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Wed, 17 Sep 2025 03:00:59 -0700 (PDT) Message-ID: <939cea9e-d7bd-4a13-b462-17e483f61e4c@gmail.com> Date: Wed, 17 Sep 2025 12:00:57 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] serial: 8250_mtk: Enable baud clock and manage in runtime PM To: Daniel Golle , Greg Kroah-Hartman , Jiri Slaby , AngeloGioacchino Del Regno , Yu Jiaoliang , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= , Andy Shevchenko , Changqi Hu , Sam Shih , Steven Liu , John Crispin , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org References: Content-Language: en-US, ca-ES, es-ES From: Matthias Brugger Autocrypt: addr=matthias.bgg@gmail.com; keydata= xsFNBFP1zgUBEAC21D6hk7//0kOmsUrE3eZ55kjc9DmFPKIz6l4NggqwQjBNRHIMh04BbCMY fL3eT7ZsYV5nur7zctmJ+vbszoOASXUpfq8M+S5hU2w7sBaVk5rpH9yW8CUWz2+ZpQXPJcFa OhLZuSKB1F5JcvLbETRjNzNU7B3TdS2+zkgQQdEyt7Ij2HXGLJ2w+yG2GuR9/iyCJRf10Okq gTh//XESJZ8S6KlOWbLXRE+yfkKDXQx2Jr1XuVvM3zPqH5FMg8reRVFsQ+vI0b+OlyekT/Xe 0Hwvqkev95GG6x7yseJwI+2ydDH6M5O7fPKFW5mzAdDE2g/K9B4e2tYK6/rA7Fq4cqiAw1+u EgO44+eFgv082xtBez5WNkGn18vtw0LW3ESmKh19u6kEGoi0WZwslCNaGFrS4M7OH+aOJeqK fx5dIv2CEbxc6xnHY7dwkcHikTA4QdbdFeUSuj4YhIZ+0QlDVtS1QEXyvZbZky7ur9rHkZvP ZqlUsLJ2nOqsmahMTIQ8Mgx9SLEShWqD4kOF4zNfPJsgEMB49KbS2o9jxbGB+JKupjNddfxZ HlH1KF8QwCMZEYaTNogrVazuEJzx6JdRpR3sFda/0x5qjTadwIW6Cl9tkqe2h391dOGX1eOA 1ntn9O/39KqSrWNGvm+1raHK+Ev1yPtn0Wxn+0oy1tl67TxUjQARAQABzSlNYXR0aGlhcyBC cnVnZ2VyIDxtYXR0aGlhcy5iZ2dAZ21haWwuY29tPsLBkgQTAQIAPAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AWIQTmuZIYwPLDJRwsOhfZFAuyVhMC8QUCWt3scQIZAQAKCRDZFAuy VhMC8WzRD/4onkC+gCxG+dvui5SXCJ7bGLCu0xVtiGC673Kz5Aq3heITsERHBV0BqqctOEBy ZozQQe2Hindu9lasOmwfH8+vfTK+2teCgWesoE3g3XKbrOCB4RSrQmXGC3JYx6rcvMlLV/Ch YMRR3qv04BOchnjkGtvm9aZWH52/6XfChyh7XYndTe5F2bqeTjt+kF/ql+xMc4E6pniqIfkv c0wsH4CkBHqoZl9w5e/b9MspTqsU9NszTEOFhy7p2CYw6JEa/vmzR6YDzGs8AihieIXDOfpT DUr0YUlDrwDSrlm/2MjNIPTmSGHH94ScOqu/XmGW/0q1iar/Yr0leomUOeeEzCqQtunqShtE 4Mn2uEixFL+9jiVtMjujr6mphznwpEqObPCZ3IcWqOFEz77rSL+oqFiEA03A2WBDlMm++Sve 9jpkJBLosJRhAYmQ6ey6MFO6Krylw1LXcq5z1XQQavtFRgZoruHZ3XlhT5wcfLJtAqrtfCe0 aQ0kJW+4zj9/So0uxJDAtGuOpDYnmK26dgFN0tAhVuNInEVhtErtLJHeJzFKJzNyQ4GlCaLw jKcwWcqDJcrx9R7LsCu4l2XpKiyxY6fO4O8DnSleVll9NPfAZFZvf8AIy3EQ8BokUsiuUYHz wUo6pclk55PZRaAsHDX/fNr24uC6Eh5oNQ+v4Pax/gtyyc7BTQRd1TlIARAAm78mTny44Hwd IYNK4ZQH6U5pxcJtU45LLBmSr4DK/7er9chpvJ5pgzCGuI25ceNTEg5FChYcgfNMKqwCAekk V9Iegzi6UK448W1eOp8QeQDS6sHpLSOe8np6/zvmUvhiLokk7tZBhGz+Xs5qQmJPXcag7AMi fuEcf88ZSpChmUB3WflJV2DpxF3sSon5Ew2i53umXLqdRIJEw1Zs2puDJaMqwP3wIyMdrfdI H1ZBBJDIWV/53P52mKtYQ0Khje+/AolpKl96opi6o9VLGeqkpeqrKM2cb1bjo5Zmn4lXl6Nv JRH/ZT68zBtOKUtwhSlOB2bE8IDonQZCOYo2w0opiAgyfpbij8uiI7siBE6bWx2fQpsmi4Jr ZBmhDT6n/uYleGW0DRcZmE2UjeekPWUumN13jaVZuhThV65SnhU05chZT8vU1nATAwirMVeX geZGLwxhscduk3nNb5VSsV95EM/KOtilrH69ZL6Xrnw88f6xaaGPdVyUigBTWc/fcWuw1+nk GJDNqjfSvB7ie114R08Q28aYt8LCJRXYM1WuYloTcIhRSXUohGgHmh7usl469/Ra5CFaMhT3 yCVciuHdZh3u+x+O1sRcOhaFW3BkxKEy+ntxw8J7ZzhgFOgi2HGkOGgM9R03A6ywc0sPwbgk gF7HCLirshP2U/qxWy3C8DkAEQEAAcLBdgQYAQgAIBYhBOa5khjA8sMlHCw6F9kUC7JWEwLx BQJd1TlIAhsMAAoJENkUC7JWEwLxtdcP/jHJ9vI8adFi1HQoWUKCQbZdZ5ZJHayFKIzU9kZE /FHzzzMDZYFgcCTs2kmUVyGloStXpZ0WtdCMMB31jBoQe5x9LtICHEip0irNXm80WsyPCEHU 