[PATCH 1/2] clk: axi-clkgen: Add support for fractional dividers

[PATCH 1/2] clk: axi-clkgen: Add support for fractional dividers

[Alexandru Ardelean]

From: Lars-Peter Clausen <lars@metafoo.de>

The axi-clkgen has (optional) fractional dividers on the output clock
divider and feedback clock divider path. Utilizing the fractional dividers
allows for a better resolution of the output clock, being able to
synthesize more frequencies.

Rework the driver support to support the fractional register fields, both
for setting a new rate as well as reading back the current rate from the
hardware.

For setting the rate if no perfect divider settings were found in
non-fractional mode try again in fractional mode and see if better settings
can be found. This appears to be the recommended mode of operation.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---

Series split away from [1]:
  https://lore.kernel.org/linux-clk/20200929144417.89816-9-alexandru.ardelean@analog.com/T/#t

After a review on that, it was concluded that dt-binding conversion to
yaml format would be a good idea.
The conversion went out via:
  https://lore.kernel.org/linux-clk/20201001085035.82938-1-alexandru.ardelean@analog.com/T/#u

It will be reviewed by Rob Herring when he can get to it.
The first 2 patches from the series [1] are independent from dt-binding
context.

 drivers/clk/clk-axi-clkgen.c | 180 +++++++++++++++++++++++++----------
 1 file changed, 129 insertions(+), 51 deletions(-)

diff --git a/drivers/clk/clk-axi-clkgen.c b/drivers/clk/clk-axi-clkgen.c
index 96f351785b41..1df03cc6d089 100644
--- a/drivers/clk/clk-axi-clkgen.c
+++ b/drivers/clk/clk-axi-clkgen.c
@@ -27,8 +27,10 @@
 
 #define AXI_CLKGEN_V2_DRP_STATUS_BUSY	BIT(16)
 
+#define MMCM_REG_CLKOUT5_2	0x07
 #define MMCM_REG_CLKOUT0_1	0x08
 #define MMCM_REG_CLKOUT0_2	0x09
+#define MMCM_REG_CLKOUT6_2	0x13
 #define MMCM_REG_CLK_FB1	0x14
 #define MMCM_REG_CLK_FB2	0x15
 #define MMCM_REG_CLK_DIV	0x16
@@ -40,6 +42,7 @@
 
 #define MMCM_CLKOUT_NOCOUNT	BIT(6)
 
+#define MMCM_CLK_DIV_DIVIDE	BIT(11)
 #define MMCM_CLK_DIV_NOCOUNT	BIT(12)
 
 struct axi_clkgen {
@@ -107,6 +110,8 @@ static void axi_clkgen_calc_params(unsigned long fin, unsigned long fout,
 	unsigned long d, d_min, d_max, _d_min, _d_max;
 	unsigned long m, m_min, m_max;
 	unsigned long f, dout, best_f, fvco;
+	unsigned long fract_shift = 0;
+	unsigned long fvco_min_fract, fvco_max_fract;
 
 	fin /= 1000;
 	fout /= 1000;
@@ -119,42 +124,89 @@ static void axi_clkgen_calc_params(unsigned long fin, unsigned long fout,
 	d_min = max_t(unsigned long, DIV_ROUND_UP(fin, fpfd_max), 1);
 	d_max = min_t(unsigned long, fin / fpfd_min, 80);
 
-	m_min = max_t(unsigned long, DIV_ROUND_UP(fvco_min, fin) * d_min, 1);
-	m_max = min_t(unsigned long, fvco_max * d_max / fin, 64);
+again:
+	fvco_min_fract = fvco_min << fract_shift;
+	fvco_max_fract = fvco_max << fract_shift;
+
+	m_min = max_t(unsigned long, DIV_ROUND_UP(fvco_min_fract, fin) * d_min, 1);
+	m_max = min_t(unsigned long, fvco_max_fract * d_max / fin, 64 << fract_shift);
 
 	for (m = m_min; m <= m_max; m++) {
-		_d_min = max(d_min, DIV_ROUND_UP(fin * m, fvco_max));
-		_d_max = min(d_max, fin * m / fvco_min);
+		_d_min = max(d_min, DIV_ROUND_UP(fin * m, fvco_max_fract));
+		_d_max = min(d_max, fin * m / fvco_min_fract);
 
