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SubjectRe: [PATCH 2/2] clk: si5351: Powerdown output when clock rate is 0.
On 05/07/2013 10:14 AM, Marek Belisko wrote:
> When rate is 0 powerdown clock output.
>
> Signed-off-by: Marek Belisko<marek.belisko@streamunlimited.com>
> ---
> drivers/clk/clk-si5351.c | 32 +++++++++++++++++++-------------
> 1 file changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
> index a8fc0f4..e254e76 100644
> --- a/drivers/clk/clk-si5351.c
> +++ b/drivers/clk/clk-si5351.c
> @@ -1042,20 +1042,22 @@ static int si5351_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
> struct si5351_hw_data *hwdata =
> container_of(hw, struct si5351_hw_data, hw);
> unsigned long new_rate, new_err, err;
> - unsigned char rdiv;
> + unsigned char rdiv, pdn = 0;
>
> /* round to closed rdiv */
> rdiv = SI5351_OUTPUT_CLK_DIV_1;
> - new_rate = parent_rate;
> - err = abs(new_rate - rate);
> - do {
> - new_rate>>= 1;
> - new_err = abs(new_rate - rate);
> - if (new_err> err || rdiv == SI5351_OUTPUT_CLK_DIV_128)
> - break;
> - rdiv++;
> - err = new_err;
> - } while (1);
> + if (rate) {
> + new_rate = parent_rate;

Marek,

initalizing pdn to SI5351_CLK_POWERDOWN and skip (with goto) to
powerup/down call on zero rate will save us a level of indention here.

> + err = abs(new_rate - rate);
> + do {
> + new_rate>>= 1;
> + new_err = abs(new_rate - rate);
> + if (new_err> err || rdiv == SI5351_OUTPUT_CLK_DIV_128)
> + break;
> + rdiv++;
> + err = new_err;
> + } while (1);

of course, pdn should be set to 0 here.

> + }
>
> /* write output divider */
> switch (hwdata->num) {
> @@ -1075,9 +1077,13 @@ static int si5351_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
> rdiv<< SI5351_OUTPUT_CLK_DIV_SHIFT);
> }
>
> - /* powerup clkout */
> + /* when rate is 0 powerdown output */
> + if (rate == 0)
> + pdn = SI5351_CLK_POWERDOWN;
> +
> + /* powerup/down clkout */
> si5351_set_bits(hwdata->drvdata, SI5351_CLK0_CTRL + hwdata->num,
> - SI5351_CLK_POWERDOWN, 0);
> + SI5351_CLK_POWERDOWN, pdn);
>
> dev_dbg(&hwdata->drvdata->client->dev,
> "%s - %s: rdiv = %u, parent_rate = %lu, rate = %lu\n",



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