From patchwork Mon Apr 22 11:36:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Alexander Stein X-Patchwork-Id: 13638412 Received: from mx1.tq-group.com (mx1.tq-group.com [93.104.207.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E2D21465A2 for ; Mon, 22 Apr 2024 11:36:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.104.207.81 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713785801; cv=none; b=lLO09d0LrYCVF8MjiLEu+Dq84e1BtOGSFy/n3YnuVn15ARrQHBaB3NE69G4h/KJXktUuV7hGu8PgqF0D4ekX04GQzmJRFXRfvICz0znheDjJ1uujt2S9HNSsMQMsZWSf1SVA3E6PykS6Qnya6emYVz4G8hVQEuwq52I16cnlGe4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713785801; c=relaxed/simple; bh=ItdicYmLWZdbJ4/E+0SqxN1tOW9mkHu6tubEIWymiTo=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version:Content-Type; b=jSofavLpobNvNTLiDU3tUqxWSiwQNLOd2e7YMuvPXm6L4CYskbw7SymLRGo3Fr62vgk93t4dxCefUhOgzRpA8DrqohnE/nKNo9A0qqjr+jMcNrIiLFFVsVxaCrkmuUkOnEE/KqVXry6pT7vVptcxNbOiJcwGF0BZI1AhpFgH/4s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ew.tq-group.com; spf=pass smtp.mailfrom=ew.tq-group.com; dkim=pass (2048-bit key) header.d=tq-group.com header.i=@tq-group.com header.b=P4aoMHOs; dkim=fail (0-bit key) header.d=ew.tq-group.com header.i=@ew.tq-group.com header.b=jPo7Kp3i reason="key not found in DNS"; arc=none smtp.client-ip=93.104.207.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ew.tq-group.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ew.tq-group.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=tq-group.com header.i=@tq-group.com header.b="P4aoMHOs"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=ew.tq-group.com header.i=@ew.tq-group.com header.b="jPo7Kp3i" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1713785797; x=1745321797; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=a8tmUfcLbDKINV4lHr1PNpryxyZNz/7RC/mYXxPwibE=; b=P4aoMHOs3qnnOcMnTAupO0DLpd8FLXQZBzVcNORzQnFBGH8CNHfuOoPc Ka0IP6KH29rHY6Nr9lCdfGVLPLZRk2FfTgYybi8N73Vc4uEsQd7XTCPur P/6olANW891IhEI0SHZMX7aQ7JLUoCvQuPBejYWh59rhNnwAfjoXN0FWa yY9w19HSmp0ndwBQWB6AcZb9XbfhDzhQAVxVfj9yFQOK9xhYFpmxRfVGw By+CEUBkJAK8vlte1bNiBTbMqtX9OjenOCzCnYUJlTHrW3YLy8Scw1KT2 qMVIDKzSb4zm7BXh1krly1RpJMmWzTAzWJl5h/XoAgEsQtRbGew6wuGlp Q==; X-IronPort-AV: E=Sophos;i="6.07,220,1708383600"; d="scan'208";a="36541302" Received: from vmailcow01.tq-net.de ([10.150.86.48]) by mx1.tq-group.com with ESMTP; 22 Apr 2024 13:36:34 +0200 Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id E08EE160AEF; Mon, 22 Apr 2024 13:36:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ew.tq-group.com; s=dkim; t=1713785790; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=a8tmUfcLbDKINV4lHr1PNpryxyZNz/7RC/mYXxPwibE=; b=jPo7Kp3ibDT+vTxxqzArMmj6CmwpJ7g3V7e3im9iqmjqM1dBgGoVXLfeMQ+uQNyHiV16+F Xh6Kujzotm/mBwjLTyI5q54L+4dAW8h+PyoZWqezTsuogWqKX/DWVtfuLxsfklbNUHL/bu NAcczu1W2rejJjDZsapvY8zyjzGbyz/VINKkZKVB1fWM1BlZGQN6raq2fdOS2sOjRrC8rv 0ai1XFjyWlX9k4jEK5QsGV2pYc4U+g9BlxIdjFiCk9UUdIYw0+sUdMK3TzQA4EJ6uvh/iP Vb3YKvXUX/ayvFAGxqVZHg3dJ3Sg1gFYHIYb9PQFd3kQwimWvSpzrCIy5KbuQg== From: Alexander Stein To: Dong Aisheng , Andi Shyti , Shawn Guo , Sascha Hauer , Fabio Estevam , Pengutronix Kernel Team Cc: Alexander Stein , NXP Linux Team , linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , imx@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v3 1/1] i2c: lpi2c: Avoid calling clk_get_rate during transfer Date: Mon, 22 Apr 2024 13:36:29 +0200 Message-Id: <20240422113629.1629891-1-alexander.stein@ew.tq-group.