 		for (d = _d_min; d <= _d_max; d++) {
 			fvco = fin * m / d;
 
 			dout = DIV_ROUND_CLOSEST(fvco, fout);
-			dout = clamp_t(unsigned long, dout, 1, 128);
+			dout = clamp_t(unsigned long, dout, 1, 128 << fract_shift);
 			f = fvco / dout;
 			if (abs(f - fout) < abs(best_f - fout)) {
 				best_f = f;
 				*best_d = d;
-				*best_m = m;
-				*best_dout = dout;
+				*best_m = m << (3 - fract_shift);
+				*best_dout = dout << (3 - fract_shift);
 				if (best_f == fout)
 					return;
 			}
 		}
 	}
+
+	/* Lets see if we find a better setting in fractional mode */
+	if (fract_shift == 0) {
+		fract_shift = 3;
+		goto again;
+	}
 }
 
-static void axi_clkgen_calc_clk_params(unsigned int divider, unsigned int *low,
-	unsigned int *high, unsigned int *edge, unsigned int *nocount)
+struct axi_clkgen_div_params {
+	unsigned int low;
+	unsigned int high;
+	unsigned int edge;
+	unsigned int nocount;
+	unsigned int frac_en;
+	unsigned int frac;
+	unsigned int frac_wf_f;
+	unsigned int frac_wf_r;
+	unsigned int frac_phase;
+};
+
+static void axi_clkgen_calc_clk_params(unsigned int divider,
+	unsigned int frac_divider, struct axi_clkgen_div_params *params)
 {
-	if (divider == 1)
-		*nocount = 1;
-	else
-		*nocount = 0;
 
-	*high = divider / 2;
-	*edge = divider % 2;
-	*low = divider - *high;
+	memset(params, 0x0, sizeof(*params));
+
+	if (divider == 1) {
+		params->nocount = 1;
+		return;
+	}
+
+	if (frac_divider == 0) {
+		params->high = divider / 2;
+		params->edge = divider % 2;
+		params->low = divider - params->high;
+	} else {
+		params->frac_en = 1;
+		params->frac = frac_divider;
+
+		params->high = divider / 2;
+		params->edge = divider % 2;
+		params->low = params->high;
+
+		if (params->edge == 0) {
+			params->high--;
+			params->frac_wf_r = 1;
+		}
+
+		if (params->edge == 0 || frac_divider == 1)
+			params->low--;
+		if (((params->edge == 0) ^ (frac_divider == 1)) ||
+			(divider == 2 && frac_divider == 1))
+			params->frac_wf_f = 1;
+
+		params->frac_phase = params->edge * 4 + frac_divider / 2;
+	}
 }
 
 static void axi_clkgen_write(struct axi_clkgen *axi_clkgen,
@@ -246,15 +298,28 @@ static struct axi_clkgen *clk_hw_to_axi_clkgen(struct clk_hw *clk_hw)
 	return container_of(clk_hw, struct axi_clkgen, clk_hw);
 }
 
+static void axi_clkgen_set_div(struct axi_clkgen *axi_clkgen,
+	unsigned int reg1, unsigned int reg2, unsigned int reg3,
+	struct axi_clkgen_div_params *params)
+{
+	axi_clkgen_mmcm_write(axi_clkgen, reg1,
+		(params->high << 6) | params->low, 0xefff);
+	axi_clkgen_mmcm_write(axi_clkgen, reg2,
+		(params->frac << 12) | (params->frac_en << 11) |
+		(params->frac_wf_r << 10) | (params->edge << 7) |
+		(params->nocount << 6), 0x7fff);
+	if (reg3 != 0) {
+		axi_clkgen_mmcm_write(axi_clkgen, reg3,
+			(params->frac_phase << 11) | (params->frac_wf_f << 10), 0x3c00);
+	}
+}
+
 static int axi_clkgen_set_rate(struct clk_hw *clk_hw,
 	unsigned long rate, unsigned long parent_rate)
 {
 	struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
 	unsigned int d, m, dout;
-	unsigned int nocount;
-	unsigned int high;
-	unsigned int edge;
-	unsigned int low;
+	struct axi_clkgen_div_params params;
 	uint32_t filter;
 	uint32_t lock;
 
