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driver core: fw_devlink: Allow marking a fwnode link as being part of…
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… a cycle

To improve detection and handling of dependency cycles, we need to be
able to mark fwnode links as being part of cycles. fwnode links marked
as being part of a cycle should not block their consumers from probing.

Fixes: 2de9d8e ("driver core: fw_devlink: Improve handling of cyclic dependencies")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Colin Foster <colin.foster@in-advantage.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Luca Weiss <luca.weiss@fairphone.com> # qcom/sm7225-fairphone-fp4
Link: https://lore.kernel.org/r/20230207014207.1678715-7-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Saravana Kannan authored and Greg Kroah-Hartman committed Feb 8, 2023
1 parent 67cad5c commit 6a6dfdf
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Showing 2 changed files with 50 additions and 11 deletions.
50 changes: 40 additions & 10 deletions drivers/base/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -76,13 +76,15 @@ static bool fw_devlink_best_effort;
* are ignored and there is no reference counting.
*/
static int __fwnode_link_add(struct fwnode_handle *con,
struct fwnode_handle *sup)
struct fwnode_handle *sup, u8 flags)
{
struct fwnode_link *link;

list_for_each_entry(link, &sup->consumers, s_hook)
if (link->consumer == con)
if (link->consumer == con) {
link->flags |= flags;
return 0;
}

link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link)
Expand All @@ -92,6 +94,7 @@ static int __fwnode_link_add(struct fwnode_handle *con,
INIT_LIST_HEAD(&link->s_hook);
link->consumer = con;
INIT_LIST_HEAD(&link->c_hook);
link->flags = flags;

list_add(&link->s_hook, &sup->consumers);
list_add(&link->c_hook, &con->suppliers);
Expand All @@ -106,7 +109,7 @@ int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup)
int ret;

mutex_lock(&fwnode_link_lock);
ret = __fwnode_link_add(con, sup);
ret = __fwnode_link_add(con, sup, 0);
mutex_unlock(&fwnode_link_lock);
return ret;
}
Expand All @@ -126,6 +129,19 @@ static void __fwnode_link_del(struct fwnode_link *link)
kfree(link);
}

/**
* __fwnode_link_cycle - Mark a fwnode link as being part of a cycle.
* @link: the fwnode_link to be marked
*
* The fwnode_link_lock needs to be held when this function is called.
*/
static void __fwnode_link_cycle(struct fwnode_link *link)
{
pr_debug("%pfwf: Relaxing link with %pfwf\n",
link->consumer, link->supplier);
link->flags |= FWLINK_FLAG_CYCLE;
}

/**
* fwnode_links_purge_suppliers - Delete all supplier links of fwnode_handle.
* @fwnode: fwnode whose supplier links need to be deleted
Expand Down Expand Up @@ -199,7 +215,7 @@ static void __fwnode_links_move_consumers(struct fwnode_handle *from,
struct fwnode_link *link, *tmp;

list_for_each_entry_safe(link, tmp, &from->consumers, s_hook) {
__fwnode_link_add(link->consumer, to);
__fwnode_link_add(link->consumer, to, link->flags);
__fwnode_link_del(link);
}
}
Expand Down Expand Up @@ -1041,6 +1057,21 @@ static bool dev_is_best_effort(struct device *dev)
(dev->fwnode && (dev->fwnode->flags & FWNODE_FLAG_BEST_EFFORT));
}

static struct fwnode_handle *fwnode_links_check_suppliers(
struct fwnode_handle *fwnode)
{
struct fwnode_link *link;

if (!fwnode || fw_devlink_is_permissive())
return NULL;

list_for_each_entry(link, &fwnode->suppliers, c_hook)
if (!(link->flags & FWLINK_FLAG_CYCLE))
return link->supplier;

return NULL;
}

/**
* device_links_check_suppliers - Check presence of supplier drivers.
* @dev: Consumer device.
Expand Down Expand Up @@ -1068,11 +1099,8 @@ int device_links_check_suppliers(struct device *dev)
* probe.
*/
mutex_lock(&fwnode_link_lock);
if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
!fw_devlink_is_permissive()) {
sup_fw = list_first_entry(&dev->fwnode->suppliers,
struct fwnode_link,
c_hook)->supplier;
sup_fw = fwnode_links_check_suppliers(dev->fwnode);
if (sup_fw) {
if (!dev_is_best_effort(dev)) {
fwnode_ret = -EPROBE_DEFER;
dev_err_probe(dev, -EPROBE_DEFER,
Expand Down Expand Up @@ -1261,7 +1289,9 @@ static ssize_t waiting_for_supplier_show(struct device *dev,
bool val;

device_lock(dev);
val = !list_empty(&dev->fwnode->suppliers);
mutex_lock(&fwnode_link_lock);
val = !!fwnode_links_check_suppliers(dev->fwnode);
mutex_unlock(&fwnode_link_lock);
device_unlock(dev);
return sysfs_emit(buf, "%u\n", val);
}
Expand Down
11 changes: 10 additions & 1 deletion include/linux/fwnode.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ struct fwnode_operations;
struct device;

/*
* fwnode link flags
* fwnode flags
*
* LINKS_ADDED: The fwnode has already be parsed to add fwnode links.
* NOT_DEVICE: The fwnode will never be populated as a struct device.
Expand All @@ -36,6 +36,7 @@ struct device;
#define FWNODE_FLAG_INITIALIZED BIT(2)
#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD BIT(3)
#define FWNODE_FLAG_BEST_EFFORT BIT(4)
#define FWNODE_FLAG_VISITED BIT(5)

struct fwnode_handle {
struct fwnode_handle *secondary;
Expand All @@ -46,11 +47,19 @@ struct fwnode_handle {
u8 flags;
};

/*
* fwnode link flags
*
* CYCLE: The fwnode link is part of a cycle. Don't defer probe.
*/
#define FWLINK_FLAG_CYCLE BIT(0)

struct fwnode_link {
struct fwnode_handle *supplier;
struct list_head s_hook;
struct fwnode_handle *consumer;
struct list_head c_hook;
u8 flags;
};

/**
Expand Down

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