Re: [PATCH v4 05/11] clk: Introduce clk-tps68470 driver

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Mon, Oct 25, 2021 at 12:42 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> The TPS68470 PMIC provides Clocks, GPIOs and Regulators. At present in
> the kernel the Regulators and Clocks are controlled by an OpRegion
> driver designed to work with power control methods defined in ACPI, but
> some platforms lack those methods, meaning drivers need to be able to
> consume the resources of these chips through the usual frameworks.
>
> This commit adds a driver for the clocks provided by the tps68470,
> and is designed to bind to the platform_device registered by the
> intel_skl_int3472 module.

...

> +/*
> + *  The PLL is used to multiply the crystal oscillator
> + *  frequency range of 3 MHz to 27 MHz by a programmable
> + *  factor of F = (M/N)*(1/P) such that the output
> + *  available at the HCLK_A or HCLK_B pins are in the range
> + *  of 4 MHz to 64 MHz in increments of 0.1 MHz

Missed (grammatical) period.

> + *
> + * hclk_# = osc_in * (((plldiv*2)+320) / (xtaldiv+30)) * (1 / 2^postdiv)
> + *
> + * PLL_REF_CLK should be as close as possible to 100kHz
> + * PLL_REF_CLK = input clk / XTALDIV[7:0] + 30)
> + *
> + * PLL_VCO_CLK = (PLL_REF_CLK * (plldiv*2 + 320))
> + *
> + * BOOST should be as close as possible to 2Mhz
> + * BOOST = PLL_VCO_CLK / (BOOSTDIV[4:0] + 16) *
> + *
> + * BUCK should be as close as possible to 5.2Mhz
> + * BUCK = PLL_VCO_CLK / (BUCKDIV[3:0] + 5)
> + *
> + * osc_in   xtaldiv  plldiv   postdiv   hclk_#
> + * 20Mhz    170      32       1         19.2Mhz
> + * 20Mhz    170      40       1         20Mhz
> + * 20Mhz    170      80       1         24Mhz

> + *

Redundant empty line.

> + */

...

> +       /* disable clock first */

Disable
first...

> +       /* and then tri-state the clock outputs */

...and

...

> +       for (i = 0; i < ARRAY_SIZE(clk_freqs); i++) {
> +               diff = clk_freqs[i].freq - rate;
> +               if (diff == 0)
> +                       return i;

> +               diff = abs(diff);

This needs a comment why higher (lower) frequency is okay.

> +               if (diff < best_diff) {
> +                       best_diff = diff;
> +                       best_idx = i;
> +               }
> +       }

...

> +       if (pdata) {
> +               ret = devm_clk_hw_register_clkdev(&pdev->dev,
> +                                                 &tps68470_clkdata->clkout_hw,
> +                                                 pdata->consumer_con_id,
> +                                                 pdata->consumer_dev_name);

if (ret)
  return ret;

> +       }
> +
> +       return ret;

return 0;

--
With Best Regards,
Andy Shevchenko