@@ -269,21 +334,18 @@ static int axi_clkgen_set_rate(struct clk_hw *clk_hw,
 	filter = axi_clkgen_lookup_filter(m - 1);
 	lock = axi_clkgen_lookup_lock(m - 1);
 
-	axi_clkgen_calc_clk_params(dout, &low, &high, &edge, &nocount);
-	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_CLKOUT0_1,
-		(high << 6) | low, 0xefff);
-	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_CLKOUT0_2,
-		(edge << 7) | (nocount << 6), 0x03ff);
+	axi_clkgen_calc_clk_params(dout >> 3, dout & 0x7, &params);
+	axi_clkgen_set_div(axi_clkgen,  MMCM_REG_CLKOUT0_1, MMCM_REG_CLKOUT0_2,
+		MMCM_REG_CLKOUT5_2, &params);
 
-	axi_clkgen_calc_clk_params(d, &low, &high, &edge, &nocount);
+	axi_clkgen_calc_clk_params(d, 0, &params);
 	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_CLK_DIV,
-		(edge << 13) | (nocount << 12) | (high << 6) | low, 0x3fff);
+		(params.edge << 13) | (params.nocount << 12) |
+		(params.high << 6) | params.low, 0x3fff);
 
-	axi_clkgen_calc_clk_params(m, &low, &high, &edge, &nocount);
-	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_CLK_FB1,
-		(high << 6) | low, 0xefff);
-	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_CLK_FB2,
-		(edge << 7) | (nocount << 6), 0x03ff);
+	axi_clkgen_calc_clk_params(m >> 3, m & 0x7, &params);
+	axi_clkgen_set_div(axi_clkgen,  MMCM_REG_CLK_FB1, MMCM_REG_CLK_FB2,
+		MMCM_REG_CLKOUT6_2, &params);
 
 	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_LOCK1, lock & 0x3ff, 0x3ff);
 	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_LOCK2,
@@ -313,35 +375,51 @@ static long axi_clkgen_round_rate(struct clk_hw *hw, unsigned long rate,
 	return min_t(unsigned long long, tmp, LONG_MAX);
 }
 
+static unsigned int axi_clkgen_get_div(struct axi_clkgen *axi_clkgen,
+	unsigned int reg1, unsigned int reg2)
+{
+	unsigned int val1, val2;
+	unsigned int div;
+
+	axi_clkgen_mmcm_read(axi_clkgen, reg2, &val2);
+	if (val2 & MMCM_CLKOUT_NOCOUNT)
+		return 8;
+
+	axi_clkgen_mmcm_read(axi_clkgen, reg1, &val1);
+
+	div = (val1 & 0x3f) + ((val1 >> 6) & 0x3f);
+	div <<= 3;
+
+	if (val2 & MMCM_CLK_DIV_DIVIDE) {
+		if ((val2 & BIT(7)) && (val2 & 0x7000) != 0x1000)
+			div += 8;
+		else
+			div += 16;
+
+		div += (val2 >> 12) & 0x7;
+	}
+
+	return div;
+}
+
 static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
 	unsigned long parent_rate)
 {
 	struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
 	unsigned int d, m, dout;
-	unsigned int reg;
 	unsigned long long tmp;
+	unsigned int val;
 
-	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLKOUT0_2, &reg);
-	if (reg & MMCM_CLKOUT_NOCOUNT) {
-		dout = 1;
-	} else {
-		axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLKOUT0_1, &reg);
-		dout = (reg & 0x3f) + ((reg >> 6) & 0x3f);
-	}
+	dout = axi_clkgen_get_div(axi_clkgen, MMCM_REG_CLKOUT0_1,
+		MMCM_REG_CLKOUT0_2);
+	m = axi_clkgen_get_div(axi_clkgen, MMCM_REG_CLK_FB1,
+		MMCM_REG_CLK_FB2);
 
