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clk: clocking-wizard: calculate dividers fractional parts
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Calculate dividers fractional parts to optimally modulate output frequency.
Clocking wizard supports having multiplier m and divisors d and o.
Currently the fractional parts of m and o are not utilised.
For the pixel clock usecases a higher accuracy is needed..
Adding support for m and o to have fractional values.

Co-developed-by: Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Signed-off-by: Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Tested-by: Anatoliy Klymenko <anatoliy.klymenko@amd.com>
Link: https://lore.kernel.org/r/20250106082937.29555-1-shubhrajyoti.datta@amd.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
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Shubhrajyoti Datta authored and Stephen Boyd committed Jan 7, 2025
1 parent b00b08a commit 7681f64
Showing 1 changed file with 69 additions and 52 deletions.
121 changes: 69 additions & 52 deletions drivers/clk/xilinx/clk-xlnx-clock-wizard.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,8 @@

#define WZRD_CLKFBOUT_MULT_SHIFT 8
#define WZRD_CLKFBOUT_MULT_MASK (0xff << WZRD_CLKFBOUT_MULT_SHIFT)
#define WZRD_CLKFBOUT_MULT_FRAC_MASK GENMASK(25, 16)
#define WZRD_CLKFBOUT_O_MASK GENMASK(7, 0)
#define WZRD_CLKFBOUT_L_SHIFT 0
#define WZRD_CLKFBOUT_H_SHIFT 8
#define WZRD_CLKFBOUT_L_MASK GENMASK(7, 0)
Expand Down Expand Up @@ -87,14 +89,14 @@
#define DIV_O 0x01
#define DIV_ALL 0x03

#define WZRD_M_MIN 2
#define WZRD_M_MAX 128
#define WZRD_D_MIN 1
#define WZRD_D_MAX 106
#define WZRD_VCO_MIN 800000000
#define WZRD_VCO_MAX 1600000000
#define WZRD_O_MIN 1
#define WZRD_O_MAX 128
#define WZRD_M_MIN 2ULL
#define WZRD_M_MAX 128ULL
#define WZRD_D_MIN 1ULL
#define WZRD_D_MAX 106ULL
#define WZRD_VCO_MIN 800000000ULL
#define WZRD_VCO_MAX 1600000000ULL
#define WZRD_O_MIN 2ULL
#define WZRD_O_MAX 128ULL
#define VER_WZRD_M_MIN 4
#define VER_WZRD_M_MAX 432
#define VER_WZRD_D_MIN 1
Expand Down Expand Up @@ -153,8 +155,10 @@ struct clk_wzrd {
* @flags: clk_wzrd divider flags
* @table: array of value/divider pairs, last entry should have div = 0
* @m: value of the multiplier
* @m_frac: fractional value of the multiplier
* @d: value of the common divider
* @o: value of the leaf divider
* @o_frac: value of the fractional leaf divider
* @lock: register lock
*/
struct clk_wzrd_divider {
Expand All @@ -166,8 +170,10 @@ struct clk_wzrd_divider {
u8 flags;
const struct clk_div_table *table;
u32 m;
u32 m_frac;
u32 d;
u32 o;
u32 o_frac;
spinlock_t *lock; /* divider lock */
};

Expand Down Expand Up @@ -372,38 +378,40 @@ static int clk_wzrd_get_divisors(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
u64 vco_freq, freq, diff, vcomin, vcomax;
u32 m, d, o;
u32 mmin, mmax, dmin, dmax, omin, omax;
u64 vco_freq, freq, diff, vcomin, vcomax, best_diff = -1ULL;
u64 m, d, o;
u64 mmin, mmax, dmin, dmax, omin, omax, mdmin, mdmax;

mmin = WZRD_M_MIN;
mmax = WZRD_M_MAX;
mmin = WZRD_M_MIN << 3;
mmax = WZRD_M_MAX << 3;
dmin = WZRD_D_MIN;
dmax = WZRD_D_MAX;
omin = WZRD_O_MIN;
omax = WZRD_O_MAX;
vcomin = WZRD_VCO_MIN;
vcomax = WZRD_VCO_MAX;
omin = WZRD_O_MIN << 3;
omax = WZRD_O_MAX << 3;
vcomin = WZRD_VCO_MIN << 3;
vcomax = WZRD_VCO_MAX << 3;

