From: Saravana Kannan <saravanak@xxxxxxxxxx> [ Upstream commit 5501765a02a6c324f78581e6bb8209d054fe13ae ] If a parent device is also a supplier to a child device, fw_devlink=on by design delays the probe() of the child device until the probe() of the parent finishes successfully. However, some drivers of such parent devices (where parent is also a supplier) expect the child device to finish probing successfully as soon as they are added using device_add() and before the probe() of the parent device has completed successfully. One example of such a case is discussed in the link mentioned below. Add a flag to make fw_devlink=on not enforce these supplier-consumer relationships, so these drivers can continue working. Link: https://lore.kernel.org/netdev/CAGETcx_uj0V4DChME-gy5HGKTYnxLBX=TH2rag29f_p=UcG+Tg@xxxxxxxxxxxxxx/ Fixes: ea718c699055 ("Revert "Revert "driver core: Set fw_devlink=on by default""") Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210915170940.617415-3-saravanak@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/base/core.c | 19 +++++++++++++++++++ include/linux/fwnode.h | 11 ++++++++--- 2 files changed, 27 insertions(+), 3 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 8c77e14987d4..3d2fc70b9951 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1721,6 +1721,25 @@ static int fw_devlink_create_devlink(struct device *con, struct device *sup_dev; int ret = 0; + /* + * In some cases, a device P might also be a supplier to its child node + * C. However, this would defer the probe of C until the probe of P + * completes successfully. This is perfectly fine in the device driver + * model. device_add() doesn't guarantee probe completion of the device + * by the time it returns. + * + * However, there are a few drivers that assume C will finish probing + * as soon as it's added and before P finishes probing. So, we provide + * a flag to let fw_devlink know not to delay the probe of C until the + * probe of P completes successfully. + * + * When such a flag is set, we can't create device links where P is the + * supplier of C as that would delay the probe of C. + */ + if (sup_handle->flags & FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD && + fwnode_is_ancestor_of(sup_handle, con->fwnode)) + return -EINVAL; + sup_dev = get_dev_from_fwnode(sup_handle); if (sup_dev) { /* diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h index 59828516ebaf..9f4ad719bfe3 100644 --- a/include/linux/fwnode.h +++ b/include/linux/fwnode.h @@ -22,10 +22,15 @@ struct device; * LINKS_ADDED: The fwnode has already be parsed to add fwnode links. * NOT_DEVICE: The fwnode will never be populated as a struct device. * INITIALIZED: The hardware corresponding to fwnode has been initialized. + * NEEDS_CHILD_BOUND_ON_ADD: For this fwnode/device to probe successfully, its + * driver needs its child devices to be bound with + * their respective drivers as soon as they are + * added. */ -#define FWNODE_FLAG_LINKS_ADDED BIT(0) -#define FWNODE_FLAG_NOT_DEVICE BIT(1) -#define FWNODE_FLAG_INITIALIZED BIT(2) +#define FWNODE_FLAG_LINKS_ADDED BIT(0) +#define FWNODE_FLAG_NOT_DEVICE BIT(1) +#define FWNODE_FLAG_INITIALIZED BIT(2) +#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD BIT(3) struct fwnode_handle { struct fwnode_handle *secondary; -- 2.33.0
