linux-kernel - Re: [PATCH v4 5/8] media: i2c: max9286: Configure reverse channel amplitude

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Message-ID: <27d1af63-279c-143d-7154-04a24e9a0d2a@ideasonboard.com>
Date:   Thu, 12 Nov 2020 22:38:17 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        laurent.pinchart+renesas@...asonboard.com,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org
Cc:     linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Hyun Kwon <hyunk@...inx.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: Re: [PATCH v4 5/8] media: i2c: max9286: Configure reverse channel
 amplitude

Hi Jacopo,

On 12/11/2020 16:27, Jacopo Mondi wrote:
> Adjust the initial reverse channel amplitude parsing from
> firmware interface the 'maxim,initial-reverse-channel-mV'
> property.
> 
> This change is required for both rdacm20 and rdacm21 camera
> modules to be correctly probed when used in combination with
> the max9286 deserializer.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

> ---
>  drivers/media/i2c/max9286.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 31e27d0f34f1..11ba047f3793 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -163,6 +163,8 @@ struct max9286_priv {
>  	unsigned int mux_channel;
>  	bool mux_open;
>  
> +	u32 reverse_channel_mV;
> +
>  	struct v4l2_ctrl_handler ctrls;
>  	struct v4l2_ctrl *pixelrate;
>  
> @@ -557,10 +559,14 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
>  	 * All enabled sources have probed and enabled their reverse control
>  	 * channels:
>  	 *
> +	 * - Increase the reverse channel amplitude to compensate for the
> +	 *   remote ends high threshold, if not done already
>  	 * - Verify all configuration links are properly detected
>  	 * - Disable auto-ack as communication on the control channel are now
>  	 *   stable.
>  	 */
> +	if (priv->reverse_channel_mV < 170)
> +		max9286_reverse_channel_setup(priv, 170);
>  	max9286_check_config_link(priv, priv->source_mask);
>  
>  	/*
> @@ -967,7 +973,7 @@ static int max9286_setup(struct max9286_priv *priv)
>  	 * only. This should be disabled after the mux is initialised.
>  	 */
>  	max9286_configure_i2c(priv, true);
> -	max9286_reverse_channel_setup(priv, 170);
> +	max9286_reverse_channel_setup(priv, priv->reverse_channel_mV);
>  
>  	/*
>  	 * Enable GMSL links, mask unused ones and autodetect link
> @@ -1235,6 +1241,18 @@ static int max9286_parse_dt(struct max9286_priv *priv)
>  	}
>  	of_node_put(node);
>  
> +	/*
> +	 * Parse the initial value of the reverse channel amplitude from
> +	 * the firmware interface.
> +	 *
> +	 * Default it to 170mV for backward compatibility with DTB that do not
> +	 * provide the property.
> +	 */
> +	if (of_property_read_u32(dev->of_node,
> +				 "maxim,initial-reverse-channel-mV",
> +				 &priv->reverse_channel_mV))
> +		priv->reverse_channel_mV = 170;
> +
>  	priv->route_mask = priv->source_mask;
>  
>  	return 0;
>