The patch enables spread spectrum clocking (SSC) for MPU and LCD PLLs. As reported by the TI spruh73x/spruhl7x RM, SSC is only supported for the DISP/LCD and MPU PLLs on am33xx/am43xx. SSC is not supported for DDR, PER, and CORE PLLs.
Calculating the required values and setting the registers accordingly was taken from the set_mpu_spreadspectrum routine contained in the arch/arm/mach-omap2/am33xx/clock_am33xx.c file of the u-boot project.
In locked condition, DPLL output clock = CLKINP *[M/N]. In case of SSC enabled, the reference manual explains that there is a restriction of range of M values. Since the clk_ti_am3_dpll_round_rate() attempts to select the minimum possible N, the value of M obtained is not guaranteed to be within the range required. With the new "ti,min-div" parameter it is possible to increase N and consequently M to satisfy the constraint imposed by SSC.
Link: https://lore.kernel.org/r/20210606202253.31649-6-dariobin@libero.it Signed-off-by: Dario Binacchi dariobin@libero.it
---
arch/arm/include/asm/arch-am33xx/clock.h | 12 +++ drivers/clk/ti/clk-am3-dpll.c | 131 ++++++++++++++++++++++- 2 files changed, 140 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/arch-am33xx/clock.h b/arch/arm/include/asm/arch-am33xx/clock.h index 5d775902bb..79e3b8c7d9 100644 --- a/arch/arm/include/asm/arch-am33xx/clock.h +++ b/arch/arm/include/asm/arch-am33xx/clock.h @@ -78,6 +78,18 @@ #define CM_CLKSEL_DPLL_N_SHIFT 0 #define CM_CLKSEL_DPLL_N_MASK 0x7F
+/* CM_SSC_DELTAM_DPLL */ +#define CM_SSC_DELTAM_DPLL_FRAC_SHIFT 0 +#define CM_SSC_DELTAM_DPLL_FRAC_MASK GENMASK(17, 0) +#define CM_SSC_DELTAM_DPLL_INT_SHIFT 18 +#define CM_SSC_DELTAM_DPLL_INT_MASK GENMASK(19, 18) + +/* CM_SSC_MODFREQ_DPLL */ +#define CM_SSC_MODFREQ_DPLL_MANT_SHIFT 0 +#define CM_SSC_MODFREQ_DPLL_MANT_MASK GENMASK(6, 0) +#define CM_SSC_MODFREQ_DPLL_EXP_SHIFT 7 +#define CM_SSC_MODFREQ_DPLL_EXP_MASK GENMASK(10, 8) + struct dpll_params { u32 m; u32 n; diff --git a/drivers/clk/ti/clk-am3-dpll.c b/drivers/clk/ti/clk-am3-dpll.c index 916d308034..398a011a5c 100644 --- a/drivers/clk/ti/clk-am3-dpll.c +++ b/drivers/clk/ti/clk-am3-dpll.c @@ -27,11 +27,17 @@ struct clk_ti_am3_dpll_priv { struct clk_ti_reg clkmode_reg; struct clk_ti_reg idlest_reg; struct clk_ti_reg clksel_reg; + struct clk_ti_reg ssc_deltam_reg; + struct clk_ti_reg ssc_modfreq_reg; struct clk clk_bypass; struct clk clk_ref; u16 last_rounded_mult; u8 last_rounded_div; + u8 min_div; ulong max_rate; + u32 ssc_modfreq; + u32 ssc_deltam; + bool ssc_downspread; };
static ulong clk_ti_am3_dpll_round_rate(struct clk *clk, ulong rate) @@ -51,7 +57,7 @@ static ulong clk_ti_am3_dpll_round_rate(struct clk *clk, ulong rate) err = rate; err_min = rate; ref_rate = clk_get_rate(&priv->clk_ref); - for (d = 1; err_min && d <= 128; d++) { + for (d = priv->min_div; err_min && d <= 128; d++) { for (m = 2; m <= 2047; m++) { r = (ref_rate * m) / d; err = abs(r - rate); @@ -71,8 +77,8 @@ static ulong clk_ti_am3_dpll_round_rate(struct clk *clk, ulong rate)
priv->last_rounded_mult = mult; priv->last_rounded_div = div; - dev_dbg(clk->dev, "rate=%ld, best_rate=%ld, mult=%d, div=%d\n", rate, - ret, mult, div); + dev_dbg(clk->dev, "rate=%ld, min-div: %d, best_rate=%ld, mult=%d, div=%d\n", + rate, priv->min_div, ret, mult, div); return ret; }
@@ -107,6 +113,96 @@ static int clk_ti_am3_dpll_state(struct clk *clk, u8 state) return 0; }
