linux-kernel - Re: [PATCH v2 17/28] drm/i2c: tda998x: set the repeat PLL value in range 0..3

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Message-ID: <20140111182602.GF15937@n2100.arm.linux.org.uk>
Date:	Sat, 11 Jan 2014 18:26:02 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Francois Moine <moinejf@...e.fr>
Cc:	dri-devel@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>,
	Dave Airlie <airlied@...il.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 17/28] drm/i2c: tda998x: set the repeat PLL value in
	range 0..3

On Thu, Jan 09, 2014 at 12:05:13PM +0100, Jean-Francois Moine wrote:
> 
> Signed-off-by: Jean-Francois Moine <moinejf@...e.fr>
> ---
>  drivers/gpu/drm/i2c/tda998x_drv.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
> index f60aef9..8a7d8a2 100644
> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
> @@ -220,7 +220,7 @@ struct tda998x_priv {
>  # define PLL_SERIAL_1_SRL_IZ(x)   (((x) & 3) << 1)
>  # define PLL_SERIAL_1_SRL_MAN_IZ  (1 << 6)
>  #define REG_PLL_SERIAL_2          REG(0x02, 0x01)     /* read/write */
> -# define PLL_SERIAL_2_SRL_NOSC(x) (((x) & 3) << 0)
> +# define PLL_SERIAL_2_SRL_NOSC(x) ((x) << 0)
>  # define PLL_SERIAL_2_SRL_PR(x)   (((x) & 0xf) << 4)
>  #define REG_PLL_SERIAL_3          REG(0x02, 0x02)     /* read/write */
>  # define PLL_SERIAL_3_SRL_CCIR    (1 << 0)
> @@ -972,6 +972,11 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
>  	}
>  
>  	div = 148500 / mode->clock;
> +	if (div != 0) {
> +		div--;
> +		if (div > 3)
> +			div = 3;
> +	}

As the driver currently stands, we know that the clock divider works for
the lower resolution modes.  So, as things stand, for 74.25MHz modes,
we get a divisor of one.

Your patch changes this, the divider becomes zero.  I wonder whether
you've tested 720p modes at all with this?

-- 
FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up.  Estimation
in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".
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