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    SubjectRe: [PATCH 4/4] clk: si5351: Reset PLL after rate change
    On Thu, Apr 30, 2015 at 07:45:54PM +0200, Sebastian Hesselbarth wrote:
    > When changing PLL rate significantly, PLLs have to be reset. Add a function
    > to perform and check for successful PLL reset.
    >
    > Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
    > ---
    > Cc: Mike Turquette <mturquette@linaro.org>
    > Cc: Stephen Boyd <sboyd@codeaurora.org>
    > Cc: Jean-Francois Moine <moinejf@free.fr>
    > Cc: Michael Welling <mwelling@ieee.org>
    > Cc: Russell King <rmk+linux@arm.linux.org.uk>
    > Cc: devicetree@vger.kernel.org
    > Cc: linux-clk@vger.kernel.org
    > Cc: linux-arm-kernel@lists.infradead.org
    > Cc: linux-kernel@vger.kernel.org
    > ---
    > drivers/clk/clk-si5351.c | 29 +++++++++++++++++++++++++++++
    > 1 file changed, 29 insertions(+)
    >
    > diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
    > index beeb57bbb04c..9b97c134e3c1 100644
    > --- a/drivers/clk/clk-si5351.c
    > +++ b/drivers/clk/clk-si5351.c
    > @@ -366,6 +366,32 @@ static const struct clk_ops si5351_vxco_ops = {
    > * = (MSNx_P1*MSNx_P3 + MSNx_P2 + 512*MSNx_P3)/(128*MSNx_P3)
    > *
    > */
    > +static int si5351_pll_reset(struct si5351_hw_data *hwdata)
    > +{
    > + unsigned long timeout;
    > + u8 mask = (hwdata->num == 0) ?
    > + SI5351_STATUS_LOL_A : SI5351_STATUS_LOL_B;
    > +
    > + si5351_reg_write(hwdata->drvdata, SI5351_PLL_RESET,
    > + (hwdata->num == 0) ? SI5351_PLL_RESET_A :
    > + SI5351_PLL_RESET_B);
    > + timeout = jiffies + msecs_to_jiffies(100);
    > + do {
    > + if ((si5351_reg_read(hwdata->drvdata, SI5351_DEVICE_STATUS) &
    > + mask) == 0)
    > + break;
    > + if (time_after(jiffies, timeout)) {
    > + dev_err(&hwdata->drvdata->client->dev,
    > + "timeout waiting for pll %d reset\n",
    > + hwdata->num);
    > + return -EBUSY;
    > + };
    > + udelay(250);
    > + } while (true);
    > +
    > + return 0;
    > +}
    > +
    > static int _si5351_pll_reparent(struct si5351_driver_data *drvdata,
    > int num, enum si5351_pll_src parent)
    > {
    > @@ -519,6 +545,9 @@ static int si5351_pll_set_rate(struct clk_hw *hw, unsigned long rate,
    > SI5351_CLK_INTEGER_MODE,
    > (hwdata->params.p2 == 0) ? SI5351_CLK_INTEGER_MODE : 0);
    >
    > + /* reset pll after rate change */
    > + si5351_pll_reset(hwdata);
    > +

    What is the point of having a return code if it is not being used?

    > dev_dbg(&hwdata->drvdata->client->dev,
    > "%s - %s: p1 = %lu, p2 = %lu, p3 = %lu, parent_rate = %lu, rate = %lu\n",
    > __func__, __clk_get_name(hwdata->hw.clk),
    > --
    > 2.1.0
    >


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