+/** + * clk_ti_am3_dpll_ssc_program - set spread-spectrum clocking registers + * @clk: struct clk * of DPLL to set + * + * Enable the DPLL spread spectrum clocking if frequency modulation and + * frequency spreading have been set, otherwise disable it. + */ +static void clk_ti_am3_dpll_ssc_program(struct clk *clk) +{ + struct clk_ti_am3_dpll_priv *priv = dev_get_priv(clk->dev); + unsigned long ref_rate; + u32 v, ctrl, mod_freq_divider, exponent, mantissa; + u32 deltam_step, deltam_ceil; + + ctrl = clk_ti_readl(&priv->clkmode_reg); + + if (priv->ssc_modfreq && priv->ssc_deltam) { + ctrl |= CM_CLKMODE_DPLL_SSC_EN_MASK; + + if (priv->ssc_downspread) + ctrl |= CM_CLKMODE_DPLL_SSC_DOWNSPREAD_MASK; + else + ctrl &= ~CM_CLKMODE_DPLL_SSC_DOWNSPREAD_MASK; + + ref_rate = clk_get_rate(&priv->clk_ref); + mod_freq_divider = + (ref_rate / priv->last_rounded_div) / (4 * priv->ssc_modfreq); + if (priv->ssc_modfreq > (ref_rate / 70)) + dev_warn(clk->dev, + "clock: SSC modulation frequency of DPLL %s greater than %ld\n", + clk->dev->name, ref_rate / 70); + + exponent = 0; + mantissa = mod_freq_divider; + while ((mantissa > 127) && (exponent < 7)) { + exponent++; + mantissa /= 2; + } + if (mantissa > 127) + mantissa = 127; + + v = clk_ti_readl(&priv->ssc_modfreq_reg); + v &= ~(CM_SSC_MODFREQ_DPLL_MANT_MASK | CM_SSC_MODFREQ_DPLL_EXP_MASK); + v |= mantissa << __ffs(CM_SSC_MODFREQ_DPLL_MANT_MASK); + v |= exponent << __ffs(CM_SSC_MODFREQ_DPLL_EXP_MASK); + clk_ti_writel(v, &priv->ssc_modfreq_reg); + dev_dbg(clk->dev, + "mod_freq_divider: %u, exponent: %u, mantissa: %u, modfreq_reg: 0x%x\n", + mod_freq_divider, exponent, mantissa, v); + + deltam_step = priv->last_rounded_mult * priv->ssc_deltam; + deltam_step /= 10; + if (priv->ssc_downspread) + deltam_step /= 2; + + deltam_step <<= __ffs(CM_SSC_DELTAM_DPLL_INT_MASK); + deltam_step /= 100; + deltam_step /= mod_freq_divider; + if (deltam_step > 0xFFFFF) + deltam_step = 0xFFFFF; + + deltam_ceil = (deltam_step & CM_SSC_DELTAM_DPLL_INT_MASK) >> + __ffs(CM_SSC_DELTAM_DPLL_INT_MASK); + if (deltam_step & CM_SSC_DELTAM_DPLL_FRAC_MASK) + deltam_ceil++; + + if ((priv->ssc_downspread && + ((priv->last_rounded_mult - (2 * deltam_ceil)) < 20 || + priv->last_rounded_mult > 2045)) || + ((priv->last_rounded_mult - deltam_ceil) < 20 || + (priv->last_rounded_mult + deltam_ceil) > 2045)) + dev_warn(clk->dev, + "clock: SSC multiplier of DPLL %s is out of range\n", + clk->dev->name); + + v = clk_ti_readl(&priv->ssc_deltam_reg); + v &= ~(CM_SSC_DELTAM_DPLL_INT_MASK | CM_SSC_DELTAM_DPLL_FRAC_MASK); + v |= deltam_step << __ffs(CM_SSC_DELTAM_DPLL_INT_MASK | + CM_SSC_DELTAM_DPLL_FRAC_MASK); + clk_ti_writel(v, &priv->ssc_deltam_reg); + dev_dbg(clk->dev, + "deltam_step: %u, deltam_ceil: %u, deltam_reg: 0x%x\n", + deltam_step, deltam_ceil, v); + } else { + ctrl &= ~CM_CLKMODE_DPLL_SSC_EN_MASK; + } + + clk_ti_writel(ctrl, &priv->clkmode_reg); +} + static ulong clk_ti_am3_dpll_set_rate(struct clk *clk, ulong rate) { struct clk_ti_am3_dpll_priv *priv = dev_get_priv(clk->dev); @@ -136,6 +232,8 @@ static ulong clk_ti_am3_dpll_set_rate(struct clk *clk, ulong rate)
clk_ti_writel(v, &priv->clksel_reg);
+ clk_ti_am3_dpll_ssc_program(clk); + /* lock dpll */ clk_ti_am3_dpll_clken(priv, DPLL_EN_LOCK);
@@ -229,6 +327,7 @@ static int clk_ti_am3_dpll_of_to_plat(struct udevice *dev) struct clk_ti_am3_dpll_priv *priv = dev_get_priv(dev); struct clk_ti_am3_dpll_drv_data *data = (struct clk_ti_am3_dpll_drv_data *)dev_get_driver_data(dev); + u32 min_div; int err;
priv->max_rate = data->max_rate; @@ -251,6 +350,32 @@ static int clk_ti_am3_dpll_of_to_plat(struct udevice *dev) return err; }
+ err = clk_ti_get_reg_addr(dev, 3, &priv->ssc_deltam_reg); + if (err) { + dev_err(dev, "failed to get SSC deltam register\n"); + return err; + } + + err = clk_ti_get_reg_addr(dev, 4, &priv->ssc_modfreq_reg); + if (err) { + dev_err(dev, "failed to get SSC modfreq register\n"); + return err; + } + + if (dev_read_u32(dev, "ti,ssc-modfreq-hz", &priv->ssc_modfreq)) + priv->ssc_modfreq = 0; + + if (dev_read_u32(dev, "ti,ssc-deltam", &priv->ssc_deltam)) + priv->ssc_deltam = 0; + + priv->ssc_downspread = dev_read_bool(dev, "ti,ssc-downspread"); + + if (dev_read_u32(dev, "ti,min-div", &min_div) || min_div == 0 || + min_div > 128) + priv->min_div = 1; + else + priv->min_div = min_div; + return 0; }