linux-kernel - Re: [PATCH v2] clk: si570: Add a driver for SI570 oscillators

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Date:	Thu, 19 Sep 2013 11:05:12 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	Soren Brinkmann <soren.brinkmann@...inx.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Hyun Kwon <hyunk@...inx.com>,
	Soren Brinkmann <soren.brinkmann@...inx.com>
Subject: Re: [PATCH v2] clk: si570: Add a driver for SI570 oscillators

Quoting Soren Brinkmann (2013-09-18 15:43:38)
> diff --git a/Documentation/devicetree/bindings/clock/silabs,si570.txt b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> new file mode 100644
> index 0000000..7ab5c8b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/silabs,si570.txt
> @@ -0,0 +1,38 @@
> +Binding for Silicon Labs 570, 571, 598 and 599 programmable
> +I2C clock generators.
> +
> +Reference
> +This binding uses the common clock binding[1]. Details about the devices can be
> +found in the data sheets[2][3].
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +[2] Si570/571 Data Sheet
> +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
> +[3] Si598/599 Data Sheet
> +    http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
> +
> +Required properties:
> + - compatible: Shall be one of "silabs,si570", "silabs,si571",
> +                              "silabs,si598", "silabs,si599"
> + - reg: I2C device address.
> + - #clock-cells: From common clock bindings: Shall be 0.
> + - factory-fout: Factory set default frequency. This frequency is part specific.
> +                The correct frequency for the part used has to be provided in
> +                order to generate the correct output frequencies. For more
> +                details, please refer to the data sheet.
> +
> +Optional properties:
> + - clock-output-names: From common clock bindings. Recommended to be "si570".
> + - clock-frequency: Output frequency to generate. This defines the output
> +                   frequency set during boot. It can be reprogrammed during
> +                   runtime using the common clock framework.
> + - temperature-stability-7ppm: Indicate a device with a temperature stability
> +                              of 7ppm

Some DT binding bike-shedding:

Should this be "temperature-stability-ppm = <7>;" ? Do you think that
this value might change in the future?

> diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
> new file mode 100644
> index 0000000..c20dfce
> --- /dev/null
> +++ b/drivers/clk/clk-si570.c
> @@ -0,0 +1,517 @@
<snip>
> +static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
> +{
> +       switch (reg) {
> +       case 135:
> +               return true;
> +       default:
> +               return false;
> +       }
> +}
> +
> +static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
> +{
> +       switch (reg) {
> +       case 7 ... 18:
> +       case 135:
> +       case 137:
> +               return true;
> +       default:
> +               return false;
> +       }
> +}

Should magic numbers above be symbolic constants?

Regards,
Mike
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