linux-kernel - Re: [PATCH v3 3/4] tty/serial: meson_uart: add the core clock handling to the driver

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Date:   Mon, 03 Apr 2017 16:57:58 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Helmut Klein <hgkr.klein@...il.com>, gregkh@...uxfoundation.org,
        carlo@...one.org, khilman@...libre.com
Cc:     linux-serial@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] tty/serial: meson_uart: add the core clock
 handling to the driver

On Fri, 2017-03-31 at 18:54 +0200, Helmut Klein wrote:
> This patch gets the core clock as provided by the DT and enables it.
> The code was taken from Amlogic's serial driver, and was tested on my
> board.
> 
> Signed-off-by: Helmut Klein <hgkr.klein@...il.com>
> ---
>  drivers/tty/serial/meson_uart.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index 60f16795d16b..cb99112288eb 100644
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
> @@ -600,6 +600,7 @@ static int meson_uart_probe(struct platform_device *pdev)
>  	struct resource *res_mem, *res_irq;
>  	struct uart_port *port;
>  	struct clk *clk;
> +	struct clk *core_clk;
>  	int ret = 0;
> 
>  	if (pdev->dev.of_node)
> @@ -625,6 +626,15 @@ static int meson_uart_probe(struct platform_device *pdev)
>  	if (!port)
>  		return -ENOMEM;
> 
> +	core_clk = devm_clk_get(&pdev->dev, "core");
> +	if (!IS_ERR(core_clk)) {
> +		ret = clk_prepare_enable(core_clk);

This needs to be balanced with a clk_disable_unprepare() in remove.

You could try play with devm_add_action_or_reset, maybe like this:

devm_add_action_or_reset(dev,
			(void(*)(void *))clk_disable_unprepare,
			core_clk);

Sorry I did not notice it on the v2.


> +		if (ret) {
> +			dev_err(&pdev->dev, "couldn't enable clkc\n");
> +			return ret;
> +		}
> +	}
> +
>  	clk = clk_get(&pdev->dev, NULL);

I still think you should name this one. Otherwise, what the non AO UART will get
here will depends on the order it was declared in DT.

To answer your question from the v2, yes I think it is ok to add clock-names to
the AO-UART. You are doing it for non AO ones so, why not ?


>  	if (IS_ERR(clk))
>  		return PTR_ERR(clk);
> --
> 2.11.0
>