linux-kernel - Re: [PATCH] tty: owl-uart: fix call balance of owl

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Message-ID: <20250214171405.kvyyespxtfqxhapc@thinkpad>
Date: Fri, 14 Feb 2025 22:44:05 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Vitalii Mordan <mordan@...ras.ru>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Andreas Färber <afaerber@...e.de>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Uwe Kleine-König <u.kleine-koenig@...libre.com>,
	Amit Singh Tomar <amittomer25@...il.com>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-actions@...ts.infradead.org,
	Fedor Pchelkin <pchelkin@...ras.ru>,
	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	Vadim Mutilin <mutilin@...ras.ru>, lvc-project@...uxtesting.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] tty: owl-uart: fix call balance of owl_port->clk
 handling routines

On Thu, Feb 13, 2025 at 02:24:16PM +0300, Vitalii Mordan wrote:
> If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
> all error paths to ensure proper cleanup. However, if uart_add_one_port()
> returns an error in owl_uart_probe(), the owl_port->clk clock will not be
> disabled.
> 
> Use the devm_clk_get_enabled() helper function to ensure proper call
> balance for owl_port->clk.
> 

Do not use newly introduced APIs to fix old bugs. The bug should be fixed
separately to allow backporting and the conversion should be done on top.

- Mani

> Found by Linux Verification Center (linuxtesting.org) with Klever.
> 
> Fixes: abf42d2f333b ("tty: serial: owl: add "much needed" clk_prepare_enable()")
> Cc: stable@...r.kernel.org
> Signed-off-by: Vitalii Mordan <mordan@...ras.ru>
> ---
>  drivers/tty/serial/owl-uart.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
> index 0542882cfbbe..64446820437c 100644
> --- a/drivers/tty/serial/owl-uart.c
> +++ b/drivers/tty/serial/owl-uart.c
> @@ -680,18 +680,12 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	if (!owl_port)
>  		return -ENOMEM;
>  
> -	owl_port->clk = devm_clk_get(&pdev->dev, NULL);
> +	owl_port->clk = devm_clk_get_enabled(&pdev->dev, NULL);
>  	if (IS_ERR(owl_port->clk)) {
> -		dev_err(&pdev->dev, "could not get clk\n");
> +		dev_err(&pdev->dev, "could not get and enable clk\n");
>  		return PTR_ERR(owl_port->clk);
>  	}
>  
> -	ret = clk_prepare_enable(owl_port->clk);
> -	if (ret) {
> -		dev_err(&pdev->dev, "could not enable clk\n");
> -		return ret;
> -	}
> -
>  	owl_port->port.dev = &pdev->dev;
>  	owl_port->port.line = pdev->id;
>  	owl_port->port.type = PORT_OWL;
> @@ -701,7 +695,6 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	owl_port->port.uartclk = clk_get_rate(owl_port->clk);
>  	if (owl_port->port.uartclk == 0) {
>  		dev_err(&pdev->dev, "clock rate is zero\n");
> -		clk_disable_unprepare(owl_port->clk);
>  		return -EINVAL;
>  	}
>  	owl_port->port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_LOW_LATENCY;
> @@ -725,7 +718,6 @@ static void owl_uart_remove(struct platform_device *pdev)
>  
>  	uart_remove_one_port(&owl_uart_driver, &owl_port->port);
>  	owl_uart_ports[pdev->id] = NULL;
> -	clk_disable_unprepare(owl_port->clk);
>  }
>  
>  static struct platform_driver owl_uart_platform_driver = {
> -- 
> 2.25.1
> 

-- 
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