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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4F659C77B7A for ; Tue, 6 Jun 2023 11:40:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3LDj6Sgmo4kiPJRLYEGouY8RDqWkPS1eUXmnHBqdI78=; b=GZ8FY5/KdVHOwS v0QrP4DskFLvSKyBo+rjiV32f0l//9kXnIbwf6hlGzv9gLpoZzmsQaxwnif3GURy6+RGO6gfW6Mzy L8vBftpHcaMaE6iiwZecGGN+VGuF88en8BVjFi9/rD1B4JkOADopFKauClmIu/i9LIjxLOkklrfTL a3j3ENBrzltoqcmhF0n1sO5SWfc8I/PghzVo+kTKVL5lAoqz1J+CcDMoMuZloVBNy8V3lotLyOmZ8 Z8R1xrWMRVOe3TLjuV4Z4ellV0nqguJM9JMQBVk2n3zHeSB6Sb7OQBqZmGFZgj7I3+G832yc7JOD5 Qx7LoEsgxIOokfkkTJDg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1q6V2e-001TT9-1Q; Tue, 06 Jun 2023 11:40:00 +0000 Received: from madras.collabora.co.uk ([2a00:1098:0:82:1000:25:2eeb:e5ab]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1q6V2a-001TRl-1g; Tue, 06 Jun 2023 11:39:58 +0000 Received: from [IPV6:2001:b07:2ed:14ed:a962:cd4d:a84:1eab] (unknown [IPv6:2001:b07:2ed:14ed:a962:cd4d:a84:1eab]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: kholk11) by madras.collabora.co.uk (Postfix) with ESMTPSA id 74C236606EB5; Tue, 6 Jun 2023 12:39:50 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1686051591; bh=aTOiB1WUAchQeXSapkz3ePBm+TJmWUkMK13QQnVxEaU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mTj8Bvle/QR4IRP4nYvzPVOvgc3fpv94wAG5kR4dxKXc7sRqp+KORHfzDBy03mzAb sxXyR7txUP0XafUsaHmHVyOZJ0qw+xkVGp9gw5EOqXLYKV7nIJFAHn9bNVq4X1HDhA qoukPuPGRsOTfKWt+NnFa10yQQf5cSVqtSl+SZjkBLnt4NikD7Vgstm+QD7XULNrtI ZAVlxKMuMFckAcnDDqTbsVKPD/QPTZx+VW+AAVB2Ftv+A0Qyesf0hHWGx2egAJiwib Ab/qwAMQ0AjhP4KkhQFIg+MCCIIHJ7ezGJMCk3pcZGjnEjkmW1y1pfaHGe3jnz3y99 lOEbjynplSBhQ== Message-ID: Date: Tue, 6 Jun 2023 13:39:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH] serial: 8250_mtk: Simplify clock sequencing and runtime PM Content-Language: en-US To: Chen-Yu Tsai , Greg Kroah-Hartman , Jiri Slaby , Matthias Brugger Cc: John Ogness , linux-serial@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Tony Lindgren References: <20230606091747.2031168-1-wenst@chromium.org> From: AngeloGioacchino Del Regno In-Reply-To: <20230606091747.2031168-1-wenst@chromium.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230606_043956_869034_A8329623 X-CRM114-Status: GOOD ( 26.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Il 06/06/23 11:17, Chen-Yu Tsai ha scritto: > The 8250_mtk driver's runtime PM support has some issues: > > - The bus clock is enabled (through runtime PM callback) later than a > register write > - runtime PM resume callback directly called in probe, but no > pm_runtime_set_active() call is present > - UART PM function calls the callbacks directly, _and_ calls runtime > PM API > - runtime PM callbacks try to do reference counting, adding yet another > count between runtime PM and clocks > > This fragile setup worked in a way, but broke recently with runtime PM > support added to the serial core. The system would hang when the UART > console was probed and brought up. > > Tony provided some potential fixes [1][2], though they were still a bit > complicated. The 8250_dw driver, which the 8250_mtk driver might have > been based on, has a similar structure but simpler runtime PM usage. > > Simplify clock sequencing and runtime PM support in the 8250_mtk driver. > Specifically, the clock is acquired enabled and assumed to be active, > unless toggled through runtime PM suspend/resume. Reference counting