From mboxrd@z Thu Jan  1 00:00:00 1970
From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=)
Date: Mon, 7 Sep 2015 20:52:04 +0200
Subject: [PATCH v3 1/8] clk: imx: add common logic to detect early UART
 usage
In-Reply-To: <1441638573-6701-2-git-send-email-l.stach@pengutronix.de>
References: <1441638573-6701-1-git-send-email-l.stach@pengutronix.de>
 <1441638573-6701-2-git-send-email-l.stach@pengutronix.de>
Message-ID: <20150907185204.GB14598@pengutronix.de>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hello Lucas,

On Mon, Sep 07, 2015 at 05:09:26PM +0200, Lucas Stach wrote:
> Both earlycon and earlyprintk depend on the bootloader setup UART
> clocks being retained. This patch adds the common logic to detect such
> situations and make the information available to the clock drivers, as
> well as adding the facilities to disable those clocks at the end of
> the kernel init.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/clk/imx/clk.c | 38 ++++++++++++++++++++++++++++++++++++++
>  drivers/clk/imx/clk.h |  1 +
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
> index df12b5307175..45a073dab435 100644
> --- a/drivers/clk/imx/clk.c
> +++ b/drivers/clk/imx/clk.c
> @@ -73,3 +73,41 @@ void imx_cscmr1_fixup(u32 *val)
>  	*val ^= CSCMR1_FIXUP;
>  	return;
>  }
> +
> +static int imx_keep_uart_clocks __initdata;
> +static struct clk ** const *imx_uart_clocks __initdata;
> +
> +static int __init imx_keep_uart_clocks_param(char *str)
> +{
> +	imx_keep_uart_clocks = 1;
> +
> +	return 0;
> +}
> +__setup_param("earlycon", imx_keep_uart_earlycon,
> +	      imx_keep_uart_clocks_param, 0);
> +__setup_param("earlyprintk", imx_keep_uart_earlyprintk,
> +	      imx_keep_uart_clocks_param, 0);
> +
> +void __init imx_register_uart_clocks(struct clk ** const clks[])
> +{
> +	if (imx_keep_uart_clocks) {
> +		int i;
> +
> +		imx_uart_clocks = clks;
> +		for (i = 0; imx_uart_clocks[i]; i++)
> +			clk_prepare_enable(*imx_uart_clocks[i]);
> +	}
> +}
> +
> +static int __init imx_clk_disable_uart(void)
> +{
> +	if (imx_keep_uart_clocks) {
> +		int i;
> +
> +		for (i = 0; imx_uart_clocks[i]; i++)
> +			clk_disable_unprepare(*imx_uart_clocks[i]);
> +	}
> +
> +	return 0;
> +}
> +late_initcall_sync(imx_clk_disable_uart);

I bet you didn't test if this works when earlyprintk (or earlycon) is
provided on the command line but imx_register_uart_clocks isn't called
(e.g. because this is a Samsung CPU running a multiarch kernel).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |