kernel/linux.git/drivers/clk/clk.c, branch v6.12.80

clk: check for disabled clock-provider in of_clk_get_hw_from_clkspec()

2025-05-02T05:59:15+00:00

[ Upstream commit b20150d499b3ee5c2d632fbc5ac94f98dd33accf ] of_clk_get_hw_from_clkspec() checks all available clock-providers by comparing their of nodes to the one from the clkspec. If no matching clock provider is found, the function returns -EPROBE_DEFER to cause a re-check at a later date. If a matching clock provider is found, an authoritative answer can be retrieved from it whether the clock exists or not. This does not take into account that the clock-provider may never appear, because it's node is disabled. This can happen when a clock is optional, provided by a separate block which never gets enabled. One example of this happening is the rk3588's VOP, which has optional additional display clocks coming from PLLs inside the hdmiphy blocks. These can be used for better rates, but the system will also work without them. The problem around that is described in the followups to[1]. As we already know the of node of the presumed clock provider, add a check via of_device_is_available() whether this is a "valid" device node. This prevents eternal defer loops. Link: https://lore.kernel.org/dri-devel/20250215-vop2-hdmi1-disp-modes-v1-3-81962a7151d6@collabora.com/ [1] Reviewed-by: Sebastian Reichel Tested-by: Cristian Ciocaltea Signed-off-by: Heiko Stuebner Link: https://lore.kernel.org/r/20250222223733.2990179-1-heiko@sntech.de [sboyd@kernel.org: Reword commit text a bit] Signed-off-by: Stephen Boyd Signed-off-by: Sasha Levin

clk: fix an OF node reference leak in of_clk_get_parent_name()

2025-02-08T08:57:03+00:00

[ Upstream commit 28fa3291cad1c201967ef93edc6e7f8ccc9afbc0 ] Current implementation of of_clk_get_parent_name() leaks an OF node reference on error path. Add a of_node_put() call before returning an error. This bug was found by an experimental static analysis tool that I am developing. Fixes: 8da411cc1964 ("clk: let of_clk_get_parent_name() fail for invalid clock-indices") Signed-off-by: Joe Hattori Link: https://lore.kernel.org/r/20241210130913.3615205-1-joe@pf.is.s.u-tokyo.ac.jp Signed-off-by: Stephen Boyd Signed-off-by: Sasha Levin

clk: use clk_core_unlink_consumer() helper

2024-08-06T21:49:25+00:00

There is an helper to remove a consumer from the clk provider list. Hence, let's use it when releasing a consumer. Signed-off-by: Nuno Sá Link: https://lore.kernel.org/r/20240710-dev-clk-misc-v1-2-cd9d960099a2@analog.com Signed-off-by: Stephen Boyd

clk: Use of_property_present()

2024-08-02T23:53:38+00:00

Use of_property_present() to test for property presence rather than of_(find|get)_property(). This is part of a larger effort to remove callers of of_find_property() and similar functions. of_(find|get)_property() leak the DT struct property and data pointers which is a problem for dynamically allocated nodes which may be freed. Signed-off-by: Rob Herring (Arm) Link: https://lore.kernel.org/r/20240731191312.1710417-4-robh@kernel.org Reviewed-by: Linus Walleij Acked-by: Geert Uytterhoeven # clk-mstp.c Reviewed-by: Geert Uytterhoeven Signed-off-by: Stephen Boyd

of: remove internal arguments from of_property_for_each_u32()

2024-07-25T11:53:47+00:00

The of_property_for_each_u32() macro needs five parameters, two of which are primarily meant as internal variables for the macro itself (in the for() clause). Yet these two parameters are used by a few drivers, and this can be considered misuse or at least bad practice. Now that the kernel uses C11 to build, these two parameters can be avoided by declaring them internally, thus changing this pattern: struct property *prop; const __be32 *p; u32 val; of_property_for_each_u32(np, "xyz", prop, p, val) { ... } to this: u32 val; of_property_for_each_u32(np, "xyz", val) { ... } However two variables cannot be declared in the for clause even with C11, so declare one struct that contain the two variables we actually need. As the variables inside this struct are not meant to be used by users of this macro, give the struct instance the noticeable name "_it" so it is visible during code reviews, helping to avoid new code to use it directly. Most usages are trivially converted as they do not use those two parameters, as expected. The non-trivial cases are: - drivers/clk/clk.c, of_clk_get_parent_name(): easily doable anyway - drivers/clk/clk-si5351.c, si5351_dt_parse(): this is more complex as the checks had to be replicated in a different way, making code more verbose and somewhat uglier, but I refrained from a full rework to keep as much of the original code untouched having no hardware to test my changes All the changes have been build tested. The few for which I have the hardware have been runtime-tested too. Reviewed-by: Andre Przywara # drivers/clk/sunxi/clk-simple-gates.c, drivers/clk/sunxi/clk-sun8i-bus-gates.c Acked-by: Bartosz Golaszewski # drivers/gpio/gpio-brcmstb.c Acked-by: Nicolas Ferre # drivers/irqchip/irq-atmel-aic-common.c Acked-by: Jonathan Cameron # drivers/iio/adc/ti_am335x_adc.c Acked-by: Uwe Kleine-König # drivers/pwm/pwm-samsung.c Acked-by: Richard Leitner # drivers/usb/misc/usb251xb.c Acked-by: Mark Brown # sound/soc/codecs/arizona.c Reviewed-by: Richard Fitzgerald # sound/soc/codecs/arizona.c Acked-by: Michael Ellerman # arch/powerpc/sysdev/xive/spapr.c Acked-by: Stephen Boyd # clk Signed-off-by: Luca Ceresoli Acked-by: Lee Jones Link: https://lore.kernel.org/r/20240724-of_property_for_each_u32-v3-1-bea82ce429e2@bootlin.com Signed-off-by: Rob Herring (Arm)

clk: Get runtime PM before walking tree for clk_summary

2024-04-08T02:31:31+00:00

Similar to the previous commit, we should make sure that all devices are runtime resumed before printing the clk_summary through debugfs. Failure to do so would result in a deadlock if the thread is resuming a device to print clk state and that device is also runtime resuming in another thread, e.g the screen is turning on and the display driver is starting up. We remove the calls to clk_pm_runtime_{get,put}() in this path because they're superfluous now that we know the devices are runtime resumed. This also squashes a bug where the return value of clk_pm_runtime_get() wasn't checked, leading to an RPM count underflow on error paths. Fixes: 1bb294a7981c ("clk: Enable/Disable runtime PM for clk_summary") Cc: Taniya Das Cc: Douglas Anderson Signed-off-by: Stephen Boyd Link: https://lore.kernel.org/r/20240325184204.745706-6-sboyd@kernel.org Reviewed-by: Douglas Anderson

clk: Get runtime PM before walking tree during disable_unused

2024-04-08T02:31:30+00:00

Doug reported [1] the following hung task: INFO: task swapper/0:1 blocked for more than 122 seconds. Not tainted 5.15.149-21875-gf795ebc40eb8 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:swapper/0 state:D stack: 0 pid: 1 ppid: 0 flags:0x00000008 Call trace: __switch_to+0xf4/0x1f4 __schedule+0x418/0xb80 schedule+0x5c/0x10c rpm_resume+0xe0/0x52c rpm_resume+0x178/0x52c __pm_runtime_resume+0x58/0x98 clk_pm_runtime_get+0x30/0xb0 clk_disable_unused_subtree+0x58/0x208 clk_disable_unused_subtree+0x38/0x208 clk_disable_unused_subtree+0x38/0x208 clk_disable_unused_subtree+0x38/0x208 clk_disable_unused_subtree+0x38/0x208 clk_disable_unused+0x4c/0xe4 do_one_initcall+0xcc/0x2d8 do_initcall_level+0xa4/0x148 do_initcalls+0x5c/0x9c do_basic_setup+0x24/0x30 kernel_init_freeable+0xec/0x164 kernel_init+0x28/0x120 ret_from_fork+0x10/0x20 INFO: task kworker/u16:0:9 blocked for more than 122 seconds. Not tainted 5.15.149-21875-gf795ebc40eb8 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u16:0 state:D stack: 0 pid: 9 ppid: 2 flags:0x00000008 Workqueue: events_unbound deferred_probe_work_func Call trace: __switch_to+0xf4/0x1f4 __schedule+0x418/0xb80 schedule+0x5c/0x10c schedule_preempt_disabled+0x2c/0x48 __mutex_lock+0x238/0x488 __mutex_lock_slowpath+0x1c/0x28 mutex_lock+0x50/0x74 clk_prepare_lock+0x7c/0x9c clk_core_prepare_lock+0x20/0x44 clk_prepare+0x24/0x30 clk_bulk_prepare+0x40/0xb0 mdss_runtime_resume+0x54/0x1c8 pm_generic_runtime_resume+0x30/0x44 __genpd_runtime_resume+0x68/0x7c genpd_runtime_resume+0x108/0x1f4 __rpm_callback+0x84/0x144 rpm_callback+0x30/0x88 rpm_resume+0x1f4/0x52c rpm_resume+0x178/0x52c __pm_runtime_resume+0x58/0x98 __device_attach+0xe0/0x170 device_initial_probe+0x1c/0x28 bus_probe_device+0x3c/0x9c device_add+0x644/0x814 mipi_dsi_device_register_full+0xe4/0x170 devm_mipi_dsi_device_register_full+0x28/0x70 ti_sn_bridge_probe+0x1dc/0x2c0 auxiliary_bus_probe+0x4c/0x94 really_probe+0xcc/0x2c8 __driver_probe_device+0xa8/0x130 driver_probe_device+0x48/0x110 __device_attach_driver+0xa4/0xcc bus_for_each_drv+0x8c/0xd8 __device_attach+0xf8/0x170 device_initial_probe+0x1c/0x28 bus_probe_device+0x3c/0x9c deferred_probe_work_func+0x9c/0xd8 process_one_work+0x148/0x518 worker_thread+0x138/0x350 kthread+0x138/0x1e0 ret_from_fork+0x10/0x20 The first thread is walking the clk tree and calling clk_pm_runtime_get() to power on devices required to read the clk hardware via struct clk_ops::is_enabled(). This thread holds the clk prepare_lock, and is trying to runtime PM resume a device, when it finds that the device is in the process of resuming so the thread schedule()s away waiting for the device to finish resuming before continuing. The second thread is runtime PM resuming the same device, but the runtime resume callback is calling clk_prepare(), trying to grab the prepare_lock waiting on the first thread. This is a classic ABBA deadlock. To properly