-	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_DIV, &reg);
-	if (reg & MMCM_CLK_DIV_NOCOUNT)
+	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_DIV, &val);
+	if (val & MMCM_CLK_DIV_NOCOUNT)
 		d = 1;
 	else
-		d = (reg & 0x3f) + ((reg >> 6) & 0x3f);
-
-	axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_FB2, &reg);
-	if (reg & MMCM_CLKOUT_NOCOUNT) {
-		m = 1;
-	} else {
-		axi_clkgen_mmcm_read(axi_clkgen, MMCM_REG_CLK_FB1, &reg);
-		m = (reg & 0x3f) + ((reg >> 6) & 0x3f);
-	}
+		d = (val & 0x3f) + ((val >> 6) & 0x3f);
 
 	if (d == 0 || dout == 0)
 		return 0;
-- 
2.17.1

[PATCH 2/2] clk: axi-clkgen: Set power bits for fractional mode

[Alexandru Ardelean]

From: Lars-Peter Clausen <lars@metafoo.de>

Using the fractional dividers requires some additional power bits to be
set.

The fractional power bits are not documented and the current heuristic
for setting them seems be insufficient for some cases. Just always set all
the fractional power bits when in fractional mode.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/clk/clk-axi-clkgen.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/clk-axi-clkgen.c b/drivers/clk/clk-axi-clkgen.c
index 1df03cc6d089..14d803e6af62 100644
--- a/drivers/clk/clk-axi-clkgen.c
+++ b/drivers/clk/clk-axi-clkgen.c
@@ -37,6 +37,7 @@
 #define MMCM_REG_LOCK1		0x18
 #define MMCM_REG_LOCK2		0x19
 #define MMCM_REG_LOCK3		0x1a
+#define MMCM_REG_POWER		0x28
 #define MMCM_REG_FILTER1	0x4e
 #define MMCM_REG_FILTER2	0x4f
 
@@ -320,6 +321,7 @@ static int axi_clkgen_set_rate(struct clk_hw *clk_hw,
 	struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
 	unsigned int d, m, dout;
 	struct axi_clkgen_div_params params;
+	uint32_t power = 0;
 	uint32_t filter;
 	uint32_t lock;
 
@@ -331,6 +333,11 @@ static int axi_clkgen_set_rate(struct clk_hw *clk_hw,
 	if (d == 0 || dout == 0 || m == 0)
 		return -EINVAL;
 
+	if ((dout & 0x7) != 0 || (m & 0x7) != 0)
+		power |= 0x9800;
+
+	axi_clkgen_mmcm_write(axi_clkgen, MMCM_REG_POWER, power, 0x9800);
+
 	filter = axi_clkgen_lookup_filter(m - 1);
 	lock = axi_clkgen_lookup_lock(m - 1);
 
-- 
2.17.1

Re: [PATCH 1/2] clk: axi-clkgen: Add support for fractional dividers

[Stephen Boyd]

Quoting Alexandru Ardelean (2020-10-01 01:59:47)
> From: Lars-Peter Clausen <lars@metafoo.de>
> 
> The axi-clkgen has (optional) fractional dividers on the output clock
> divider and feedback clock divider path. Utilizing the fractional dividers
> allows for a better resolution of the output clock, being able to
> synthesize more frequencies.
> 
> Rework the driver support to support the fractional register fields, both
> for setting a new rate as well as reading back the current rate from the
> hardware.
> 
> For setting the rate if no perfect divider settings were found in
> non-fractional mode try again in fractional mode and see if better settings
> can be found. This appears to be the recommended mode of operation.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---

Applied to clk-next

Re: [PATCH 2/2] clk: axi-clkgen: Set power bits for fractional mode

[Stephen Boyd]

Quoting Alexandru Ardelean (2020-10-01 01:59:48)
> From: Lars-Peter Clausen <lars@metafoo.de>
> 
> Using the fractional dividers requires some additional power bits to be
> set.
> 
> The fractional power bits are not documented and the current heuristic
> for setting them seems be insufficient for some cases. Just always set all
> the fractional power bits when in fractional mode.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---

Applied to clk-next