From patchwork Thu Mar 9 13:43:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "A. Sverdlin" X-Patchwork-Id: 661303 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 C8EC4C6FD1F for ; Thu, 9 Mar 2023 13:43:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230248AbjCINn0 (ORCPT ); Thu, 9 Mar 2023 08:43:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231211AbjCINnO (ORCPT ); Thu, 9 Mar 2023 08:43:14 -0500 Received: from mta-65-225.siemens.flowmailer.net (mta-65-225.siemens.flowmailer.net [185.136.65.225]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C10531CBE7 for ; Thu, 9 Mar 2023 05:43:09 -0800 (PST) Received: by mta-65-225.siemens.flowmailer.net with ESMTPSA id 202303091343061f1f673d7c34af0d72 for ; Thu, 09 Mar 2023 14:43:06 +0100 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=LWWKSwja5zpZiSyAbqGvPA3W0gLM9JY5S2eHp533JBM=; b=Nb4H6nKWf5vNXd8NWPi/hVRmqfXPnDDgQ2IE8j8xcJpvFWkAeqEuOTqBkLyf/irAEMHwFp IlAX383PnSPfy3MkxMlvvwFK589VAzVepM5sL2zJmn4KITmd4vNhE18h3uwvvDVZHlyeTyw2 BiRd8tfUQFI/w6XlNTpfT4YnHIIxE=; From: "A. Sverdlin" To: NXP Linux Team 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: [PATCH] i2c: lpi2c: cache peripheral clock rate Date: Thu, 9 Mar 2023 14:43:01 +0100 Message-Id: <20230309134302.74940-1-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 ------------------------------------------------------ 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 --- 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; + } + pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT); pm_runtime_use_autosuspend(&pdev->dev); pm_runtime_get_noresume(&pdev->dev);