linux-kernel - Re: [PATCH v7] clk: add si5351 i2c common clock driver

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Date:	Wed, 10 Apr 2013 19:27:25 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Michal Bachraty <michal.bachraty@...eamunlimited.com>
CC:	Daniel Mack <zonque@...il.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Dom Cobley <popcornmix@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Rabeeh Khoury <rabeeh@...id-run.com>,
	Jean-Francois Moine <moinejf@...e.fr>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Guenter Roeck <linux@...ck-us.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7] clk: add si5351 i2c common clock driver

Hooray Google!

Thanks for removing plain text sending from gmail web-frontend.. *sigh*
Sorry for resending this, but HTML mails get rejected by linux mailing lists.

On 04/10/2013 04:48 PM, Michal Bachraty wrote:
> Hi Sebastian,
> This driver doesn't work for me. In my case, u-boot initializes si-5351 and
> power down unused clocks while booting kernel.  there is need for power up
> clocks as was in previous versions of your driver.
> See patch, whre the problem is fixed:
>
> @@ -992,6 +992,10 @@ static long si5351_clkout_round_rate(struct clk_hw *hw,
> unsigned long rate,
>   		} while (1);
>   	}
>   	rate = *parent_rate>>  rdiv;
> +	
> +	/* powerup clkout */
> +	si5351_set_bits(hwdata->drvdata, SI5351_CLK0_CTRL + hwdata->num,
> +			SI5351_CLK_POWERDOWN, 0);
>
>   	dev_dbg(&hwdata->drvdata->client->dev,
>   		"%s - %s: rdiv = %u, parent_rate = %lu, rate = %lu\n",
>
> With this lines, driver works well.

Hmm, is there any driver using the clock output? Does it clk_prepare_enable() the clock?
I tend not to mess with anything the bootloader or eeprom config left disabled. It works
for me, but here the driver will prepare/enable the clock prior use.

> Also,
>
>>> +==Example==
>>> +
>>> +/* 25MHz reference crystal */
>>> +ref25: ref25M {
>>> +	compatible = "fixed-clock";
>>> +	#clock-cells =<0>;
>>> +	clock-frequency =<25000000>;
>>> +};
>>> +
>>> +i2c-master-node {
>>> +
>>> +	/* Si5351a msop10 i2c clock generator */
>>> +	si5351a: clock-generator@60 {
>>> +		compatible = "silabs,si5351a-msop";
>>> +		reg =<0x60>;
>>> +		#address-cells =<1>;
>>> +		#size-cells =<0>;
>>> +		#clock-cells =<1>;
>>> +
>>> +		/* connect xtal input to 25MHz reference */
>>> +		clocks =<&ref25>;
>>> +
>>> +		/* connect xtal input as source of pll0 and pll1 */
>>> +		silabs,pll-source =<0 0>,<1 0>;
>>> +
>>> +		/*
>>> +		 * overwrite clkout0 configuration with:
>>> +		 * - 8mA output drive strength
>>> +		 * - pll0 as clock source of multisynth0
>>> +		 * - multisynth0 as clock source of output divider
>>> +		 * - multisynth0 can change pll0
>>> +		 * - set initial clock frequency of 74.25MHz
>>> +		 */
>>> +		clkout0 {
>>> +			reg =<0>;
>>> +			silabs,drive-strength =<8>;
>>> +			silabs,multisynth-source =<0>;
>>> +			silabs,clock-source =<0>;
>>> +			silabs,pll-master;
>>> +			clock-frequency =<74250000>;
>>> +		};
>>> +
>>> +		/*
>>> +		 * overwrite clkout1 configuration with:
>>> +		 * - 4mA output drive strength
>>> +		 * - pll1 as clock source of multisynth1
>>> +		 * - multisynth1 as clock source of output divider
>>> +		 * - multisynth1 can change pll1
>>> +		 */
>>> +		clkout1 {
>>> +			reg =<1>;
>>> +			silabs,drive-strength =<4>;
>>> +			silabs,multisynth-source =<1>;
>>> +			silabs,clock-source =<0>;
>>> +			pll-master;
>>> +		};
>>> +
>   Is definition of pll-master in clkout1 correct? should not be silabs,pll-
> master ?

Good catch.

Sebastian
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