From 7fddac12c38237252431d5b8af7b6d5771b6d125 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Fri, 2 Feb 2024 01:56:33 -0800 Subject: driver core: Fix device_link_flag_is_sync_state_only() device_link_flag_is_sync_state_only() correctly returns true on the flags of an existing device link that only implements sync_state() functionality. However, it incorrectly and confusingly returns false if it's called with DL_FLAG_SYNC_STATE_ONLY. This bug doesn't manifest in any of the existing calls to this function, but fix this confusing behavior to avoid future bugs. Fixes: 67cad5c67019 ("driver core: fw_devlink: Add DL_FLAG_CYCLE support to device links") Signed-off-by: Saravana Kannan Tested-by: Xu Yang Link: https://lore.kernel.org/r/20240202095636.868578-2-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'drivers/base/core.c') diff --git a/drivers/base/core.c b/drivers/base/core.c index 14d46af40f9a..52215c4c7209 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -284,10 +284,12 @@ static bool device_is_ancestor(struct device *dev, struct device *target) return false; } +#define DL_MARKER_FLAGS (DL_FLAG_INFERRED | \ + DL_FLAG_CYCLE | \ + DL_FLAG_MANAGED) static inline bool device_link_flag_is_sync_state_only(u32 flags) { - return (flags & ~(DL_FLAG_INFERRED | DL_FLAG_CYCLE)) == - (DL_FLAG_SYNC_STATE_ONLY | DL_FLAG_MANAGED); + return (flags & ~DL_MARKER_FLAGS) == DL_FLAG_SYNC_STATE_ONLY; } /** -- cgit v1.2.3-70-g09d2 From 6442d79d880cf7a2fff18779265d657fef0cce4c Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Fri, 2 Feb 2024 01:56:34 -0800 Subject: driver core: fw_devlink: Improve detection of overlapping cycles fw_devlink can detect most overlapping/intersecting cycles. However it was missing a few corner cases because of an incorrect optimization logic that tries to avoid repeating cycle detection for devices that are already marked as part of a cycle. Here's an example provided by Xu Yang (edited for clarity): usb +-----+ tcpc | | +-----+ | +--| | |----------->|EP| |--+ | | +--| |EP|<-----------| | |--+ | | B | | | +-----+ | A | | +-----+ | ^ +-----+ | | | | | +-----| C |<--+ | | +-----+ usb-phy Node A (tcpc) will be populated as device 1-0050. Node B (usb) will be populated as device 38100000.usb. Node C (usb-phy) will be populated as device 381f0040.usb-phy. The description below uses the notation: consumer --> supplier child ==> parent 1. Node C is populated as device C. No cycles detected because cycle detection is only run when a fwnode link is converted to a device link. 2. Node B is populated as device B. As we convert B --> C into a device link we run cycle detection and find and mark the device link/fwnode link cycle: C--> A --> B.EP ==> B --> C 3. Node A is populated as device A. As we convert C --> A into a device link, we see it's already part of a cycle (from step 2) and don't run cycle detection. Thus we miss detecting the cycle: A --> B.EP ==> B --> A.EP ==> A Looking at it another way, A depends on B in one way: A --> B.EP ==> B But B depends on A in two ways and we only detect the first: B --> C --> A B --> A.EP ==> A To detect both of these, we remove the incorrect optimization attempt in step 3 and run cycle detection even if the fwnode link from which the device link is being created has already been marked as part of a cycle. Reported-by: Xu Yang Closes: https://lore.kernel.org/lkml/DU2PR04MB8822693748725F85DC0CB86C8C792@DU2PR04MB8822.eurprd04.prod.outlook.com/ Fixes: 3fb16866b51d ("driver core: fw_devlink: Make cycle detection more robust") Signed-off-by: Saravana Kannan Tested-by: Xu Yang Link: https://lore.kernel.org/r/20240202095636.868578-3-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'drivers/base/core.c') diff --git a/drivers/base/core.c b/drivers/base/core.c index 52215c4c7209..e3d666461835 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -2060,9 +2060,14 @@ static int fw_devlink_create_devlink(struct device *con, /* * SYNC_STATE_ONLY device links don't block probing and supports cycles. - * So cycle detection isn't necessary and shouldn't be done. + * So, one might expect that cycle detection isn't necessary for them. + * However, if the device link was marked as SYNC_STATE_ONLY because + * it's part of a cycle, then we still need to do cycle detection. This + * is because the consumer and supplier might be part of multiple cycles + * and we need to detect all those cycles. */ - if (!(flags & DL_FLAG_SYNC_STATE_ONLY)) { + if (!device_link_flag_is_sync_state_only(flags) || + flags & DL_FLAG_CYCLE) { device_links_write_lock(); if (__fw_devlink_relax_cycles(con, sup_handle)) { __fwnode_link_cycle(link); -- cgit v1.2.3-70-g09d2 From 6e7ad1aebb4fc9fed0217dd50ef6e58a53f17d81 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Fri, 2 Feb 2024 01:56:35 -0800 Subject: driver core: fw_devlink: Improve logs for cycle detection The links in a cycle are not all logged in a consistent manner or not logged at all. Make them consistent by adding a "cycle:" string and log all the link in the cycles (even the child ==> parent dependency) so that it's easier to debug cycle detection code. Also, mark the start and end of a cycle so it's easy to tell when multiple cycles are logged back to back. Signed-off-by: Saravana Kannan Tested-by: Xu Yang Link: https://lore.kernel.org/r/20240202095636.868578-4-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'drivers/base/core.c') diff --git a/drivers/base/core.c b/drivers/base/core.c index e3d666461835..9828da9b933c 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -125,7 +125,7 @@ static void __fwnode_link_del(struct fwnode_link *link) */ static void __fwnode_link_cycle(struct fwnode_link *link) { - pr_debug("%pfwf: Relaxing link with %pfwf\n", + pr_debug("%pfwf: cycle: depends on %pfwf\n", link->consumer, link->supplier); link->flags |= FWLINK_FLAG_CYCLE; } @@ -1945,6 +1945,7 @@ static bool __fw_devlink_relax_cycles(struct device *con, /* Termination condition. */ if (sup_dev == con) { + pr_debug("----- cycle: start -----\n"); ret = true; goto out; } @@ -1976,8 +1977,11 @@ static bool __fw_devlink_relax_cycles(struct device *con, else par_dev = fwnode_get_next_parent_dev(sup_handle); - if (par_dev && __fw_devlink_relax_cycles(con, par_dev->fwnode)) + if (par_dev && __fw_devlink_relax_cycles(con, par_dev->fwnode)) { + pr_debug("%pfwf: cycle: child of %pfwf\n", sup_handle, + par_dev->fwnode); ret = true; + } if (!sup_dev) goto out; @@ -1993,6 +1997,8 @@ static bool __fw_devlink_relax_cycles(struct device *con, if (__fw_devlink_relax_cycles(con, dev_link->supplier->fwnode)) { + pr_debug("%pfwf: cycle: depends on %pfwf\n", sup_handle, + dev_link->supplier->fwnode); fw_devlink_relax_link(dev_link); dev_link->flags |= DL_FLAG_CYCLE; ret = true; @@ -2072,6 +2078,7 @@ static int fw_devlink_create_devlink(struct device *con, if (__fw_devlink_relax_cycles(con, sup_handle)) { __fwnode_link_cycle(link); flags = fw_devlink_get_flags(link->flags); + pr_debug("----- cycle: end -----\n"); dev_info(con, "Fixed dependency cycle(s) with %pfwf\n", sup_handle); } -- cgit v1.2.3-70-g09d2