[PATCH 3/3] clk: ti: add am33xx/am43xx spread spectrum clock support
Dario Binacchi
dariobin at libero.it
Sun Sep 26 11:58:58 CEST 2021
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 at 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;
}
--
2.17.1
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