There are 2 problems with the old iosf PMIC I2C bus arbritration code which
need to be addressed:
1. The lockdep code complains about a possible deadlock in the
iosf_mbi_[un]block_punit_i2c_access code:
[ 6.712662] ======================================================
[ 6.712673] WARNING: possible circular locking dependency detected
[ 6.712685] 5.3.0-rc2+ #79 Not tainted
[ 6.712692] ------------------------------------------------------
[ 6.712702] kworker/0:1/7 is trying to acquire lock:
[ 6.712712] 00000000df1c5681 (iosf_mbi_block_punit_i2c_access_count_mutex){+.+.}, at: iosf_mbi_unblock_punit_i2c_access+0x13/0x90
[ 6.712739]
but task is already holding lock:
[ 6.712749] 0000000067cb23e7 (iosf_mbi_punit_mutex){+.+.}, at: iosf_mbi_block_punit_i2c_access+0x97/0x186
[ 6.712768]
which lock already depends on the new lock.
[ 6.712780]
the existing dependency chain (in reverse order) is:
[ 6.712792]
-> #1 (iosf_mbi_punit_mutex){+.+.}:
[ 6.712808] __mutex_lock+0xa8/0x9a0
[ 6.712818] iosf_mbi_block_punit_i2c_access+0x97/0x186
[ 6.712831] i2c_dw_acquire_lock+0x20/0x30
[ 6.712841] i2c_dw_set_reg_access+0x15/0xb0
[ 6.712851] i2c_dw_probe+0x57/0x473
[ 6.712861] dw_i2c_plat_probe+0x33e/0x640
[ 6.712874] platform_drv_probe+0x38/0x80
[ 6.712884] really_probe+0xf3/0x380
[ 6.712894] driver_probe_device+0x59/0xd0
[ 6.712905] bus_for_each_drv+0x84/0xd0
[ 6.712915] __device_attach+0xe4/0x170
[ 6.712925] bus_probe_device+0x9f/0xb0
[ 6.712935] deferred_probe_work_func+0x79/0xd0
[ 6.712946] process_one_work+0x234/0x560
[ 6.712957] worker_thread+0x50/0x3b0
[ 6.712967] kthread+0x10a/0x140
[ 6.712977] ret_from_fork+0x3a/0x50
[ 6.712986]
-> #0 (iosf_mbi_block_punit_i2c_access_count_mutex){+.+.}:
[ 6.713004] __lock_acquire+0xe07/0x1930
[ 6.713015] lock_acquire+0x9d/0x1a0
[ 6.713025] __mutex_lock+0xa8/0x9a0
[ 6.713035] iosf_mbi_unblock_punit_i2c_access+0x13/0x90
[ 6.713047] i2c_dw_set_reg_access+0x4d/0xb0
[ 6.713058] i2c_dw_probe+0x57/0x473
[ 6.713068] dw_i2c_plat_probe+0x33e/0x640
[ 6.713079] platform_drv_probe+0x38/0x80
[ 6.713089] really_probe+0xf3/0x380
[ 6.713099] driver_probe_device+0x59/0xd0
[ 6.713109] bus_for_each_drv+0x84/0xd0
[ 6.713119] __device_attach+0xe4/0x170
[ 6.713129] bus_probe_device+0x9f/0xb0
[ 6.713140] deferred_probe_work_func+0x79/0xd0
[ 6.713150] process_one_work+0x234/0x560
[ 6.713160] worker_thread+0x50/0x3b0
[ 6.713170] kthread+0x10a/0x140
[ 6.713180] ret_from_fork+0x3a/0x50
[ 6.713189]
other info that might help us debug this:
[ 6.713202] Possible unsafe locking scenario:
[ 6.713212] CPU0 CPU1
[ 6.713221] ---- ----
[ 6.713229] lock(iosf_mbi_punit_mutex);
[ 6.713239] lock(iosf_mbi_block_punit_i2c_access_count_mutex);
[ 6.713253] lock(iosf_mbi_punit_mutex);
[ 6.713265] lock(iosf_mbi_block_punit_i2c_access_count_mutex);
[ 6.713276]
*** DEADLOCK ***
In practice can never happen because only the first caller which
increments iosf_mbi_block_punit_i2c_access_count will also take
iosf_mbi_punit_mutex, that is the whole purpose of the counter, which
itself is protected by iosf_mbi_block_punit_i2c_access_count_mutex.
But there is no way to tell the lockdep code about this and we really
want to be able to run a kernel with lockdep enabled without these
warnings being triggered.
