LinuxLists.cc - [PATCH v2] i2c: lpi2c: cache peripheral clock rate

2023-03-10 11:26:20

Subject: [PATCH v2] i2c: lpi2c: cache peripheral clock rate

From: Alexander Sverdlin <[email protected]>

One of the reasons to do it is to save some CPU cycles on cpu_freq_get()
under mutex. The second reason if the (false-positive) lockdep splat caused
by the recursive feature of the "prepare_lock" (one clock instance is I2C
peripheral clock and another is pcf85063 RTC as clock provider):

======================================================
WARNING: possible circular locking dependency detected
5.15.71+... #1 Tainted: G O
------------------------------------------------------
fs-value/2332 is trying to acquire lock:
ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock

but task is already holding lock:
ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: i2c_adapter_lock_bus

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (i2c_register_adapter){+.+.}-{3:3}:
lock_acquire
rt_mutex_lock_nested
i2c_adapter_lock_bus
i2c_transfer
regmap_i2c_read
_regmap_raw_read
_regmap_bus_read
_regmap_read
regmap_read
pcf85063_probe
i2c_device_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
device_add
device_register
i2c_new_client_device
of_i2c_register_devices
i2c_register_adapter
__i2c_add_numbered_adapter
i2c_add_adapter
lpi2c_imx_probe
platform_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
deferred_probe_work_func
process_one_work
worker_thread
kthread
ret_from_fork

-> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
lock_acquire
__mutex_lock
mutex_lock_nested
regmap_lock_mutex
regmap_read
pcf85063_clkout_recalc_rate
__clk_register
devm_clk_register
pcf85063_probe
i2c_device_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
device_add
device_register
i2c_new_client_device
of_i2c_register_devices
i2c_register_adapter
__i2c_add_numbered_adapter
i2c_add_adapter
lpi2c_imx_probe
platform_probe
really_probe
__driver_probe_device
driver_probe_device
__device_attach_driver
bus_for_each_drv
__device_attach
device_initial_probe
bus_probe_device
deferred_probe_work_func
process_one_work
worker_thread
kthread
ret_from_fork

-> #0 (prepare_lock){+.+.}-{3:3}:
__lock_acquire
lock_acquire.part.0
lock_acquire
__mutex_lock
mutex_lock_nested
clk_prepare_lock
clk_get_rate
lpi2c_imx_xfer
__i2c_transfer
i2c_transfer
regmap_i2c_read
_regmap_raw_read
regmap_raw_read
regmap_bulk_read
at24_read
nvmem_reg_read
bin_attr_nvmem_read
sysfs_kf_bin_read
kernfs_fop_read_iter
new_sync_read
vfs_read
ksys_read
__arm64_sys_read
invoke_syscall
...

other info that might help us debug this:

Chain exists of:
prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock --> i2c_register_adapter

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(i2c_register_adapter);
lock(rtc_pcf85063:560:(&config->regmap)->lock);
lock(i2c_register_adapter);
lock(prepare_lock);

*** DEADLOCK ***

4 locks held by .../2332:
#0: ffff0000146eb288 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_read_iter
#1: ffff000010fe4400 (kn->active#72){.+.+}-{0:0}, at: kernfs_fop_read_iter
#2: ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read
#3: ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: i2c_adapter_lock_bus

stack backtrace:
CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1
Hardware name: ... (DT)
Call trace:
dump_backtrace
show_stack
dump_stack_lvl
dump_stack
print_circular_bug
check_noncircular
__lock_acquire
lock_acquire.part.0
lock_acquire
__mutex_lock
mutex_lock_nested
clk_prepare_lock
clk_get_rate
lpi2c_imx_xfer
__i2c_transfer
i2c_transfer
regmap_i2c_read
_regmap_raw_read
regmap_raw_read
regmap_bulk_read
at24_read
nvmem_reg_read
bin_attr_nvmem_read
sysfs_kf_bin_read
kernfs_fop_read_iter
new_sync_read
vfs_read
ksys_read
__arm64_sys_read
invoke_syscall
...

Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
Signed-off-by: Alexander Sverdlin <[email protected]>
---
drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)

Changelog:
v2: added clk_notifier as Alexander suggested

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 188f2a36d2fd6..5f1d1d4e018bd 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -100,6 +100,8 @@ struct lpi2c_imx_struct {
__u8 *rx_buf;
__u8 *tx_buf;
struct completion complete;
+ struct notifier_block clk_change_nb;
+ unsigned int rate_per;
unsigned int msglen;
unsigned int delivered;
unsigned int block_data;
@@ -198,24 +200,37 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
} while (1);
}

+static int lpi2c_imx_clk_change_cb(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct clk_notifier_data *ndata = data;
+ struct lpi2c_imx_struct *lpi2c_imx = container_of(&ndata->clk,
+ struct lpi2c_imx_struct,
+ clk_per);
+
+ if (action & POST_RATE_CHANGE)
+ lpi2c_imx->rate_per = ndata->new_rate;
+
+ return NOTIFY_OK;
+}
+
/* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
{
u8 prescale, filt, sethold, clkhi, clklo, datavd;
- unsigned int clk_rate, clk_cycle;
+ unsigned int clk_cycle;
enum lpi2c_imx_pincfg pincfg;
unsigned int temp;

lpi2c_imx_set_mode(lpi2c_imx);

- clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk);
if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST)
filt = 0;
else
filt = 2;

for (prescale = 0; prescale <= 7; prescale++) {
- clk_cycle = clk_rate / ((1 << prescale) * lpi2c_imx->bitrate)
+ clk_cycle = lpi2c_imx->rate_per / ((1 << prescale) * lpi2c_imx->bitrate)
- 3 - (filt >> 1);
clkhi = (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1);
clklo = clk_cycle - clkhi;
@@ -588,6 +603,18 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
if (ret)
return ret;

