110b36e490f 100644
--- a/include/linux/boot_constraint.h
+++ b/include/linux/boot_constraint.h
@@ -35,6 +35,15 @@ struct dev_boot_constraint {
void *data;
};

+struct dev_boot_constraint_of {
+ const char *compat;
+ struct dev_boot_constraint *constraints;
+ unsigned int count;
+
+ const char **dev_names;
+ unsigned int dev_names_count;
+};
+
struct dev_boot_constraint_info {
struct dev_boot_constraint constraint;

@@ -47,12 +56,17 @@ 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);
+void dev_boot_constraint_add_deferrable_of(struct dev_boot_constraint_of *oconst,
+ 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) {}
+void dev_boot_constraint_add_deferrable_of(struct dev_boot_constraint_of *oconst,
+ int count)
+{ }
#endif /* CONFIG_DEV_BOOT_CONSTRAINTS */

#endif /* _LINUX_BOOT_CONSTRAINT_H */
--
2.15.0.rc1.236.g92ea95045093
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