[PATCH 1/6] clk: axi-clkgen: Add support for fractional dividers

From: Alexandru Ardelean
Date: Tue Aug 04 2020 - 07:15:05 EST

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
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