From patchwork Wed Jun 28 11:58:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "A. Sverdlin" X-Patchwork-Id: 697557 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39E89EB64D7 for ; Wed, 28 Jun 2023 11:58:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231770AbjF1L6i (ORCPT ); Wed, 28 Jun 2023 07:58:38 -0400 Received: from mta-64-226.siemens.flowmailer.net ([185.136.64.226]:51427 "EHLO mta-64-226.siemens.flowmailer.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229456AbjF1L6d (ORCPT ); Wed, 28 Jun 2023 07:58:33 -0400 Received: by mta-64-226.siemens.flowmailer.net with ESMTPSA id 2023062811583016106698fcb41a2b12 for ; Wed, 28 Jun 2023 13:58:30 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm1; d=siemens.com; i=alexander.sverdlin@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc; bh=i0BPABto0TdvB4oZgsYrJLQ1HUjeI6OR9dmKPeyNzmE=; b=GW2rRSamvJiVBDB/WWPAxzmqMSwWusUsMA3Sj9S0MhM3CI8sSBoTZTJjb2dP6sQ9lyosON 7RduDS9rdPNt3pGF5rouDfzIIbdm4PNRj62U0PiD4qV/6xnqgm58KgvIRyUqVcutyt8YzJi/ Fk3oWPxxycd110KPAVxXF1p6hlUOw=; From: "A. Sverdlin" To: NXP Linux Team Cc: Alexander Sverdlin , Alexander Stein , 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: [PATCH v5] i2c: lpi2c: cache peripheral clock rate Date: Wed, 28 Jun 2023 13:58:22 +0200 Message-ID: <20230628115824.3470880-1-alexander.sverdlin@siemens.com> MIME-Version: 1.0 X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-456497:519-21489:flowmailer Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org 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 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 Signed-off-by: Alexander Sverdlin --- 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 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 #include #include #include @@ -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);