Message-ID: <1391008584.11756.59.camel@joe-AO722>
Subject: Re: [PATCH v5 17/23] drm/i2c: tda998x: set the PLL division factor
 in range 0..3
From: Joe Perches <joe@perches.com>
To: Jean-Francois Moine <moinejf@free.fr>
Cc: dri-devel@lists.freedesktop.org, Dave Airlie <airlied@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Rob Clark <robdclark@gmail.com>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Wed, 29 Jan 2014 07:16:24 -0800
In-Reply-To: <d4ba259762605793aee726b5e33dcad6a8bd4777.1390986083.git.moinejf@free.fr>
References: <cover.1390986082.git.moinejf@free.fr>
	 <d4ba259762605793aee726b5e33dcad6a8bd4777.1390986083.git.moinejf@free.fr>
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Sender: linux-kernel-owner@vger.kernel.org

On Sat, 2014-01-25 at 18:14 +0100, Jean-Francois Moine wrote:
> The predivider division factor of the register PLL_SERIAL_2 is in the
> range 0..3, the value 0 being used for a division by 1.

trivia:

> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
[]
> @@ -886,6 +886,11 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
>  	}
>  
>  	div = 148500 / mode->clock;
> +	if (div != 0) {
> +		div--;
> +		if (div > 3)
> +			div = 3;
> +	}

perhaps
	clamp(div, 1, 4)
	div--;


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