linux-kernel - Re: [RFC PATCH 24/40] soundwire: cadence_master: use BIOS defaults for frame shape

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Date:   Fri, 26 Jul 2019 12:20:50 +0200
From:   Cezary Rojewski <cezary.rojewski@...el.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [RFC PATCH 24/40] soundwire: cadence_master: use BIOS defaults
 for frame shape

On 2019-07-26 01:40, Pierre-Louis Bossart wrote:
> +static u32 cdns_set_default_frame_shape(int n_rows, int n_cols)
> +{
> +	u32 val;
> +	int c;
> +	int r;
> +
> +	r = sdw_find_row_index(n_rows);
> +	c = sdw_find_col_index(n_cols);
> +
> +	val = (r << 3) | c;
> +
> +	return val;
> +}
> +
>   /**
>    * sdw_cdns_init() - Cadence initialization
>    * @cdns: Cadence instance
> @@ -977,7 +990,9 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
>   	cdns_writel(cdns, CDNS_MCP_CLK_CTRL0, val);
>   
>   	/* Set the default frame shape */
> -	cdns_writel(cdns, CDNS_MCP_FRAME_SHAPE_INIT, CDNS_DEFAULT_FRAME_SHAPE);
> +	val = cdns_set_default_frame_shape(prop->default_row,
> +					   prop->default_col);
> +	cdns_writel(cdns, CDNS_MCP_FRAME_SHAPE_INIT, val);
>   
>   	/* Set SSP interval to default value */
>   	cdns_writel(cdns, CDNS_MCP_SSP_CTRL0, CDNS_DEFAULT_SSP_INTERVAL);
> 

Suggestion:
declare "generic" _get_frame_frame(rows, cols) instead and let it do the 
bitwise operations for you. Pretty sure this won't be the only place in 
code where reg value for frame_shape needs to be prepared.

Said function could be as simple as:
return (row << 3) | cols;
+inline flag

i.e. could be even a macro..

Otherwise modify _set_default_frame_shape to simply:
return (r << 3) | c

without involving additional local val variable (I don't really see the 
point for any locals there though).