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SubjectRe: [PATCH v3 1/5] clk: rockchip: Add supprot to limit input rate for fractional divider
Date
Quoting Elaine Zhang (2019-09-26 20:00:40)
> diff --git a/drivers/clk/rockchip/clk-px30.c b/drivers/clk/rockchip/clk-px30.c
> index 3a501896b280..6c2f53dc73b6 100644
> --- a/drivers/clk/rockchip/clk-px30.c
> +++ b/drivers/clk/rockchip/clk-px30.c
> @@ -13,6 +13,7 @@
> #include "clk.h"
>
> #define PX30_GRF_SOC_STATUS0 0x480
> +#define PX30_FRAC_MAX_PRATE 600000000
>
> enum px30_plls {
> apll, dpll, cpll, npll, apll_b_h, apll_b_l,
> @@ -420,7 +421,7 @@ enum px30_pmu_plls {
> COMPOSITE_FRACMUX(0, "dclk_vopb_frac", "dclk_vopb_src", CLK_SET_RATE_PARENT,
> PX30_CLKSEL_CON(6), 0,
> PX30_CLKGATE_CON(2), 3, GFLAGS,
> - &px30_dclk_vopb_fracmux),
> + &px30_dclk_vopb_fracmux, 0),
> GATE(DCLK_VOPB, "dclk_vopb", "dclk_vopb_mux", CLK_SET_RATE_PARENT,
> PX30_CLKGATE_CON(2), 4, GFLAGS),
> COMPOSITE(0, "dclk_vopl_src", mux_npll_cpll_p, 0,
> @@ -429,7 +430,7 @@ enum px30_pmu_plls {
> COMPOSITE_FRACMUX(0, "dclk_vopl_frac", "dclk_vopl_src", CLK_SET_RATE_PARENT,
> PX30_CLKSEL_CON(9), 0,
> PX30_CLKGATE_CON(2), 7, GFLAGS,
> - &px30_dclk_vopl_fracmux),
> + &px30_dclk_vopl_fracmux, 0),
> GATE(DCLK_VOPL, "dclk_vopl", "dclk_vopl_mux", CLK_SET_RATE_PARENT,
> PX30_CLKGATE_CON(2), 8, GFLAGS),
>
> @@ -555,7 +556,7 @@ enum px30_pmu_plls {
> COMPOSITE_FRACMUX(0, "clk_pdm_frac", "clk_pdm_src", CLK_SET_RATE_PARENT,

Can you make a new macro COMPOSITE_FRACMUX_PRATE or something that
passes in another argument so that we don't have to change the users
of this macro when they don't care?

> PX30_CLKSEL_CON(27), 0,
> PX30_CLKGATE_CON(9), 10, GFLAGS,
> - &px30_pdm_fracmux),
> + &px30_pdm_fracmux, PX30_FRAC_MAX_PRATE),
> GATE(SCLK_PDM, "clk_pdm", "clk_pdm_mux", CLK_SET_RATE_PARENT,
> PX30_CLKGATE_CON(9), 11, GFLAGS),
>
> diff --git a/drivers/clk/rockchip/clk-rk3399.c b/drivers/clk/rockchip/clk-rk3399.c
> index ce1d2446f142..bda5d50c5319 100644
> --- a/drivers/clk/rockchip/clk-rk3399.c
> +++ b/drivers/clk/rockchip/clk-rk3399.c
> @@ -13,6 +13,12 @@
> #include <dt-bindings/clock/rk3399-cru.h>
> #include "clk.h"
>
> +#define RK3399_I2S_FRAC_MAX_PRATE 800000000
> +#define RK3399_UART_FRAC_MAX_PRATE 800000000
> +#define RK3399_SPDIF_FRAC_MAX_PRATE 600000000
> +#define RK3399_VOP_FRAC_MAX_PRATE 600000000
> +#define RK3399_WIFI_FRAC_MAX_PRATE 600000000

Is the "max rate" really just the frequency of the parent? If so, why
can't round_rate() on the parent figure out what that value is and only
provide that frequency?

> +
> enum rk3399_plls {
> lpll, bpll, dpll, cpll, gpll, npll, vpll,
> };
> diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c
> index 546e810c3560..fac5a4a3f5c3 100644
> --- a/drivers/clk/rockchip/clk.c
> +++ b/drivers/clk/rockchip/clk.c
> @@ -184,12 +184,26 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
> unsigned long p_rate, p_parent_rate;
> struct clk_hw *p_parent;
> unsigned long scale;
> + u32 div;

Why u32 instead of unsigned long?

>
> p_rate = clk_hw_get_rate(clk_hw_get_parent(hw));
> - if ((rate * 20 > p_rate) && (p_rate % rate != 0)) {
> + if (((rate * 20 > p_rate) && (p_rate % rate != 0)) ||
> + (fd->max_prate && fd->max_prate < p_rate)) {
> p_parent = clk_hw_get_parent(clk_hw_get_parent(hw));
> p_parent_rate = clk_hw_get_rate(p_parent);
> *parent_rate = p_parent_rate;
> + if (fd->max_prate && p_parent_rate > fd->max_prate) {
> + div = DIV_ROUND_UP(p_parent_rate, fd->max_prate);
> + *parent_rate = p_parent_rate / div;
> + }
> +
> + if (*parent_rate < rate * 20) {

20 seems very magical.

> + pr_err("%s parent_rate(%ld) is low than rate(%ld)*20, fractional div is not allowed\n",

s/low/lower/?

> + clk_hw_get_name(hw), *parent_rate, rate);
> + *m = 0;
> + *n = 1;
> + return;
> + }
> }
>
> /*
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 2ae7604783dd..30993c0630a3 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -624,6 +624,7 @@ struct clk_hw *clk_hw_register_fixed_factor(struct device *dev,
> * @mwidth: width of the numerator bit field
> * @nshift: shift to the denominator bit field
> * @nwidth: width of the denominator bit field
> + * @max_parent: the maximum frequency of fractional divider parent clock

This doesn't match the name of the member.

> * @lock: register lock
> *
> * Clock with adjustable fractional divider affecting its output frequency.
> @@ -647,6 +648,7 @@ struct clk_fractional_divider {
> u8 nwidth;
> u32 nmask;
> u8 flags;
> + unsigned long max_prate;


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