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Last-TLS-Session-Version: TLSv1.3 Instead of repeatedly calling clk_get_rate for each transfer, lock the clock rate and cache the value. A deadlock has been observed while adding tlv320aic32x4 audio codec to the system. When this clock provider adds its clock, the clk mutex is locked already, it needs to access i2c, which in return needs the mutex for clk_get_rate as well. Signed-off-by: Alexander Stein Reviewed-by: Uwe Kleine-König Reviewed-by: Andi Shyti --- This is an alternative, lightweight approach replacing the patch [1]. The issue to address is still removing the call to clk_get_rate() during each transfer, which might reuslt in a deadlock. lockdep also complains about this call chain. The dependency from v2 has already been merged in commit b0cde62e4c548 ("clk: Add a devm variant of clk_rate_exclusive_get()"). Instead of adding a clock notifier, lock the peripheral clock rate and cache the peripheral clock rate. Currently LPI2C is available in the following SoC: * i.MX7ULP * i.MX8ULP * i.MX8DXL * i.MX8X * i.MX8 * i.MX93 Additionally I expect both i.MX91 and i.MX95 to also use this driver. This patch assumes the parent clock rate never changes. This is apparently true for i.MX93 as each I2C has it's own lpi2c*_root clock. On i.MX8 and i.MX8X clocks are managed by SCU with it's own dedicated firmware. I can't say if the clock never changes though. I have no idea about the other SoC. Changes in v3: * Rebased to next-20240422 Changes in v2: * Removed redundent clk_rate check in lpi2c_imx_config (I opted to keep the local variable to not extent the calculation code lines) * Collected R-b Best regards, Alexander [1] https://lore.kernel.org/all/20240110120556.519800-1-alexander.stein@ew.tq-group.com/ drivers/i2c/busses/i2c-imx-lpi2c.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c index 6d72e4e126dde..36e8f6196a87b 100644 --- a/drivers/i2c/busses/i2c-imx-lpi2c.c +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c @@ -99,6 +99,7 @@ struct lpi2c_imx_struct { __u8 *rx_buf; __u8 *tx_buf; struct completion complete; + unsigned long rate_per; unsigned int msglen; unsigned int delivered; unsigned int block_data; @@ -212,9 +213,7 @@ static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx) lpi2c_imx_set_mode(lpi2c_imx); - clk_rate = clk_get_rate(lpi2c_imx->clks[0].clk); - if (!clk_rate) - return -EINVAL; + clk_rate = lpi2c_imx->rate_per; if (lpi2c_imx->mode == HS || lpi2c_imx->mode == ULTRA_FAST) filt = 0; @@ -611,6 +610,20 @@ static int lpi2c_imx_probe(struct platform_device *pdev) if (ret) return ret; + /* + * Lock the parent clock rate to avoid getting parent clock upon + * each transfer + */ + ret = devm_clk_rate_exclusive_get(&pdev->dev, lpi2c_imx->clks[0].clk); + if (ret) + return dev_err_probe(&pdev->dev, ret, + "can't lock I2C peripheral clock rate\n"); + + lpi2c_imx->rate_per = clk_get_rate(lpi2c_imx->clks[0].clk); + if (!lpi2c_imx->rate_per) + return dev_err_probe(&pdev->dev, -EINVAL, + "can't get I2C peripheral clock rate\n"); + pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT); pm_runtime_use_autosuspend(&pdev->dev); pm_runtime_get_noresume(&pdev->dev);