| Message ID | 20200610011934.49795-3-saravanak@google.com |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | fw_devlink: Improve cycle detection in DT | expand |
| Context | Check | Description |
|---|---|---|
| robh/checkpatch | success |
On Tue, 09 Jun 2020 18:19:34 -0700, Saravana Kannan wrote: > Consider this example where -> means LHS device is a consumer of RHS > device and indentation represents "child of" of the previous device. > > Device A -> Device C > > Device B -> Device A > Device C > > Without this commit: > 1. Device A is added. > 2. Device A is added to waiting for supplier list (Device C) > 3. Device B is added > 4. Device B is linked as a consumer to Device A > 5. Device A doesn't probe because it's waiting for Device C to be added. > 6. Device B doesn't probe because Device A hasn't probed. > 7. Device C will never be added because it's parent hasn't probed. > > So, Device A, B and C will be in a probe/add deadlock. > > This commit detects this scenario and stops trying to create a device > link between Device A and Device C since doing so would create the > following cycle: > Device A -> Devic C -(parent)-> Device B -> Device A. > > With this commit: > 1. Device A is added. > 3. Device B is added > 4. Device B is linked as a consumer to Device A > 5. Device A probes. > 6. Device B probes because Device A has probed. > 7. Device C is added and probed. > > Signed-off-by: Saravana Kannan <saravanak@google.com> > --- > drivers/of/property.c | 62 ++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 56 insertions(+), 6 deletions(-) > Both patches applied. Rob
On Wed, Jun 17, 2020 at 3:12 PM Rob Herring <robh@kernel.org> wrote: > > On Tue, 09 Jun 2020 18:19:34 -0700, Saravana Kannan wrote: > > Consider this example where -> means LHS device is a consumer of RHS > > device and indentation represents "child of" of the previous device. > > > > Device A -> Device C > > > > Device B -> Device A > > Device C > > > > Without this commit: > > 1. Device A is added. > > 2. Device A is added to waiting for supplier list (Device C) > > 3. Device B is added > > 4. Device B is linked as a consumer to Device A > > 5. Device A doesn't probe because it's waiting for Device C to be added. > > 6. Device B doesn't probe because Device A hasn't probed. > > 7. Device C will never be added because it's parent hasn't probed. > > > > So, Device A, B and C will be in a probe/add deadlock. > > > > This commit detects this scenario and stops trying to create a device > > link between Device A and Device C since doing so would create the > > following cycle: > > Device A -> Devic C -(parent)-> Device B -> Device A. > > > > With this commit: > > 1. Device A is added. > > 3. Device B is added > > 4. Device B is linked as a consumer to Device A > > 5. Device A probes. > > 6. Device B probes because Device A has probed. > > 7. Device C is added and probed. > > > > Signed-off-by: Saravana Kannan <saravanak@google.com> > > --- > > drivers/of/property.c | 62 ++++++++++++++++++++++++++++++++++++++----- > > 1 file changed, 56 insertions(+), 6 deletions(-) > > > > Both patches applied. Thanks! -Saravana
diff --git a/drivers/of/property.c b/drivers/of/property.c index 1f2086f4e7ce..ef09e4372ce8 100644 --- a/drivers/of/property.c +++ b/drivers/of/property.c @@ -1014,6 +1014,30 @@ static bool of_is_ancestor_of(struct device_node *test_ancestor, return false; } +/** + * of_get_next_parent_dev - Add device link to supplier from supplier phandle + * @np: device tree node + * + * Given a device tree node (@np), this function finds its closest ancestor + * device tree node that has a corresponding struct device. + * + * The caller of this function is expected to call put_device() on the returned + * device when they are done. + */ +static struct device *of_get_next_parent_dev(struct device_node *np) +{ + struct device *dev = NULL; + + of_node_get(np); + do { + np = of_get_next_parent(np); + if (np) + dev = get_dev_from_fwnode(&np->fwnode); + } while (np && !dev); + of_node_put(np); + return dev; +} + /** * of_link_to_phandle - Add device link to supplier from supplier phandle * @dev: consumer device @@ -1035,10 +1059,9 @@ static bool of_is_ancestor_of(struct device_node *test_ancestor, static int of_link_to_phandle(struct device *dev, struct device_node *sup_np, u32 dl_flags) { - struct device *sup_dev; + struct device *sup_dev, *sup_par_dev; int ret = 0; struct device_node *tmp_np = sup_np; - int is_populated; of_node_get(sup_np); /* @@ -1075,16 +1098,43 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np, return -EINVAL; } sup_dev = get_dev_from_fwnode(&sup_np->fwnode); - is_populated = of_node_check_flag(sup_np, OF_POPULATED); - of_node_put(sup_np); - if (!sup_dev && is_populated) { + if (!sup_dev && of_node_check_flag(sup_np, OF_POPULATED)) { /* Early device without struct device. */ dev_dbg(dev, "Not linking to %pOFP - No struct device\n", sup_np); + of_node_put(sup_np); return -ENODEV; } else if (!sup_dev) { - return -EAGAIN; + /* + * DL_FLAG_SYNC_STATE_ONLY doesn't block probing and supports + * cycles. So cycle detection isn't necessary and shouldn't be + * done. + */ + if (dl_flags & DL_FLAG_SYNC_STATE_ONLY) { + of_node_put(sup_np); + return -EAGAIN; + } + + sup_par_dev = of_get_next_parent_dev(sup_np); + + if (sup_par_dev && device_is_dependent(dev, sup_par_dev)) { + /* Cyclic dependency detected, don't try to link */ + dev_dbg(dev, "Not linking to %pOFP - cycle detected\n", + sup_np); + ret = -EINVAL; + } else { + /* + * Can't check for cycles or no cycles. So let's try + * again later. + */ + ret = -EAGAIN; + } + + of_node_put(sup_np); + put_device(sup_par_dev); + return ret; } + of_node_put(sup_np); if (!device_link_add(dev, sup_dev, dl_flags)) ret = -EINVAL; put_device(sup_dev);
Consider this example where -> means LHS device is a consumer of RHS device and indentation represents "child of" of the previous device. Device A -> Device C Device B -> Device A Device C Without this commit: 1. Device A is added. 2. Device A is added to waiting for supplier list (Device C) 3. Device B is added 4. Device B is linked as a consumer to Device A 5. Device A doesn't probe because it's waiting for Device C to be added. 6. Device B doesn't probe because Device A hasn't probed. 7. Device C will never be added because it's parent hasn't probed. So, Device A, B and C will be in a probe/add deadlock. This commit detects this scenario and stops trying to create a device link between Device A and Device C since doing so would create the following cycle: Device A -> Devic C -(parent)-> Device B -> Device A. With this commit: 1. Device A is added. 3. Device B is added 4. Device B is linked as a consumer to Device A 5. Device A probes. 6. Device B probes because Device A has probed. 7. Device C is added and probed. Signed-off-by: Saravana Kannan <saravanak@google.com> --- drivers/of/property.c | 62 ++++++++++++++++++++++++++++++++++++++----- 1 file changed, 56 insertions(+), 6 deletions(-)