| Message ID | 20230309134302.74940-1-alexander.sverdlin@siemens.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | i2c: lpi2c: cache peripheral clock rate | expand |
Hi Alexander, Am Donnerstag, 9. März 2023, 14:43:01 CET 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 Which kernel is this? Mainline or downstream vendor kernel? > ------------------------------------------------------ > fs-value/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") > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com> > --- > drivers/i2c/busses/i2c-imx-lpi2c.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c > b/drivers/i2c/busses/i2c-imx-lpi2c.c index 188f2a36d2fd6..cf36f12b85573 > 100644 > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c > @@ -100,6 +100,7 @@ struct lpi2c_imx_struct { > __u8 *rx_buf; > __u8 *tx_buf; > struct completion complete; > + unsigned int rate_per; > unsigned int msglen; > unsigned int delivered; > unsigned int block_data; > @@ -202,20 +203,19 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct > *lpi2c_imx) 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 +588,12 @@ static int lpi2c_imx_probe(struct platform_device > *pdev) if (ret) > return ret; > > + 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; > + } > + What if the peripheral clock rate changes? I guess a notifier similar to 90ad2cbe88c2 ("i2c: imx: use clk notifier for rate changes") should be added as well. Best regards, Alexander > pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT); > pm_runtime_use_autosuspend(&pdev->dev); > pm_runtime_get_noresume(&pdev->dev);
Hi! On Thu, 2023-03-09 at 15:37 +0100, Alexander Stein wrote: > 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 > > Which kernel is this? Mainline or downstream vendor kernel? found and tested on downstream vendor kernel. [...] > > > What if the peripheral clock rate changes? I guess a notifier similar > to > 90ad2cbe88c2 ("i2c: imx: use clk notifier for rate changes") should > be added > as well. > Good point! Thank you for the hint!
diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c index 188f2a36d2fd6..cf36f12b85573 100644 --- a/drivers/i2c/busses/i2c-imx-lpi2c.c +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c @@ -100,6 +100,7 @@ struct lpi2c_imx_struct { __u8 *rx_buf; __u8 *tx_buf; struct completion complete; + unsigned int rate_per; unsigned int msglen; unsigned int delivered; unsigned int block_data; @@ -202,20 +203,19 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx) 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 +588,12 @@ static int lpi2c_imx_probe(struct platform_device *pdev) if (ret) return ret; + 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);