linux-kernel - Re: [PATCH v3 7/9] media: i2c: ds90ub953: Restructure clkout management

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Date:   Tue, 1 Aug 2023 16:53:19 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Satish Nagireddy <satish.nagireddy@...cruise.com>,
        Matti Vaittinen <mazziesaccount@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/9] media: i2c: ds90ub953: Restructure clkout
 management

On Mon, Jul 31, 2023 at 04:24:41PM +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.
> 
> This simplifies the clkout management.

...

> +#define UB953_DEFAULT_CLKOUT_RATE	25000000UL

HZ_PER_MHZ (from units.h)?

...

> +struct ub953_clkout_data {
> +	u32 hs_div;
> +	u32 m;
> +	u32 n;
> +	unsigned long rate;

You may save 4 bytes on some architectures (which do not allow 4-byte alignment
for 64-bit members) by reshuffling the members.

(besides using u32-fract :-)

> +};

...

> +		dev_dbg(dev, "%s %llu * %u / (8 * %u) = %lu (requested %lu)",
> +			__func__, fc_rate, m, n, clkout_rate, target_rate);

__func__ in dev_dbg() is not needed. It's very rare nowadays to debug a kernel
without Dynamic Debug to be on.

...

> +		dev_dbg(dev, "%s %llu / %u * %u / %u = %lu (requested %lu)",
> +			__func__, fc_rate, hs_div, m, n, clkout_rate,
> +			target_rate);

Ditto.

-- 
With Best Regards,
Andy Shevchenko