3wx91QkOmDJftm6T8+F3lqhlc3CwJGpoPY7AVlevzXNJfATZR0+Yh9NhON5Ww4AjsZntqQKx E8rrieLRd+he57ZdRKtRRNGKZOS4wetNhodjfnjhr4Z25BAssD5q+x4uaO8ofGxTjOdrSnRh vhzPCgmP7BKRUZA0wNvFxjboIw8rbTiOFGb1Ebrzuqrrr3WFuK4C1YAF4CyXUBL6Z1Lto//i 44ziQUK9diAgfE/8GhXP0JlMwRUBlXNtErJgItR/XAuFwfO6BOI43P19YwEsuyQq+rubW2Wv rWY2Bj2dXDAKUxS4TuLUf2v/b9Rct36ljzbNxeEWt+Yq4IOY6QHnE+w4xVAkfwjT+Vup8sCp +zFJv9fVUpo/bjePOL4PMP1y+PYrp4PmPmRwoklBpy1ep8m8XURv46fGUHUEIsTwPWs2Q87k 7vjYyrcyAOarX2X5pvMQvpAMADGf2Z3wrCsDdG25w2HztweUNd9QEprtJG8GNNzMOD4cQ82T a7eGvPWPeXauWJDLVR9jHtWT9Ot3BQgmApLxACvwvD1a69jaFKov28SPHxUCQ9Y1Y/Ct In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 16/09/2025 23:37, Daniel Golle wrote: > Some MediaTek SoCs got a gated UART baud clock, which currently gets > disabled as the clk subsystem believes it would be unused. This results in > the uart freezing right after "clk: Disabling unused clocks" on those > platforms. > > Request the baud clock to be prepared and enabled during probe, and to > restore run-time power management capabilities to what it was before commit > e32a83c70cf9 ("serial: 8250-mtk: modify mtk uart power and clock > management") disable and unprepare the baud clock when suspending the UART, > prepare and enable it again when resuming it. > > Fixes: e32a83c70cf9 ("serial: 8250-mtk: modify mtk uart power and clock management") Most of the issues from this commit are already fixed in b6c7ff2693ddc ("serial: 8250_mtk: Simplify clock sequencing and runtime PM") which is more or less a revert of e32a83c70cf9. I think we should add Fixes: b6c7ff2693ddc ("serial: 8250_mtk: Simplify clock sequencing and runtime PM") here as well. It's a fix of a fix :) Regards, Matthias > Reviewed-by: AngeloGioacchino Del Regno > Signed-off-by: Daniel Golle > --- > v3: squash into single patch > v2: add managing run-time PM in dedicated patch > > drivers/tty/serial/8250/8250_mtk.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c > index b44de2ed7413..5875a7b9b4b1 100644 > --- a/drivers/tty/serial/8250/8250_mtk.c > +++ b/drivers/tty/serial/8250/8250_mtk.c > @@ -435,6 +435,7 @@ static int __maybe_unused mtk8250_runtime_suspend(struct device *dev) > while > (serial_in(up, MTK_UART_DEBUG0)); > > + clk_disable_unprepare(data->uart_clk); > clk_disable_unprepare(data->bus_clk); > > return 0; > @@ -445,6 +446,7 @@ static int __maybe_unused mtk8250_runtime_resume(struct device *dev) > struct mtk8250_data *data = dev_get_drvdata(dev); > > clk_prepare_enable(data->bus_clk); > + clk_prepare_enable(data->uart_clk); > > return 0; > } > @@ -475,13 +477,13 @@ static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p, > int dmacnt; > #endif > > - data->uart_clk = devm_clk_get(&pdev->dev, "baud"); > + data->uart_clk = devm_clk_get_enabled(&pdev->dev, "baud"); > if (IS_ERR(data->uart_clk)) { > /* > * For compatibility with older device trees try unnamed > * clk when no baud clk can be found. > */ > - data->uart_clk = devm_clk_get(&pdev->dev, NULL); > + data->uart_clk = devm_clk_get_enabled(&pdev->dev, NULL); > if (IS_ERR(data->uart_clk)) { > dev_warn(&pdev->dev, "Can't get uart clock\n"); > return PTR_ERR(data->uart_clk);