fix the deadlock, we must never runtime PM resume or suspend a device with the clk prepare_lock held. Actually doing that is near impossible today because the global prepare_lock would have to be dropped in the middle of the tree, the device runtime PM resumed/suspended, and then the prepare_lock grabbed again to ensure consistency of the clk tree topology. If anything changes with the clk tree in the meantime, we've lost and will need to start the operation all over again. Luckily, most of the time we're simply incrementing or decrementing the runtime PM count on an active device, so we don't have the chance to schedule away with the prepare_lock held. Let's fix this immediate problem that can be triggered more easily by simply booting on Qualcomm sc7180. Introduce a list of clk_core structures that have been registered, or are in the process of being registered, that require runtime PM to operate. Iterate this list and call clk_pm_runtime_get() on each of them without holding the prepare_lock during clk_disable_unused(). This way we can be certain that the runtime PM state of the devices will be active and resumed so we can't schedule away while walking the clk tree with the prepare_lock held. Similarly, call clk_pm_runtime_put() without the prepare_lock held to properly drop the runtime PM reference. We remove the calls to clk_pm_runtime_{get,put}() in this path because they're superfluous now that we know the devices are runtime resumed. Reported-by: Douglas Anderson Closes: https://lore.kernel.org/all/20220922084322.RFC.2.I375b6b9e0a0a5348962f004beb3dafee6a12dfbb@changeid/ [1] Closes: https://issuetracker.google.com/328070191 Cc: Marek Szyprowski Cc: Ulf Hansson Cc: Krzysztof Kozlowski Fixes: 9a34b45397e5 ("clk: Add support for runtime PM") Signed-off-by: Stephen Boyd Link: https://lore.kernel.org/r/20240325184204.745706-5-sboyd@kernel.org Reviewed-by: Douglas Anderson

clk: Initialize struct clk_core kref earlier

2024-04-08T02:29:51+00:00

Initialize this kref once we allocate memory for the struct clk_core so that we can reuse the release function to free any memory associated with the structure. This mostly consolidates code, but also clarifies that the kref lifetime exists once the container structure (struct clk_core) is allocated instead of leaving it in a half-baked state for most of __clk_core_init(). Reviewed-by: Douglas Anderson Signed-off-by: Stephen Boyd Link: https://lore.kernel.org/r/20240325184204.745706-4-sboyd@kernel.org

clk: Don't hold prepare_lock when calling kref_put()

2024-04-08T02:29:51+00:00

We don't need to hold the prepare_lock when dropping a ref on a struct clk_core. The release function is only freeing memory and any code with a pointer reference has already unlinked anything pointing to the clk_core. This reduces the holding area of the prepare_lock a bit. Note that we also don't call free_clk() with the prepare_lock held. There isn't any reason to do that. Reviewed-by: Douglas Anderson Signed-off-by: Stephen Boyd Link: https://lore.kernel.org/r/20240325184204.745706-3-sboyd@kernel.org

clk: Remove prepare_lock hold assertion in __clk_release()

2024-04-08T02:29:51+00:00

Removing this assertion lets us move the kref_put() call outside the prepare_lock section. We don't need to hold the prepare_lock here to free memory and destroy the clk_core structure. We've already unlinked the clk from the clk tree and by the time the release function runs nothing holds a reference to the clk_core anymore so anything with the pointer can't access the memory that's being freed anyway. Way back in commit 496eadf821c2 ("clk: Use lockdep asserts to find missing hold of prepare_lock") we didn't need to have this assertion either. Fixes: 496eadf821c2 ("clk: Use lockdep asserts to find missing hold of prepare_lock") Cc: Krzysztof Kozlowski Reviewed-by: Douglas Anderson Signed-off-by: Stephen Boyd Link: https://lore.kernel.org/r/20240325184204.745706-2-sboyd@kernel.org