Boris Brezillon writes: > All bcm2835 PLLs should be gated before their rate can be changed. > Setting CLK_SET_RATE_GATE will let the core enforce that, but this is > not enough to make the code work in all situations. Indeed, the > CLK_SET_RATE_GATE flag prevents a user from changing the rate while > the clock is enabled, but this check only guarantees there's no Linux > users. In our case, the clock might have been enabled by the > bootloader/FW, and, because we have CLK_IGNORE_UNUSED set, Linux never > disables the PLL. So we have to make sure the PLL is actually disabled > before changing the rate. > > Fixes: 41691b8862e2 ("clk: bcm2835: Add support for programming the audio domain clocks") > Cc: > Signed-off-by: Boris Brezillon > --- > drivers/clk/bcm/clk-bcm2835.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c > index 6c5d4a8e426c..051ce769c109 100644 > --- a/drivers/clk/bcm/clk-bcm2835.c > +++ b/drivers/clk/bcm/clk-bcm2835.c > @@ -678,6 +678,18 @@ static int bcm2835_pll_set_rate(struct clk_hw *hw, > u32 ana[4]; > int i; > > + /* > + * Normally, the CLK_SET_RATE_GATE flag prevents a user from changing > + * the rate while the clock is enabled, but this check only makes sure > + * there's no Linux users. > + * In our case, the clock might have been enabled by the bootloader/FW, > + * and, since CLK_IGNORE_UNUSED flag is set, Linux never disables it. > + * So we have to make sure the clk is actually disabled before changing > + * the rate. > + */ > + if (bcm2835_pll_is_on(hw)) > + bcm2835_pll_off(hw); > + I'm not sure this improves the situation. If the PLL was on, then presumably there's a divider using it and a CM clock using that, so we'll probably end up driving some glitches on them. Does the common clk framework have a way to disable unused clocks from the leaf clocks up to this root, before the general disable-unused-clocks path happens late in the boot process?