From mboxrd@z Thu Jan 1 00:00:00 1970 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 7030EC7EE24 for ; Wed, 31 May 2023 07:38:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234646AbjEaHh7 (ORCPT ); Wed, 31 May 2023 03:37:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232229AbjEaHh4 (ORCPT ); Wed, 31 May 2023 03:37:56 -0400 Received: from mx1.tq-group.com (mx1.tq-group.com [93.104.207.81]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 432A4C0; Wed, 31 May 2023 00:37:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1685518673; x=1717054673; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=A0CMn3ra+DbJMLgi7YsDqMe0dIiAqyIrPwvqTLxPn5s=; b=SrrDp1E8xKLkWmHr/2MvOpcs9iO3W0LcRp23cG3Xr0qSKbjvTDWsTRjA DftP3t2SsLnjiffWrODO/6FaluUqt73zPJjCchNOYTAwMJnK8G58cuJNz 4pd4WHVC1RHpJYHeqoMlmA6GDCv+euTz0DzItgfnulujkBEGJ24TPLIu9 vIqK/ufzQ50RBW9IES5YI+PAiXvVdBkfN+TJCOMEHGR+NoiFKnXRxVa0I owWx66DrdjqGdxwtFQJo+N9kBEVCQeIEMG7yArYDzLMU3HuLo4LKbxa82 hINE5H/baXvJpTJvZO4FwU12BuC/RoBW6cEmHRpYo5rVRvtt+BuUgKjb1 g==; X-IronPort-AV: E=Sophos;i="6.00,205,1681164000"; d="scan'208";a="31185173" Received: from unknown (HELO tq-pgp-pr1.tq-net.de) ([192.168.6.15]) by mx1-pgp.tq-group.com with ESMTP; 31 May 2023 09:37:51 +0200 Received: from mx1.tq-group.com ([192.168.6.7]) by tq-pgp-pr1.tq-net.de (PGP Universal service); Wed, 31 May 2023 09:37:51 +0200 X-PGP-Universal: processed; by tq-pgp-pr1.tq-net.de on Wed, 31 May 2023 09:37:51 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1685518671; x=1717054671; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=A0CMn3ra+DbJMLgi7YsDqMe0dIiAqyIrPwvqTLxPn5s=; b=L47xWWOUZsHZBPC6ajue2Ic1e/3WGqo3/Sb2v4d/xJYrGXc/Sn7GG/F9 vX0GPfKdpQxC8A6VinKALtfxBWVGyORvsCJDBn5Lmapls7ircUtEDLuBu iHXSuwAr6Zgl8pUHpRwianTkssx/PL71LC+i3myFStM/D3d3tf2zCnxWs bc/bSQiDhuX9KWsonrQHxL5Px1LJO5aSqcUX4qNR7xg9OpMnDRT+OSM+H hGY/PPkcVo8oOKO7II/PvcfyudGqKpOQj/4GSV+mPm9bMau7xcpMcwvWj XC+Ca8Hrhk41fRPETFDa8OihDLg1we40DzXRzBM/7F2Kx7qSRqOhgSiOU Q==; X-IronPort-AV: E=Sophos;i="6.00,205,1681164000"; d="scan'208";a="31185172" Received: from vtuxmail01.tq-net.de ([10.115.0.20]) by mx1.tq-group.com with ESMTP; 31 May 2023 09:37:51 +0200 Received: from steina-w.localnet (unknown [10.123.53.21]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by vtuxmail01.tq-net.de (Postfix) with ESMTPSA id 1CCF1280099; Wed, 31 May 2023 09:37:51 +0200 (CEST) From: Alexander Stein To: NXP Linux Team , "A. 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 v4] i2c: lpi2c: cache peripheral clock rate Date: Wed, 31 May 2023 09:37:50 +0200 Message-ID: <8230613.T7Z3S40VBb@steina-w> Organization: TQ-Systems GmbH In-Reply-To: <20230515201844.215253-1-alexander.sverdlin@siemens.com> References: <20230515201844.215253-1-alexander.sverdlin@siemens.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Am Montag, 15. Mai 2023, 22:18:44 CEST schrieb A. Sverdlin: > From: Alexander Sverdlin >=20 > 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): Looks good to me. Thanks. Reviewed-by: Alexander Stein > =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 > ------------------------------------------------------ > .../2332 is trying to acquire lock: > ffff8000096cae08 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x50/0x= b0 >=20 > but task is already holding lock: > ffff000011021100 (i2c_register_adapter){+.+.}-{3:3}, at: > i2c_adapter_lock_bus+0x2c/0x3c >=20 > which lock already depends on the new lock. >=20 > the existing dependency chain (in reverse order) is: >=20 > -> #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 >=20 > -> #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 >=20 > -> #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 >=20 > other info that might help us debug this: >=20 > Chain exists of: > prepare_lock --> rtc_pcf85063:560:(&config->regmap)->lock --> > i2c_register_adapter >=20 > Possible unsafe locking scenario: >=20 > CPU0 CPU1 > ---- ---- > lock(i2c_register_adapter); > =20 > lock(rtc_pcf85063:560:(&config->regmap)->lock); lock(i2c_register_adapter= ); > lock(prepare_lock); >=20 > *** DEADLOCK *** >=20 > 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 >=20 > 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 >=20 > Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver") > Signed-off-by: Alexander Sverdlin > --- > Changelog: > v4: switched to atomic_t > included clk_rate_exclusive_get()/clk_rate_exclusive_put() > v3: fixed build error reported by kernel test robot > =20 > https://lore.kernel.org/oe-kbuild-all/202303102010.pAv56wKs-lkp@intel.com/ > v2: added clk_notifier as Alexander suggested >=20 > drivers/i2c/busses/i2c-imx-lpi2c.c | 47 +++++++++++++++++++++++++++--- > 1 file changed, 43 insertions(+), 4 deletions(-) >=20 > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c > b/drivers/i2c/busses/i2c-imx-lpi2c.c index 1af0a637d7f1..b31d29d684fa > 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. > */ >=20 > +#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); > } >=20 > +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=20 lpi2c_imx_struct, > + =20 clk_change_nb); > + > + if (action & POST_RATE_CHANGE) > + atomic_set(&lpi2c_imx->rate_per, 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; >=20 > lpi2c_imx_set_mode(lpi2c_imx); >=20 > - 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; >=20 > for (prescale =3D 0; prescale <=3D 7; prescale++) { > - clk_cycle =3D clk_rate / ((1 << prescale) * lpi2c_imx- >bitrate) > - - 3 - (filt >> 1); > + clk_cycle =3D atomic_read(&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; > if (clklo < 64) > @@ -594,6 +611,28 @@ static int lpi2c_imx_probe(struct platform_device > *pdev) if (ret) > return ret; >=20 > + 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=20 notifier\n"); > + /* > + * Lock the clock rate to avoid rate change between clk_get_rate()=20 and > + * atomic_set() > + */ > + ret =3D clk_rate_exclusive_get(lpi2c_imx->clks[0].clk); > + if (ret) { > + dev_err(&pdev->dev, "can't lock I2C peripheral clock=20 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=20 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); =2D-=20 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/