is > removed and left to the runtime PM core. The serial pm function now > only calls the runtime PM API. > > [1] https://lore.kernel.org/linux-serial/20230602092701.GP14287@atomide.com/ > [2] https://lore.kernel.org/linux-serial/20230605061511.GW14287@atomide.com/ > > Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") > Suggested-by: Tony Lindgren > Signed-off-by: Chen-Yu Tsai Reviewed-by: AngeloGioacchino Del Regno > --- > drivers/tty/serial/8250/8250_mtk.c | 50 ++++++------------------------ > 1 file changed, 10 insertions(+), 40 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > index aa8e98164d68..74da5676ce67 100644 > --- a/drivers/tty/serial/8250/8250_mtk.c > +++ b/drivers/tty/serial/8250/8250_mtk.c > @@ -431,12 +431,7 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev) > while > (serial_in(up, MTK_UART_DEBUG0)); > > - if (data->clk_count == 0U) { > - dev_dbg(dev, "%s clock count is 0\n", __func__); > - } else { > - clk_disable_unprepare(data->bus_clk); > - data->clk_count--; > - } > + clk_disable_unprepare(data->bus_clk); > > return 0; > } > @@ -444,19 +439,8 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev) > static int __maybe_unused mtk8250_runtime_resume(struct device *dev) > { > struct mtk8250_data *data = dev_get_drvdata(dev); > - int err; > > - if (data->clk_count > 0U) { > - dev_dbg(dev, "%s clock count is %d\n", __func__, > - data->clk_count); > - } else { > - err = clk_prepare_enable(data->bus_clk); > - if (err) { > - dev_warn(dev, "Can't enable bus clock\n"); > - return err; > - } > - data->clk_count++; > - } > + clk_prepare_enable(data->bus_clk); > > return 0; > } > @@ -465,14 +449,12 @@ static void > mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old) > { > if (!state) > - if (!mtk8250_runtime_resume(port->dev)) > - pm_runtime_get_sync(port->dev); > + pm_runtime_get_sync(port->dev); > > serial8250_do_pm(port, state, old); > > if (state) > - if (!pm_runtime_put_sync_suspend(port->dev)) > - mtk8250_runtime_suspend(port->dev); > + pm_runtime_put_sync_suspend(port->dev); > } > > #ifdef CONFIG_SERIAL_8250_DMA > @@ -504,7 +486,7 @@ static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p, > return 0; > } > > - data->bus_clk = devm_clk_get(&pdev->dev, "bus"); > + data->bus_clk = devm_clk_get_enabled(&pdev->dev, "bus"); > if (IS_ERR(data->bus_clk)) > return PTR_ERR(data->bus_clk); > > @@ -587,25 +569,16 @@ static int mtk8250_probe(struct platform_device *pdev) > > platform_set_drvdata(pdev, data); > > - pm_runtime_enable(&pdev->dev); > - err = mtk8250_runtime_resume(&pdev->dev); > - if (err) > - goto err_pm_disable; > - > data->line = serial8250_register_8250_port(&uart); > - if (data->line < 0) { > - err = data->line; > - goto err_pm_disable; > - } > + if (data->line < 0) > + return data->line; > > data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1); > > - return 0; > - > -err_pm_disable: > - pm_runtime_disable(&pdev->dev); > + pm_runtime_set_active(&pdev->dev); > + pm_runtime_enable(&pdev->dev); > > - return err; > + return 0; > } > > static int mtk8250_remove(struct platform_device *pdev) > @@ -619,9 +592,6 @@ static int mtk8250_remove(struct platform_device *pdev) > pm_runtime_disable(&pdev->dev); > pm_runtime_put_noidle(&pdev->dev); > > - if (!pm_runtime_status_suspended(&pdev->dev)) > - mtk8250_runtime_suspend(&pdev->dev); > - > return 0; > } > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel