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Sverdlin" Cc: Alexander Sverdlin , Dong Aisheng , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate Date: Mon, 24 Apr 2023 10:08:51 +0200 Message-ID: <2679028.mvXUDI8C0e@steina-w> Organization: TQ-Systems GmbH In-Reply-To: <20230310130815.562418-1-alexander.sverdlin@siemens.com> References: <20230310130815.562418-1-alexander.sverdlin@siemens.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230424_010856_983005_008BE0A8 X-CRM114-Status: GOOD ( 26.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Am Freitag, 10. M=E4rz 2023, 14:08:15 CEST schrieb A. Sverdlin: > From: Alexander Sverdlin > = > 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 caus= ed > by the recursive feature of the "prepare_lock" (one clock instance is I2C > peripheral clock and another is pcf85063 RTC as clock provider): > = > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D > 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_it= er > #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 Reviewed-by: Alexander Stein Note: [1] needs to be applied as well in order to get rid of all the lockde= p = errors. [1] https://lore.kernel.org/linux-i2c/20230424080627.20564-1-alexander.stei= n@ew.tq-group.com/T/#u > --- > drivers/i2c/busses/i2c-imx-lpi2c.c | 33 +++++++++++++++++++++++++++--- > 1 file changed, 30 insertions(+), 3 deletions(-) > = > Changelog: > v3: fixed build error reported by kernel test robot > = > https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/ > 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 =3D data; > + struct lpi2c_imx_struct *lpi2c_imx =3D container_of(nb, > + struct = lpi2c_imx_struct, > + = clk_change_nb); > + > + if (action & POST_RATE_CHANGE) > + lpi2c_imx->rate_per =3D ndata->new_rate; > + > + return NOTIFY_OK; > +} > + > /* CLKLO =3D I2C_CLK_RATIO * CLKHI, SETHOLD =3D CLKHI, DATAVD =3D 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 =3D clk_get_rate(lpi2c_imx->clks[0].clk); > if (lpi2c_imx->mode =3D=3D HS || lpi2c_imx->mode =3D=3D ULTRA_FAST) > filt =3D 0; > else > filt =3D 2; > = > for (prescale =3D 0; prescale <=3D 7; prescale++) { > - clk_cycle =3D clk_rate / ((1 << prescale) * lpi2c_imx- >bitrate) > + clk_cycle =3D lpi2c_imx->rate_per / ((1 << prescale) * = lpi2c_imx->bitrate) > - 3 - (filt >> 1); > clkhi =3D (clk_cycle + I2C_CLK_RATIO) / (I2C_CLK_RATIO + 1); > clklo =3D 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 =3D lpi2c_imx_clk_change_cb; > + ret =3D 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 =3D 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); -- = TQ-Systems GmbH | M=FChlstra=DFe 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht M=FCnchen, HRB 105018 Gesch=E4ftsf=FChrer: Detlef Schneider, R=FCdiger Stahl, Stefan Schneider http://www.tq-group.com/ _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel