linux-kernel - Re: [PATCH 1/1] imx25: Fix LCD pixelclock configuration

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Message-ID: <20160128063213.GJ9070@tiger>
Date:	Thu, 28 Jan 2016 14:32:13 +0800
From:	Shawn Guo <shawnguo@...nel.org>
To:	Carlos Soto <csotoalonso@...il.com>
Cc:	Sascha Hauer <kernel@...gutronix.de>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] imx25: Fix LCD pixelclock configuration

On Wed, Dec 23, 2015 at 09:30:10PM +0100, Carlos Soto wrote:
> Set LCDC base clock (per_7) parent clock to UPLL clock.
> This is needed to allow finer resolution in pixelclock
> 
> Signed-off-by: Carlos Soto <csotoalonso@...il.com>
> ---
>  drivers/clk/imx/clk-imx25.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/clk/imx/clk-imx25.c b/drivers/clk/imx/clk-imx25.c
> index c4c141c..656340e 100644
> --- a/drivers/clk/imx/clk-imx25.c
> +++ b/drivers/clk/imx/clk-imx25.c
> @@ -238,6 +238,12 @@ static int __init __mx25_clocks_init(unsigned long osc_rate,
>  	clk_set_parent(clk[per5_sel], clk[ahb]);
>  
>  	/*
> +	 * set LCDC base clock (per 7) to highest possible frequency (UPLL)
> +	 * to get best resolution for pixel clock
> +	 */
> +	clk_set_parent(clk[per7_sel], clk[upll]);

This can be done in device tree via assigned-clock-parents without the
need of touching kernel.

Shawn

> +
> +	/*
>  	 * Let's initially set up CLKO parent as ipg, since this configuration
>  	 * is used on some imx25 board designs to clock the audio codec.
>  	 */
> -- 
> 1.7.10.4
> 
>