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SubjectRe: [PATCH v3 12/25] clk: bcm: rpi: Use CCF boundaries instead of rolling our own
Hi Nicolas,

On Thu, Jun 04, 2020 at 08:02:22PM +0200, Nicolas Saenz Julienne wrote:
> On Wed, 2020-05-27 at 17:45 +0200, Maxime Ripard wrote:
> > The raspberrypi firmware clock driver has a min_rate / max_rate clamping by
> > storing the info it needs in a private structure.
> >
> > However, the CCF already provides such a facility, so we can switch to it
> > to remove the boilerplate.
> >
> > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> > ---
> > drivers/clk/bcm/clk-raspberrypi.c | 18 ++++++++----------
> > 1 file changed, 8 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-
> > raspberrypi.c
> > index a20492fade6a..e135ad28d38d 100644
> > --- a/drivers/clk/bcm/clk-raspberrypi.c
> > +++ b/drivers/clk/bcm/clk-raspberrypi.c
> > @@ -36,9 +36,6 @@ struct raspberrypi_clk {
> > struct rpi_firmware *firmware;
> > struct platform_device *cpufreq;
> >
> > - unsigned long min_rate;
> > - unsigned long max_rate;
> > -
> > struct clk_hw pllb;
> > };
> >
> > @@ -142,13 +139,11 @@ static int raspberrypi_fw_pll_set_rate(struct clk_hw
> > *hw, unsigned long rate,
> > static int raspberrypi_pll_determine_rate(struct clk_hw *hw,
> > struct clk_rate_request *req)
> > {
> > - struct raspberrypi_clk *rpi = container_of(hw, struct raspberrypi_clk,
> > - pllb);
> > u64 div, final_rate;
> > u32 ndiv, fdiv;
> >
> > /* We can't use req->rate directly as it would overflow */
> > - final_rate = clamp(req->rate, rpi->min_rate, rpi->max_rate);
> > + final_rate = clamp(req->rate, req->min_rate, req->max_rate);
> >
> > div = (u64)final_rate << A2W_PLL_FRAC_BITS;
> > do_div(div, req->best_parent_rate);
> > @@ -215,12 +210,15 @@ static int raspberrypi_register_pllb(struct
> > raspberrypi_clk *rpi)
> > dev_info(rpi->dev, "CPU frequency range: min %u, max %u\n",
> > min_rate, max_rate);
> >
> > - rpi->min_rate = min_rate * RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
> > - rpi->max_rate = max_rate * RPI_FIRMWARE_PLLB_ARM_DIV_RATE;
> > -
> > rpi->pllb.init = &init;
> >
> > - return devm_clk_hw_register(rpi->dev, &rpi->pllb);
> > + ret = devm_clk_hw_register(rpi->dev, &rpi->pllb);
> > + if (!ret)
> > + clk_hw_set_rate_range(&rpi->pllb,
> > + min_rate * RPI_FIRMWARE_PLLB_ARM_DIV_RATE,
> > + max_rate *
> > RPI_FIRMWARE_PLLB_ARM_DIV_RATE);
>
> Isn't there a potential race here? Albeit unlikely, cpufreq could show
> up and call clk_round_rate() in between the registration and you
> setting the ranges.

IIRC, driver's probe are not called in parallel but in sequence, so we
should be covered here.

Maxime

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