+ lpi2c_imx->clk_change_nb.notifier_call = lpi2c_imx_clk_change_cb;
+ ret = devm_clk_notifier_register(&pdev->dev, lpi2c_imx->clks[0].clk,
+ &lpi2c_imx->clk_change_nb);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "can't register peripheral clock notifier\n");
+ lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk);
+ if (!lpi2c_imx->rate_per) {
+ dev_err(&pdev->dev, "can't get I2C peripheral clock rate\n");
+ return -EINVAL;
+ }
+
pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_get_noresume(&pdev->dev);
--
2.34.1

2023-03-10 12:39:04

by kernel test robot

[permalink] [raw]

Subject: Re: [PATCH v2] i2c: lpi2c: cache peripheral clock rate

Hi Sverdlin,

I love your patch! Yet something to improve:

[auto build test ERROR on wsa/i2c/for-next]
[also build test ERROR on linus/master v6.3-rc1 next-20230310]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/A-Sverdlin/i2c-lpi2c-cache-peripheral-clock-rate/20230310-192720
base: https://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git i2c/for-next
patch link: https://lore.kernel.org/r/20230310112605.476922-1-alexander.sverdlin%40siemens.com
patch subject: [PATCH v2] i2c: lpi2c: cache peripheral clock rate
config: riscv-allmodconfig (https://download.01.org/0day-ci/archive/20230310/[email protected]/config)
compiler: riscv64-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/aa3870869fbb164ebdc12f412c07c66f1d7cdf2d
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review A-Sverdlin/i2c-lpi2c-cache-peripheral-clock-rate/20230310-192720
git checkout aa3870869fbb164ebdc12f412c07c66f1d7cdf2d
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/i2c/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[email protected]>
| Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All errors (new ones prefixed by >>):

In file included from include/linux/container_of.h:5,
from include/linux/kernel.h:21,
from include/linux/clk.h:13,
from drivers/i2c/busses/i2c-imx-lpi2c.c:8:
drivers/i2c/busses/i2c-imx-lpi2c.c: In function 'lpi2c_imx_clk_change_cb':
>> include/linux/container_of.h:20:54: error: 'struct lpi2c_imx_struct' has no member named 'clk_per'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~
include/linux/build_bug.h:78:56: note: in definition of macro '__static_assert'
78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
| ^~~~
include/linux/container_of.h:20:9: note: in expansion of macro 'static_assert'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~~~~~~~~~~~~
include/linux/container_of.h:20:23: note: in expansion of macro '__same_type'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~~~~~~~~~~
drivers/i2c/busses/i2c-imx-lpi2c.c:207:46: note: in expansion of macro 'container_of'
207 | struct lpi2c_imx_struct *lpi2c_imx = container_of(&ndata->clk,
| ^~~~~~~~~~~~
include/linux/compiler_types.h:338:27: error: expression in static assertion is not an integer
338 | #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:78:56: note: in definition of macro '__static_assert'
78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
| ^~~~
include/linux/container_of.h:20:9: note: in expansion of macro 'static_assert'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~~~~~~~~~~~~
include/linux/container_of.h:20:23: note: in expansion of macro '__same_type'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~~~~~~~~~~
drivers/i2c/busses/i2c-imx-lpi2c.c:207:46: note: in expansion of macro 'container_of'
207 | struct lpi2c_imx_struct *lpi2c_imx = container_of(&ndata->clk,
| ^~~~~~~~~~~~
In file included from include/uapi/linux/posix_types.h:5,
from include/uapi/linux/types.h:14,
from include/linux/types.h:6,
from include/linux/kasan-checks.h:5,
from include/asm-generic/rwonce.h:26,
from ./arch/riscv/include/generated/asm/rwonce.h:1,
from include/linux/compiler.h:247,
from include/linux/err.h:5,
from include/linux/clk.h:12:
>> include/linux/stddef.h:16:33: error: 'struct lpi2c_imx_struct' has no member named 'clk_per'
16 | #define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER)
| ^~~~~~~~~~~~~~~~~~
include/linux/container_of.h:23:28: note: in expansion of macro 'offsetof'
23 | ((type *)(__mptr - offsetof(type, member))); })
| ^~~~~~~~
drivers/i2c/busses/i2c-imx-lpi2c.c:207:46: note: in expansion of macro 'container_of'
207 | struct lpi2c_imx_struct *lpi2c_imx = container_of(&ndata->clk,
| ^~~~~~~~~~~~

vim +20 include/linux/container_of.h

d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 9
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 10 /**
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 11 * container_of - cast a member of a structure out to the containing structure
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 12 * @ptr: the pointer to the member.
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 13 * @type: the type of the container struct this is embedded in.
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 14 * @member: the name of the member within the struct.
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 15 *
7376e561fd2e01 Sakari Ailus 2022-10-24 16 * WARNING: any const qualifier of @ptr is lost.
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 17 */
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 18 #define container_of(ptr, type, member) ({ \
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 19 void *__mptr = (void *)(ptr); \
e1edc277e6f6df Rasmus Villemoes 2021-11-08 @20 static_assert(__same_type(*(ptr), ((type *)0)->member) || \
e1edc277e6f6df Rasmus Villemoes 2021-11-08 21 __same_type(*(ptr), void), \
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 22 "pointer type mismatch in container_of()"); \
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 23 ((type *)(__mptr - offsetof(type, member))); })
d2a8ebbf8192b8 Andy Shevchenko 2021-11-08 24

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

2023-03-10 12:48:28

by kernel test robot

[permalink] [raw]