2. The lockdep warning also points out another real problem, if 2 threads
both are in a block of code protected by iosf_mbi_block_punit_i2c_access
and the first thread to acquire the block exits before the second thread
then the second thread will call mutex_unlock on iosf_mbi_punit_mutex,
but it is not the thread which took the mutex and unlocking by another
thread is not allowed.
Fix this by getting rid of the notion of holding a mutex for the entire
duration of the PMIC accesses, be it either from the PUnit side, or from an
in kernel I2C driver. In general holding a mutex after exiting a function
is a bad idea and the above problems show this case is no different.
Instead 2 counters are now used, one for PMIC accesses from the PUnit
and one for accesses from in kernel I2C code. When access is requested
now the code will wait (using a waitqueue) for the counter of the other
type of access to reach 0 and on release, if the counter reaches 0 the
wakequeue is woken.
Note that the counter approach is necessary to allow nested calls.
The main reason for this is so that a series of i2c transfers can be done
with the punit blocked from accessing the bus the whole time. This is
necessary to be able to safely read/modify/write a PMIC register without
racing with the PUNIT doing the same thing.
Allowing nested iosf_mbi_block_punit_i2c_access() calls also is desirable
from a performance pov since the whole dance necessary to block the PUnit
from accessing the PMIC I2C bus is somewhat expensive.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lkml.kernel.org/r/20190812102113.95794-1-hdegoede@redhat.com
Here is the "big" driver core and debugfs changes for 5.3-rc1
It's a lot of different patches, all across the tree due to some api
changes and lots of debugfs cleanups. Because of this, there is going
to be some merge issues with your tree at the moment, I'll follow up
with the expected resolutions to make it easier for you.
Other than the debugfs cleanups, in this set of changes we have:
- bus iteration function cleanups (will cause build warnings
with s390 and coresight drivers in your tree)
- scripts/get_abi.pl tool to display and parse Documentation/ABI
entries in a simple way
- cleanups to Documenatation/ABI/ entries to make them parse
easier due to typos and other minor things
- default_attrs use for some ktype users
- driver model documentation file conversions to .rst
- compressed firmware file loading
- deferred probe fixes
All of these have been in linux-next for a while, with a bunch of merge
issues that Stephen has been patient with me for. Other than the merge
issues, functionality is working properly in linux-next :)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core and debugfs updates from Greg KH:
"Here is the "big" driver core and debugfs changes for 5.3-rc1
It's a lot of different patches, all across the tree due to some api
changes and lots of debugfs cleanups.
Other than the debugfs cleanups, in this set of changes we have:
- bus iteration function cleanups
- scripts/get_abi.pl tool to display and parse Documentation/ABI
entries in a simple way
- cleanups to Documenatation/ABI/ entries to make them parse easier
due to typos and other minor things
- default_attrs use for some ktype users
- driver model documentation file conversions to .rst
- compressed firmware file loading
- deferred probe fixes
All of these have been in linux-next for a while, with a bunch of
merge issues that Stephen has been patient with me for"
* tag 'driver-core-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (102 commits)
debugfs: make error message a bit more verbose
orangefs: fix build warning from debugfs cleanup patch
ubifs: fix build warning after debugfs cleanup patch
driver: core: Allow subsystems to continue deferring probe
drivers: base: cacheinfo: Ensure cpu hotplug work is done before Intel RDT
arch_topology: Remove error messages on out-of-memory conditions
lib: notifier-error-inject: no need to check return value of debugfs_create functions
swiotlb: no need to check return value of debugfs_create functions
ceph: no need to check return value of debugfs_create functions
sunrpc: no need to check return value of debugfs_create functions
ubifs: no need to check return value of debugfs_create functions
orangefs: no need to check return value of debugfs_create functions
nfsd: no need to check return value of debugfs_create functions
lib: 842: no need to check return value of debugfs_create functions
debugfs: provide pr_fmt() macro
debugfs: log errors when something goes wrong
drivers: s390/cio: Fix compilation warning about const qualifiers
drivers: Add generic helper to match by of_node
driver_find_device: Unify the match function with class_find_device()
bus_find_device: Unify the match callback with class_find_device
...
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms and conditions of the gnu general public license
version 2 as published by the free software foundation this program
is distributed in the hope it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 263 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.208660670@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Go over arch/x86/ and fix common typos in comments,
and a typo in an actual function argument name.
