4cc47e8add
We shouldn't be calling runtime PM APIs from within the genpd
enable/disable path for a couple reasons.
First, this causes an AA lockdep splat[1] because genpd can call into
genpd code again while holding the genpd lock.
WARNING: possible recursive locking detected
5.19.0-rc2-lockdep+ #7 Not tainted
--------------------------------------------
kworker/2:1/49 is trying to acquire lock:
ffffffeea0370788 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
but task is already holding lock:
ffffffeea03710a8 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&genpd->mlock);
lock(&genpd->mlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by kworker/2:1/49:
#0: 74ffff80811a5748 ((wq_completion)pm){+.+.}-{0:0}, at: process_one_work+0x320/0x5fc
#1: ffffffc008537cf8 ((work_completion)(&genpd->power_off_work)){+.+.}-{0:0}, at: process_one_work+0x354/0x5fc
#2: ffffffeea03710a8 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
stack backtrace:
CPU: 2 PID: 49 Comm: kworker/2:1 Not tainted 5.19.0-rc2-lockdep+ #7
Hardware name: Google Lazor (rev3 - 8) with KB Backlight (DT)
Workqueue: pm genpd_power_off_work_fn
Call trace:
dump_backtrace+0x1a0/0x200
show_stack+0x24/0x30
dump_stack_lvl+0x7c/0xa0
dump_stack+0x18/0x44
__lock_acquire+0xb38/0x3634
lock_acquire+0x180/0x2d4
__mutex_lock_common+0x118/0xe30
mutex_lock_nested+0x70/0x7c
genpd_lock_mtx+0x24/0x30
genpd_runtime_suspend+0x2f0/0x414
__rpm_callback+0xdc/0x1b8
rpm_callback+0x4c/0xcc
rpm_suspend+0x21c/0x5f0
rpm_idle+0x17c/0x1e0
__pm_runtime_idle+0x78/0xcc
gdsc_disable+0x24c/0x26c
_genpd_power_off+0xd4/0x1c4
genpd_power_off+0x2d8/0x41c
genpd_power_off_work_fn+0x60/0x94
process_one_work+0x398/0x5fc
worker_thread+0x42c/0x6c4
kthread+0x194/0x1b4
ret_from_fork+0x10/0x20
Second, this confuses runtime PM on CoachZ for the camera devices by
causing the camera clock controller's runtime PM usage_count to go
negative after resuming from suspend. This is because runtime PM is
being used on the clock controller while runtime PM is disabled for the
device.
The reason for the negative count is because a GDSC is represented as a
genpd and each genpd that is attached to a device is resumed during the
noirq phase of system wide suspend/resume (see the noirq suspend ops
assignment in pm_genpd_init() for more details). The camera GDSCs are
attached to camera devices with the 'power-domains' property in DT.
Every device has runtime PM disabled in the late system suspend phase
via __device_suspend_late(). Runtime PM is not usable until runtime PM
is enabled in device_resume_early(). The noirq phases run after the
'late' and before the 'early' phase of suspend/resume. When the genpds
are resumed in genpd_resume_noirq(), we call down into gdsc_enable()
that calls pm_runtime_resume_and_get() and that returns -EACCES to
indicate failure to resume because runtime PM is disabled for all
devices.
Upon closer inspection, calling runtime PM APIs like this in the GDSC
driver doesn't make sense. It was intended to make sure the GDSC for the
clock controller providing other GDSCs was enabled, specifically the
MMCX GDSC for the display clk controller on SM8250 (sm8250-dispcc), so
that GDSC register accesses succeeded. That will already happen because
we make the 'dev->pm_domain' a parent domain of each GDSC we register in
gdsc_register() via pm_genpd_add_subdomain(). When any of these GDSCs
are accessed, we'll enable the parent domain (in this specific case
MMCX).
We also remove any getting of runtime PM during registration, because
when a genpd is registered it increments the count on the parent if the
genpd itself is already enabled.
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Johan Hovold <johan+linaro@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Taniya Das <quic_tdas@quicinc.com>
Cc: Satya Priya <quic_c_skakit@quicinc.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Reported-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/CAE-0n52xbZeJ66RaKwggeRB57fUAwjvxGxfFMKOKJMKVyFTe+w@mail.gmail.com [1]
Fixes:
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.