diff mbox series

[v2] i2c: lpi2c: cache peripheral clock rate

Message ID 20230310112605.476922-1-alexander.sverdlin@siemens.com
State Superseded
Headers show
Series [v2] i2c: lpi2c: cache peripheral clock rate | expand

Commit Message

A. Sverdlin March 10, 2023, 11:26 a.m. UTC 
From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

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 <alexander.sverdlin@siemens.com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

Changelog:
v2: added clk_notifier as Alexander suggested

Comments

kernel test robot March 10, 2023, 12:37 p.m. UTC | #1 
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/20230310/202303102010.pAv56wKs-lkp@intel.com/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 <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/

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
diff mbox series

Patch

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);