linux-kernel - Re: [PATCH 1/2] clk: imx: enable the earlycon uart clocks by parsing from dt

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Date:   Mon, 4 Jan 2021 08:11:52 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Adam Ford <aford173@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Fugang Duan <fugang.duan@....com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] clk: imx: enable the earlycon uart clocks by parsing
 from dt

Hi Adam,

On Tue, Dec 29, 2020 at 08:51:28AM -0600, Adam Ford wrote:
> Remove the earlycon uart clocks that are hard cord in platforms
> clock driver, instead of parsing the earlycon uart port from dt

"instead parse the earlycon uart..."

Otherwise it's confusing what you mean here.

> and enable these clocks from clock property in dt node.
> 
> Fixes: 9461f7b33d11c ("clk: fix CLK_SET_RATE_GATE with clock rate protection")
> Signed-off-by: Fugang Duan <fugang.duan@....com>
> Signed-off-by: Adam Ford <aford173@...il.com>
> ---
> Based on NXP's code base and adapted for 5.11-rc1.
> https://source.codeaurora.org/external/imx/linux-imx/commit/drivers/clk/imx/clk.c?h=imx_5.4.47_2.2.0&id=754ae82cc55b7445545fc2f092a70e0f490e9c1b
> 
> The original signed-off was retained.
> Added the fixes tag.
> ---
>  drivers/clk/imx/clk.c | 43 +++++++++++++++++++++++++++++--------------
>  1 file changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> index 47882c51cb85..c32b46890945 100644
> --- a/drivers/clk/imx/clk.c
> +++ b/drivers/clk/imx/clk.c
> @@ -148,7 +148,7 @@ void imx_cscmr1_fixup(u32 *val)
>  
>  #ifndef MODULE
>  static int imx_keep_uart_clocks;
> -static struct clk ** const *imx_uart_clocks;
> +static bool imx_uart_clks_on;
>  
>  static int __init imx_keep_uart_clocks_param(char *str)
>  {
> @@ -161,25 +161,40 @@ __setup_param("earlycon", imx_keep_uart_earlycon,
>  __setup_param("earlyprintk", imx_keep_uart_earlyprintk,
>  	      imx_keep_uart_clocks_param, 0);
>  
> -void imx_register_uart_clocks(struct clk ** const clks[])
> +static void imx_earlycon_uart_clks_onoff(bool is_on)

"is_on" sounds like it's the current state of the clock, but actually
the variable is used for the desired state, so I suggest using plain
"on" as name.

>  {
> -	if (imx_keep_uart_clocks) {
> -		int i;
> +	struct clk *uart_clk;
> +	int i = 0;
>  
> -		imx_uart_clocks = clks;
> -		for (i = 0; imx_uart_clocks[i]; i++)
> -			clk_prepare_enable(*imx_uart_clocks[i]);
> -	}
> +	if (!imx_keep_uart_clocks || (!is_on && !imx_uart_clks_on))
> +		return;
> +
> +	/* only support dt */
> +	if (!of_stdout)
> +		return;
> +
> +	do {
> +		uart_clk = of_clk_get(of_stdout, i++);

of_clk_get() allocates memory and gets you a reference to the clock. You
have to release the clock with clk_put(). I think what you have to do
here is to fill an array with clks when called from
imx_register_uart_clocks() and when called from imx_clk_disable_uart()
use that array to clk_disable_unprepare()/clk_put() the clocks.

Sascha

> +		if (IS_ERR(uart_clk))
> +			break;
> +
> +		if (is_on)
> +			clk_prepare_enable(uart_clk);
> +		else
> +			clk_disable_unprepare(uart_clk);
> +	} while (true);
> +
> +	if (is_on)
> +		imx_uart_clks_on = true;
> +}
> +void imx_register_uart_clocks(struct clk ** const clks[])
> +{
> +	imx_earlycon_uart_clks_onoff(true);
>  }
>  
>  static int __init imx_clk_disable_uart(void)
>  {
> -	if (imx_keep_uart_clocks && imx_uart_clocks) {
> -		int i;
> -
> -		for (i = 0; imx_uart_clocks[i]; i++)
> -			clk_disable_unprepare(*imx_uart_clocks[i]);
> -	}
> +	imx_earlycon_uart_clks_onoff(false);
>  
>  	return 0;
>  }
> -- 
> 2.25.1
> 
> 

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