| Message ID | 20230628115824.3470880-1-alexander.sverdlin@siemens.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v5] i2c: lpi2c: cache peripheral clock rate | expand |
Am Mittwoch, 28. Juni 2023, 13:58:22 CEST schrieb A. Sverdlin: > 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 > ------------------------------------------------------ > .../2332 is trying to acquire lock: > ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x50/0xb0 > > but task is already holding lock: > ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: > i2c_adapter_lock_bus+0x2c/0x3c > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #2 (i2c_register_adapter){+.+.}-{3:3}: > lock_acquire+0x68/0x8c > rt_mutex_lock_nested+0x88/0xe0 > i2c_adapter_lock_bus+0x2c/0x3c > i2c_transfer+0x58/0x130 > regmap_i2c_read+0x64/0xb0 > _regmap_raw_read+0x114/0x440 > _regmap_bus_read+0x4c/0x84 > _regmap_read+0x6c/0x270 > regmap_read+0x54/0x80 > pcf85063_probe+0xec/0x4cc > i2c_device_probe+0x10c/0x350 > really_probe+0xc4/0x470 > __driver_probe_device+0x11c/0x190 > driver_probe_device+0x48/0x110 > __device_attach_driver+0xc4/0x160 > bus_for_each_drv+0x80/0xe0 > __device_attach+0xb0/0x1f0 > device_initial_probe+0x1c/0x2c > bus_probe_device+0xa4/0xb0 > device_add+0x398/0x8ac > device_register+0x28/0x40 > i2c_new_client_device+0x144/0x290 > of_i2c_register_devices+0x18c/0x230 > i2c_register_adapter+0x1dc/0x6b0 > __i2c_add_numbered_adapter+0x68/0xbc > i2c_add_adapter+0xb0/0xe0 > lpi2c_imx_probe+0x354/0x5e0 > platform_probe+0x70/0xec > really_probe+0xc4/0x470 > __driver_probe_device+0x11c/0x190 > driver_probe_device+0x48/0x110 > __device_attach_driver+0xc4/0x160 > bus_for_each_drv+0x80/0xe0 > __device_attach+0xb0/0x1f0 > device_initial_probe+0x1c/0x2c > bus_probe_device+0xa4/0xb0 > deferred_probe_work_func+0xa0/0xfc > process_one_work+0x2ac/0x6f4 > worker_thread+0x7c/0x47c > kthread+0x150/0x16c > ret_from_fork+0x10/0x20 > > -> #1 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}: > lock_acquire+0x68/0x8c > __mutex_lock+0x9c/0x4d0 > mutex_lock_nested+0x48/0x5c > regmap_lock_mutex+0x1c/0x30 > regmap_read+0x44/0x80 > pcf85063_clkout_recalc_rate+0x34/0x80 > __clk_register+0x520/0x880 > devm_clk_register+0x64/0xc4 > pcf85063_probe+0x24c/0x4cc > i2c_device_probe+0x10c/0x350 > really_probe+0xc4/0x470 > __driver_probe_device+0x11c/0x190 > driver_probe_device+0x48/0x110 > __device_attach_driver+0xc4/0x160 > bus_for_each_drv+0x80/0xe0 > __device_attach+0xb0/0x1f0 > device_initial_probe+0x1c/0x2c > bus_probe_device+0xa4/0xb0 > device_add+0x398/0x8ac > device_register+0x28/0x40 > i2c_new_client_device+0x144/0x290 > of_i2c_register_devices+0x18c/0x230 > i2c_register_adapter+0x1dc/0x6b0 > __i2c_add_numbered_adapter+0x68/0xbc > i2c_add_adapter+0xb0/0xe0 > lpi2c_imx_probe+0x354/0x5e0 > platform_probe+0x70/0xec > really_probe+0xc4/0x470 > __driver_probe_device+0x11c/0x190 > driver_probe_device+0x48/0x110 > __device_attach_driver+0xc4/0x160 > bus_for_each_drv+0x80/0xe0 > __device_attach+0xb0/0x1f0 > device_initial_probe+0x1c/0x2c > bus_probe_device+0xa4/0xb0 > deferred_probe_work_func+0xa0/0xfc > process_one_work+0x2ac/0x6f4 > worker_thread+0x7c/0x47c > kthread+0x150/0x16c > ret_from_fork+0x10/0x20 > > -> #0 (prepare_lock){+.