From patchwork Mon Apr 11 13:21:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: AngeloGioacchino Del Regno X-Patchwork-Id: 559795 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 EF4C3C433EF for ; Mon, 11 Apr 2022 13:21:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244119AbiDKNXk (ORCPT ); Mon, 11 Apr 2022 09:23:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240292AbiDKNXj (ORCPT ); Mon, 11 Apr 2022 09:23:39 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA91C2DDD; Mon, 11 Apr 2022 06:21:23 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: kholk11) with ESMTPSA id AA1D01F43EE0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1649683282; bh=2XhjOAxBOcasYg+yweGriOPt9i9ytqipWQNUM8ynUvs=; h=From:To:Cc:Subject:Date:From; b=GlHY/c+UwUUnZic1hLXNOsUXuJA7JdhWK31rInpVFJM7ADsSviC67DbQh/KeHNaNu 04t0wWurRsxs+2JQKNd7i14Q4sd4/uHkz3zJDavOOz4Syu/ZJNXtxmIEY/ZWMlJFho /v6ZSEMXjXaJ9f9j4DzFyJ7ma2hvTrw8WwCCcrZkpBTnheUvTnSmUiEAWAKZcUaoO4 /4v+p19Rrq/ymrpCOB/TcVhjEoJRPS0Ab46NJJWzP4L260hXYpUWho5k8OztDZijD0 Hwutt+gMqvqWurwlMKub8zVji6VZGmZqXtHAj69Kf9zZj0hnAxxcRtET80mtOvTjNd QzflcQIQFOzFw== From: AngeloGioacchino Del Regno To: qii.wang@mediatek.com Cc: matthias.bgg@gmail.com, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, wsa@kernel.org, nfraprado@collabora.com, kernel@collabora.com, AngeloGioacchino Del Regno Subject: [PATCH v2] i2c: mediatek: Optimize master_xfer() and avoid circular locking Date: Mon, 11 Apr 2022 15:21:07 +0200 Message-Id: <20220411132107.136369-1-angelogioacchino.delregno@collabora.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Especially (but not only) during probe, it may happen that multiple devices are communicating via i2c (or multiple i2c busses) and sometimes while others are probing asynchronously. For example, a Cr50 TPM may be filling entropy (or userspace may be reading random data) while the rt5682 (i2c) codec driver reads/sets some registers, like while getting/setting a clock's rate, which happens both during probe and during system operation. In this driver, the mtk_i2c_transfer() function (which is the i2c .master_xfer() callback) was granularly managing the clocks by performing a clk_bulk_prepare_enable() to start them and its inverse. This is not only creating possible circular locking dependencies in the some cases (like former explanation), but it's also suboptimal, as clk_core prepare/unprepare operations are using mutex locking, which creates a bit of unwanted overhead (for example, i2c trackpads will call master_xfer() every few milliseconds!). With this commit, we avoid both the circular locking and additional overhead by changing how we handle the clocks in this driver: - Prepare the clocks during probe (and PM resume) - Enable/disable clocks in mtk_i2c_transfer() - Unprepare the clocks only for driver removal (and PM suspend) For the sake of providing a full explanation: during probe, the clocks are not only prepared but also enabled, as this is needed for some hardware initialization but, after that, we are disabling but not unpreparing them, leaving an expected state for the aforementioned clock handling strategy. Signed-off-by: AngeloGioacchino Del Regno Tested-by: Nícolas F. R. A. Prado Reviewed-by: Qii Wang --- v2: Fixed typos in commit description drivers/i2c/busses/i2c-mt65xx.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c index f651d3e124d6..bdecb78bfc26 100644 --- a/drivers/i2c/busses/i2c-mt65xx.c +++ b/drivers/i2c/busses/i2c-mt65xx.c @@ -1177,7 +1177,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap, int left_num = num; struct mtk_i2c *i2c = i2c_get_adapdata(adap); - ret = clk_bulk_prepare_enable(I2C_MT65XX_CLK_MAX, i2c->clocks); + ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks); if (ret) return ret; @@ -1231,7 +1231,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap, ret = num; err_exit: - clk_bulk_disable_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks); + clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks); return ret; } @@ -1412,7 +1412,7 @@ static int mtk_i2c_probe(struct platform_device *pdev) return ret; } mtk_i2c_init_hw(i2c); - clk_bulk_disable_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks); + clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks); ret = devm_request_irq(&pdev->dev, irq, mtk_i2c_irq, IRQF_NO_SUSPEND | IRQF_TRIGGER_NONE, @@ -1439,6 +1439,8 @@ static int mtk_i2c_remove(struct platform_device *pdev) i2c_del_adapter(&i2c->adap); + clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks); + return 0; } @@ -1448,6 +1450,7 @@ static int mtk_i2c_suspend_noirq(struct device *dev) struct mtk_i2c *i2c = dev_get_drvdata(dev); i2c_mark_adapter_suspended(&i2c->adap); + clk_bulk_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks); return 0; } @@ -1465,7 +1468,7 @@ static int mtk_i2c_resume_noirq(struct device *dev) mtk_i2c_init_hw(i2c); - clk_bulk_disable_unprepare(I2C_MT65XX_CLK_MAX, i2c->clocks); + clk_bulk_disable(I2C_MT65XX_CLK_MAX, i2c->clocks); i2c_mark_adapter_resumed(&i2c->adap);