of: property: fw_devlink: Add support for remote-endpoint

remote-endpoint property seems to always come in pairs where two devices
point to each other. So, we can't really tell from DT if there is a
functional probe order dependency between these two devices.

However, there can be other dependencies between two devices that point
to each other with remote-endpoint. This non-remote-endpoint dependency
combined with one of the remote-endpoint dependency can lead to a cyclic
dependency[1].

To avoid this cyclic dependency from incorrectly blocking probes,
fw_devlink needs to be made aware of remote-endpoint dependencies even
though remote-endpoint dependencies by themselves won't affect probe
ordering (because fw_devlink will see the cyclic dependency between
remote-endpoint devices and ignore the dependencies that cause the
cycle).

Also, if a device ever needs to know if a non-probe-blocking
remote-endpoint has finished probing, it can now use the sync_state() to
figure it out.

[1] - https://lore.kernel.org/lkml/CAGETcx9Snf23wrXqjDhJiTok9M3GcoVYDSyNYSMj9QnSRrA=cA@mail.gmail.com/#t

Fixes: ea718c699055 ("Revert "Revert "driver core: Set fw_devlink=on by default""")
Reported-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210330185056.1022008-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 5036a362f52e711ff0a3381b280a2d37e4262022..2bb3158c9e43d1188ad0e0562f1b9b52498946ae 100644 (file)
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1038,6 +1038,25 @@ static bool of_is_ancestor_of(struct device_node *test_ancestor,
        return false;
 }
 
+static struct device_node *of_get_compat_node(struct device_node *np)
+{
+       of_node_get(np);
+
+       while (np) {
+               if (!of_device_is_available(np)) {
+                       of_node_put(np);
+                       np = NULL;
+               }
+
+               if (of_find_property(np, "compatible", NULL))
+                       break;
+
+               np = of_get_next_parent(np);
+       }
+
+       return np;
+}
+
 /**
  * of_link_to_phandle - Add fwnode link to supplier from supplier phandle
  * @con_np: consumer device tree node
@@ -1061,25 +1080,11 @@ static int of_link_to_phandle(struct device_node *con_np,
        struct device *sup_dev;
        struct device_node *tmp_np = sup_np;
 
-       of_node_get(sup_np);
        /*
         * Find the device node that contains the supplier phandle.  It may be
         * @sup_np or it may be an ancestor of @sup_np.
         */
-       while (sup_np) {
-
-               /* Don't allow linking to a disabled supplier */
-               if (!of_device_is_available(sup_np)) {
-                       of_node_put(sup_np);
-                       sup_np = NULL;
-               }
-
-               if (of_find_property(sup_np, "compatible", NULL))
-                       break;
-
-               sup_np = of_get_next_parent(sup_np);
-       }
-
+       sup_np = of_get_compat_node(sup_np);
        if (!sup_np) {
                pr_debug("Not linking %pOFP to %pOFP - No device\n",
                         con_np, tmp_np);
@@ -1225,6 +1230,8 @@ static struct device_node *parse_##fname(struct device_node *np,       \
  * @parse_prop.prop_name: Name of property holding a phandle value
  * @parse_prop.index: For properties holding a list of phandles, this is the
  *                   index into the list
+ * @optional: The property can be an optional dependency.
+ * @node_not_dev: The consumer node containing the property is never a device.
  *
  * Returns:
  * parse_prop() return values are
@@ -1236,6 +1243,7 @@ struct supplier_bindings {
        struct device_node *(*parse_prop)(struct device_node *np,
                                          const char *prop_name, int index);
        bool optional;
+       bool node_not_dev;
 };
 
 DEFINE_SIMPLE_PROP(clocks, "clocks", "#clock-cells")
@@ -1260,6 +1268,7 @@ DEFINE_SIMPLE_PROP(pinctrl5, "pinctrl-5", NULL)
 DEFINE_SIMPLE_PROP(pinctrl6, "pinctrl-6", NULL)
 DEFINE_SIMPLE_PROP(pinctrl7, "pinctrl-7", NULL)
 DEFINE_SIMPLE_PROP(pinctrl8, "pinctrl-8", NULL)
+DEFINE_SIMPLE_PROP(remote_endpoint, "remote-endpoint", NULL)
 DEFINE_SUFFIX_PROP(regulators, "-supply", NULL)
 DEFINE_SUFFIX_PROP(gpio, "-gpio", "#gpio-cells")
 DEFINE_SUFFIX_PROP(gpios, "-gpios", "#gpio-cells")
@@ -1334,6 +1343,7 @@ static const struct supplier_bindings of_supplier_bindings[] = {
        { .parse_prop = parse_pinctrl6, },
        { .parse_prop = parse_pinctrl7, },
        { .parse_prop = parse_pinctrl8, },
+       { .parse_prop = parse_remote_endpoint, .node_not_dev = true, },
        { .parse_prop = parse_gpio_compat, },
        { .parse_prop = parse_interrupts, },
        { .parse_prop = parse_regulators, },
@@ -1378,10 +1388,16 @@ static int of_link_property(struct device_node *con_np, const char *prop_name)
                }
 
                while ((phandle = s->parse_prop(con_np, prop_name, i))) {
+                       struct device_node *con_dev_np;
+
+                       con_dev_np = s->node_not_dev
+                                       ? of_get_compat_node(con_np)
+                                       : of_node_get(con_np);
                        matched = true;
                        i++;
-                       of_link_to_phandle(con_np, phandle);
+                       of_link_to_phandle(con_dev_np, phandle);
                        of_node_put(phandle);
+                       of_node_put(con_dev_np);
                }
                s++;
        }