+.}-{3:3}: > __lock_acquire+0x1298/0x20d0 > lock_acquire.part.0+0xf0/0x250 > lock_acquire+0x68/0x8c > __mutex_lock+0x9c/0x4d0 > mutex_lock_nested+0x48/0x5c > clk_prepare_lock+0x50/0xb0 > clk_get_rate+0x28/0x80 > lpi2c_imx_xfer+0xb0/0xa9c > __i2c_transfer+0x174/0xa80 > i2c_transfer+0x68/0x130 > regmap_i2c_read+0x64/0xb0 > _regmap_raw_read+0x114/0x440 > regmap_raw_read+0x19c/0x28c > regmap_bulk_read+0x1b8/0x244 > at24_read+0x14c/0x2c4 > nvmem_reg_read+0x2c/0x54 > bin_attr_nvmem_read+0x8c/0xbc > sysfs_kf_bin_read+0x74/0x94 > kernfs_fop_read_iter+0xb0/0x1d0 > new_sync_read+0xf0/0x184 > vfs_read+0x154/0x1f0 > ksys_read+0x70/0x100 > __arm64_sys_read+0x24/0x30 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0x68/0x124 > do_el0_svc+0x30/0x9c > el0_svc+0x54/0x110 > el0t_64_sync_handler+0xa4/0x130 > el0t_64_sync+0x1a0/0x1a4 > > 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+0x74/0x1d0 #1: ffff000010fe4400 > (kn->active#72){.+.+}-{0:0}, at: kernfs_fop_read_iter+0x7c/0x1d0 #2: > ffff0000110168e8 (&at24->lock){+.+.}-{3:3}, at: at24_read+0x8c/0x2c4 #3: > ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: > i2c_adapter_lock_bus+0x2c/0x3c > > stack backtrace: > CPU: 1 PID: 2332 Comm: ... Tainted: G O 5.15.71+... #1 > Hardware name: ... (DT) > Call trace: > dump_backtrace+0x0/0x1d4 > show_stack+0x20/0x2c > dump_stack_lvl+0x8c/0xb8 > dump_stack+0x18/0x34 > print_circular_bug+0x1f8/0x200 > check_noncircular+0x130/0x144 > __lock_acquire+0x1298/0x20d0 > lock_acquire.part.0+0xf0/0x250 > lock_acquire+0x68/0x8c > __mutex_lock+0x9c/0x4d0 > mutex_lock_nested+0x48/0x5c > clk_prepare_lock+0x50/0xb0 > clk_get_rate+0x28/0x80 > lpi2c_imx_xfer+0xb0/0xa9c > __i2c_transfer+0x174/0xa80 > i2c_transfer+0x68/0x130 > regmap_i2c_read+0x64/0xb0 > _regmap_raw_read+0x114/0x440 > regmap_raw_read+0x19c/0x28c > regmap_bulk_read+0x1b8/0x244 > at24_read+0x14c/0x2c4 > nvmem_reg_read+0x2c/0x54 > bin_attr_nvmem_read+0x8c/0xbc > sysfs_kf_bin_read+0x74/0x94 > kernfs_fop_read_iter+0xb0/0x1d0 > new_sync_read+0xf0/0x184 > vfs_read+0x154/0x1f0 > ksys_read+0x70/0x100 > __arm64_sys_read+0x24/0x30 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0x68/0x124 > do_el0_svc+0x30/0x9c > el0_svc+0x54/0x110 > el0t_64_sync_handler+0xa4/0x130 > el0t_64_sync+0x1a0/0x1a4 > > Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver") > Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com> > --- > Changelog: > v5: rebased onto Wolfram's i2c/for-next > v4: switched to atomic_t > included clk_rate_exclusive_get()/clk_rate_exclusive_put() > v3: fixed build error reported by kernel test robot <lkp@intel.com> The rebase still works as intended. Thanks and best regards, alexander > https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/ > v2: added clk_notifier as Alexander suggested > drivers/i2c/busses/i2c-imx-lpi2c.c | 47 +++++++++++++++++++++++++++--- > 1 file changed, 43 insertions(+), 4 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c > b/drivers/i2c/busses/i2c-imx-lpi2c.c index c3287c887c6f..02d376096707 > 100644 > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c > @@ -5,6 +5,7 @@ > * Copyright 2016 Freescale Semiconductor, Inc. > */ > > +#include <linux/atomic.h> > #include <linux/clk.h> > #include <linux/completion.h> > #include <linux/delay.h> > @@ -100,6 +101,8 @@ struct lpi2c_imx_struct { > __u8 *rx_buf; > __u8 *tx_buf; > struct completion complete; > + struct notifier_block clk_change_nb; > + atomic_t rate_per; > unsigned int msglen; > unsigned int delivered; > unsigned int block_data; > @@ -198,25 +201,39 @@ 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(nb, > + struct lpi2c_imx_struct, > + clk_change_nb); > + > + if (action & POST_RATE_CHANGE) > + atomic_set(&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, datavd; > - unsigned int clk_rate, clk_cycle, clkhi, clklo; > + unsigned int clk_cycle, clkhi, clklo; > 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) > - - 3 - (filt >> 1); > + clk_cycle = atomic_read(&lpi2c_imx->rate_per) / > + ((1 << prescale) * lpi2c_imx->bitrate) - 3 - > + (filt >> 1); > clkhi = DIV_ROUND_UP(clk_cycle, I2C_CLK_RATIO + 1); > clklo = clk_cycle - clkhi; > if (clklo < 64) > @@ -594,6 +611,28 @@ 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"); > + /* > + * Lock the clock rate to avoid rate change between clk_get_rate() and > + * atomic_set() > + */ > + ret = clk_rate_exclusive_get(lpi2c_imx->clks[0].clk); > + if (ret) { > + dev_err(&pdev->dev, "can't lock I2C peripheral clock rate\n"); > + return ret; > + } > + atomic_set(&lpi2c_imx->rate_per, clk_get_rate(lpi2c_imx- >clks[0].clk)); > + clk_rate_exclusive_put(lpi2c_imx->clks[0].clk); > + if (!atomic_read(&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);
diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c index c3287c887c6f..02d376096707 100644 --- a/drivers/i2c/busses/i2c-imx-lpi2c.c +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c @@ -5,6 +5,7 @@ * Copyright 2016 Freescale Semiconductor, Inc. */ +#include <linux/atomic.h> #include <linux/clk.h> #include <linux/completion.h> #include <linux/delay.h> @@ -100,6 +101,8 @@ struct lpi2c_imx_struct { __u8 *rx_buf; __u8 *tx_buf; struct completion complete; + struct notifier_block clk_change_nb; + atomic_t rate_per; unsigned int msglen; unsigned int delivered; unsigned int block_data; @@ -198,25 +201,39 @@ 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(nb, + struct lpi2c_imx_struct, + clk_change_nb); + + if (action & POST_RATE_CHANGE) + atomic_set(&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, datavd; - unsigned int clk_rate, clk_cycle, clkhi, clklo; + unsigned int clk_cycle, clkhi, clklo; 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) - - 3 - (filt >> 1); + clk_cycle = atomic_read(&lpi2c_imx->rate_per) / + ((1 << prescale) * lpi2c_imx->bitrate) - 3 - + (filt >> 1); clkhi = DIV_ROUND_UP(clk_cycle, I2C_CLK_RATIO + 1); clklo = clk_cycle - clkhi; if (clklo < 64) @@ -594,6 +611,28 @@ 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"); + /* + * Lock the clock rate to avoid rate change between clk_get_rate() and + * atomic_set() + */ + ret = clk_rate_exclusive_get(lpi2c_imx->clks[0].clk); + if (ret) { + dev_err(&pdev->dev, "can't lock I2C peripheral clock rate\n"); + return ret; + } + atomic_set(&lpi2c_imx->rate_per, clk_get_rate(lpi2c_imx->clks[0].clk)); + clk_rate_exclusive_put(lpi2c_imx->clks[0].clk); + if (!atomic_read(&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);