No change in functionality intended.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
On some BYT/CHT systems the SoC's P-Unit shares the I2C bus with the
kernel. The P-Unit has a semaphore for the PMIC bus which we can take to
block it from accessing the shared bus while the kernel wants to access it.
Currently we have the I2C-controller driver acquiring and releasing the
semaphore around each I2C transfer. There are 2 problems with this:
1) PMIC accesses often come in the form of a read-modify-write on one of
the PMIC registers, we currently release the P-Unit's PMIC bus semaphore
between the read and the write. If the P-Unit modifies the register during
this window?, then we end up overwriting the P-Unit's changes.
I believe that this is mostly an academic problem, but I'm not sure.
2) To safely access the shared I2C bus, we need to do 3 things:
a) Notify the GPU driver that we are starting a window in which it may not
access the P-Unit, since the P-Unit seems to ignore the semaphore for
explicit power-level requests made by the GPU driver
b) Make a pm_qos request to force all CPU cores out of C6/C7 since entering
C6/C7 while we hold the semaphore hangs the SoC
c) Finally take the P-Unit's PMIC bus semaphore
All 3 these steps together are somewhat expensive, so ideally if we have
a bunch of i2c transfers grouped together we only do this once for the
entire group.
Taking the read-modify-write on a PMIC register as example then ideally we
would only do all 3 steps once at the beginning and undo all 3 steps once
at the end.
For this we need to be able to take the semaphore from within e.g. the PMIC
opregion driver, yet we do not want to remove the taking of the semaphore
from the I2C-controller driver, as that is still necessary to protect many
other code-paths leading to accessing the shared I2C bus.
This means that we first have the PMIC driver acquire the semaphore and
then have the I2C controller driver trying to acquire it again.
To make this possible this commit does the following:
1) Move the semaphore code from being private to the I2C controller driver
into the generic iosf_mbi code, which already has other code to deal with
the shared bus so that it can be accessed outside of the I2C bus driver.
2) Rework the code so that it can be called multiple times nested, while
still blocking I2C accesses while e.g. the GPU driver has indicated the
P-Unit needs the bus through a iosf_mbi_punit_acquire() call.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
For race free unregistration drivers may need to acquire PMIC bus access
through iosf_mbi_punit_acquire() and then (un)register the notifier without
dropping the lock.
This commit adds an unlocked variant of
iosf_mbi_unregister_pmic_bus_access_notifier for this use case.
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171019111620.26761-2-hdegoede@redhat.com
Some drivers may need to acquire P-Unit managed resources from interrupt
context, where they cannot call iosf_mbi_punit_acquire().
This commit adds a notifier chain which allows a driver to get notified
(in a process context) before other drivers start accessing the PMIC bus,
so that the driver can acquire any resources, which it may need during
the window the other driver is accessing the PMIC, before hand.
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=155241
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: tagorereddy <tagore.chandan@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
One some systems the P-Unit accesses the PMIC to change various voltages
through the same bus as other kernel drivers use for e.g. battery
monitoring.
If a driver sends requests to the P-Unit which require the P-Unit to access
the PMIC bus while another driver is also accessing the PMIC bus various
bad things happen.
This commit adds a mutex to protect the P-Unit against simultaneous
accesses and 2 functions to lock / unlock this mutex.
Note on these systems the i2c-bus driver will request a sempahore from the
P-Unit for exclusive access to the PMIC bus when i2c drivers are accessing
it, but this does not appear to be sufficient, we still need to avoid
making certain P-Unit requests during the access window to avoid problems.
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=155241
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: tagorereddy <tagore.chandan@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170210102802.20898-2-hdegoede@redhat.com
- Move the static variables to one place
- Fix indentations in the header
- Correct comments
No functional change.
[ tglx: Massaged changelog ]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: David E . Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1436366709-17683-5-git-send-email-andriy.shevchenko@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The code checks the result of the first debugfs_create call several
times and fails to check the result of the subsequent calls due to
missing assigments.
Add the missing assignments and check only for !res because
debugfs_create() returns only NULL on error and not an encoded error
code.
[ tglx: Massaged changelog ]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: David E . Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1436366709-17683-3-git-send-email-andriy.shevchenko@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Move the driver to arch/x86/platform/intel since it is not a core
kernel code and it is related to many Intel SoCs from different
groups: Atom, MID, etc.
There is no functional change.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: David E . Box <david.e.box@linux.intel.com>
Link: http://lkml.kernel.org/r/1436366709-17683-2-git-send-email-andriy.shevchenko@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Hans de Goede