linux-kernel - Re: [PATCH 11/16] media: i2c: max9286: Cache channel amplitude

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Message-ID: <2b62ff38-7c9c-c24f-b7a6-8e3a65d3f669@ideasonboard.com>
Date:   Thu, 18 Feb 2021 15:39:37 +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:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/16] media: i2c: max9286: Cache channel amplitude

On 16/02/2021 17:41, Jacopo Mondi wrote:
> Cache the current channel amplitude in a driver variable
> to skip updating it if the new requested value is the same
> as the currently configured one.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

I like this model better than deciding outside of the call :-)

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


> ---
>  drivers/media/i2c/max9286.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 1f14cd817fbf..4afb5ca06448 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -164,6 +164,7 @@ struct max9286_priv {
>  	bool mux_open;
>  
>  	u32 init_rev_chan_mv;
> +	u32 rev_chan_mv;
>  
>  	struct v4l2_ctrl_handler ctrls;
>  	struct v4l2_ctrl *pixelrate;
> @@ -340,8 +341,15 @@ static void max9286_configure_i2c(struct max9286_priv *priv, bool localack)
>  static void max9286_reverse_channel_setup(struct max9286_priv *priv,
>  					  unsigned int chan_amplitude)
>  {
> +	u8 chan_config;
> +
> +	if (priv->rev_chan_mv == chan_amplitude)
> +		return;
> +
> +	priv->rev_chan_mv = chan_amplitude;
> +
>  	/* Reverse channel transmission time: default to 1. */
> -	u8 chan_config = MAX9286_REV_TRF(1);
> +	chan_config = MAX9286_REV_TRF(1);
>  
>  	/*
>  	 * Reverse channel setup.
> @@ -563,8 +571,7 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
>  	 * - Disable auto-ack as communication on the control channel are now
>  	 *   stable.
>  	 */
> -	if (priv->init_rev_chan_mv < 170)
> -		max9286_reverse_channel_setup(priv, 170);
> +	max9286_reverse_channel_setup(priv, 170);
>  	max9286_check_config_link(priv, priv->source_mask);
>  
>  	/*
>