linux-kernel - Re: [PATCH v14 17/18] media: i2c: ds90ub953: Restructure clkout management

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Date:   Fri, 16 Jun 2023 17:37:37 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Wolfram Sang <wsa@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Peter Rosin <peda@...ntia.se>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Michael Tretter <m.tretter@...gutronix.de>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mike Pagano <mpagano@...too.org>,
        Krzysztof Hałasa <khalasa@...p.pl>,
        Marek Vasut <marex@...x.de>,
        Satish Nagireddy <satish.nagireddy@...cruise.com>
Subject: Re: [PATCH v14 17/18] media: i2c: ds90ub953: Restructure clkout
 management

On Fri, Jun 16, 2023 at 04:59:21PM +0300, Tomi Valkeinen wrote:
> Separate clkout calculations and register writes into two functions:
> ub953_calc_clkout_params and ub953_write_clkout_regs, and add a struct
> ub953_clkout_data that is used to store the clkout parameters.

...

> +struct ub953_clkout_data {
> +	u32 hs_div;
> +	u32 m;
> +	u32 n;

Please, use struxt u32_fract instead of m/n.

> +	unsigned long rate;
> +};

...

> +static void ub953_calc_clkout_params(struct ub953_data *priv,
> +				     unsigned long target_rate,
> +				     struct ub953_clkout_data *clkout_data)
> +{
> +	struct device *dev = &priv->client->dev;
> +	unsigned long clkout_rate;
> +	u64 fc_rate;
> +
> +	fc_rate = ub953_get_fc_rate(priv);
> +
> +	if (priv->hw_data->is_ub971) {
> +		u8 m, n;

Ditto. struct u8_fract; (But probably needs to be added into math.h.
I'll Ack/Rb such a patch when one appears.

> +		clkout_rate = ub953_calc_clkout_ub971(priv, target_rate,
> +						      fc_rate, &m, &n);

Can be also parameter to that function.

> +		clkout_data->m = m;
> +		clkout_data->n = n;
> +
> +		dev_dbg(dev, "%s %llu * %u / (8 * %u) = %lu (requested %lu)",
> +			__func__, fc_rate, m, n, clkout_rate, target_rate);
> +	} else {
> +		u8 hs_div, m, n;

Yeah, and so on...

> +		clkout_rate = ub953_calc_clkout_ub953(priv, target_rate,
> +						      fc_rate, &hs_div, &m, &n);
> +
> +		clkout_data->hs_div = hs_div;
> +		clkout_data->m = m;
> +		clkout_data->n = n;
> +
> +		dev_dbg(dev, "%s %llu / %u * %u / %u = %lu (requested %lu)",
> +			__func__, fc_rate, hs_div, m, n, clkout_rate,
> +			target_rate);
> +	}
> +
> +	clkout_data->rate = clkout_rate;
> +}

-- 
With Best Regards,
Andy Shevchenko