linux-kernel - Re: [PATCH] tty: serial: meson: Use devm_clk_get

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Message-ID: <f14d517b-90c9-3741-6f41-6c82a7521f46@baylibre.com>
Date:   Mon, 29 Aug 2022 09:44:28 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH] tty: serial: meson: Use devm_clk_get_enabled() helper

On 24/08/2022 10:06, Christophe JAILLET wrote:
> The devm_clk_get_enabled() helper:
>     - calls devm_clk_get()
>     - calls clk_prepare_enable() and registers what is needed in order to
>       call clk_disable_unprepare() when needed, as a managed resource.
> 
> This simplifies the code, the error handling paths and avoid the need of
> a dedicated function used with devm_add_action_or_reset().
> 
> That said, meson_uart_probe_clock() is now more or less the same as
> devm_clk_get_enabled(), so use this function directly instead.
> 
> This also fixes an (unlikely) unchecked devm_add_action_or_reset() error.
> 
> Based on my test with allyesconfig, this reduces the .o size from:
>     text	   data	    bss	    dec	    hex	filename
>     16350	   5016	    128	  21494	   53f6	drivers/tty/serial/meson_uart.o
> down to:
>     15415	   4784	    128	  20327	   4f67	drivers/tty/serial/meson_uart.o
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> devm_clk_get_enabled() is new and is part of 6.0-rc1
> 
> If the message "couldn't enable clk\n" is of any use, it could be added
> in meson_uart_probe_clocks() with a dev_err_probe() call. It wouldn't be
> exactly the same meaning, but at least something would be logged.
> ---
>   drivers/tty/serial/meson_uart.c | 29 +++--------------------------
>   1 file changed, 3 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index 6c8db19fd572..26de08bf181e 100644
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
> @@ -667,29 +667,6 @@ static struct uart_driver meson_uart_driver = {
>   	.cons		= MESON_SERIAL_CONSOLE,
>   };
>   
> -static inline struct clk *meson_uart_probe_clock(struct device *dev,
> -						 const char *id)
> -{
> -	struct clk *clk = NULL;
> -	int ret;
> -
> -	clk = devm_clk_get(dev, id);
> -	if (IS_ERR(clk))
> -		return clk;
> -
> -	ret = clk_prepare_enable(clk);
> -	if (ret) {
> -		dev_err(dev, "couldn't enable clk\n");
> -		return ERR_PTR(ret);
> -	}
> -
> -	devm_add_action_or_reset(dev,
> -			(void(*)(void *))clk_disable_unprepare,
> -			clk);
> -
> -	return clk;
> -}
> -
>   static int meson_uart_probe_clocks(struct platform_device *pdev,
>   				   struct uart_port *port)
>   {
> @@ -697,15 +674,15 @@ static int meson_uart_probe_clocks(struct platform_device *pdev,
>   	struct clk *clk_pclk = NULL;
>   	struct clk *clk_baud = NULL;
>   
> -	clk_pclk = meson_uart_probe_clock(&pdev->dev, "pclk");
> +	clk_pclk = devm_clk_get_enabled(&pdev->dev, "pclk");
>   	if (IS_ERR(clk_pclk))
>   		return PTR_ERR(clk_pclk);
>   
> -	clk_xtal = meson_uart_probe_clock(&pdev->dev, "xtal");
> +	clk_xtal = devm_clk_get_enabled(&pdev->dev, "xtal");
>   	if (IS_ERR(clk_xtal))
>   		return PTR_ERR(clk_xtal);
>   
> -	clk_baud = meson_uart_probe_clock(&pdev->dev, "baud");
> +	clk_baud = devm_clk_get_enabled(&pdev->dev, "baud");
>   	if (IS_ERR(clk_baud))
>   		return PTR_ERR(clk_baud);
>   

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>