for (m = mmin; m <= mmax; m++) {
for (d = dmin; d <= dmax; d++) {
vco_freq = DIV_ROUND_CLOSEST((parent_rate * m), d);
if (vco_freq >= vcomin && vco_freq <= vcomax) {
for (o = omin; o <= omax; o++) {
freq = DIV_ROUND_CLOSEST_ULL(vco_freq, o);
diff = abs(freq - rate);

if (diff < WZRD_MIN_ERR) {
divider->m = m;
divider->d = d;
divider->o = o;
return 0;
}
}
mdmin = max(dmin, div64_u64(parent_rate * m + vcomax / 2, vcomax));
mdmax = min(dmax, div64_u64(parent_rate * m + vcomin / 2, vcomin));
for (d = mdmin; d <= mdmax; d++) {
vco_freq = DIV_ROUND_CLOSEST_ULL((parent_rate * m), d);
o = DIV_ROUND_CLOSEST_ULL(vco_freq, rate);
if (o < omin || o > omax)
continue;
freq = DIV_ROUND_CLOSEST_ULL(vco_freq, o);
diff = freq - rate;
if (diff < best_diff) {
best_diff = diff;
divider->m = m >> 3;
divider->m_frac = (m - (divider->m << 3)) * 125;
divider->d = d;
divider->o = o >> 3;
divider->o_frac = (o - (divider->o << 3)) * 125;
}
}
}
return -EBUSY;
return best_diff < WZRD_MIN_ERR ? 0 : -EBUSY;
}

static int clk_wzrd_reconfig(struct clk_wzrd_divider *divider, void __iomem *div_addr)
Expand Down Expand Up @@ -496,33 +504,22 @@ static int clk_wzrd_dynamic_all_nolock(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
unsigned long vco_freq, rate_div, clockout0_div;
void __iomem *div_addr;
u32 reg, pre, f;
u32 reg;
int err;

err = clk_wzrd_get_divisors(hw, rate, parent_rate);
if (err)
return err;

vco_freq = DIV_ROUND_CLOSEST(parent_rate * divider->m, divider->d);
rate_div = DIV_ROUND_CLOSEST_ULL((vco_freq * WZRD_FRAC_POINTS), rate);

clockout0_div = div_u64(rate_div, WZRD_FRAC_POINTS);

pre = DIV_ROUND_CLOSEST_ULL(vco_freq * WZRD_FRAC_POINTS, rate);
f = (pre - (clockout0_div * WZRD_FRAC_POINTS));
f &= WZRD_CLKOUT_FRAC_MASK;

reg = FIELD_PREP(WZRD_CLKOUT_DIVIDE_MASK, clockout0_div) |
FIELD_PREP(WZRD_CLKOUT0_FRAC_MASK, f);
reg = FIELD_PREP(WZRD_CLKOUT_DIVIDE_MASK, divider->o) |
FIELD_PREP(WZRD_CLKOUT0_FRAC_MASK, divider->o_frac);

writel(reg, divider->base + WZRD_CLK_CFG_REG(0, 2));
/* Set divisor and clear phase offset */
reg = FIELD_PREP(WZRD_CLKFBOUT_MULT_MASK, divider->m) |
FIELD_PREP(WZRD_CLKFBOUT_MULT_FRAC_MASK, divider->m_frac) |
FIELD_PREP(WZRD_DIVCLK_DIVIDE_MASK, divider->d);
writel(reg, divider->base + WZRD_CLK_CFG_REG(0, 0));
writel(divider->o, divider->base + WZRD_CLK_CFG_REG(0, 2));
writel(0, divider->base + WZRD_CLK_CFG_REG(0, 3));
div_addr = divider->base + WZRD_DR_INIT_REG_OFFSET;
return clk_wzrd_reconfig(divider, div_addr);
Expand Down Expand Up @@ -564,18 +561,19 @@ static unsigned long clk_wzrd_recalc_rate_all(struct clk_hw *hw,
unsigned long parent_rate)
{
struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
u32 m, d, o, div, reg, f;
u32 m, d, o, reg, f, mf;
u64 mul;

reg = readl(divider->base + WZRD_CLK_CFG_REG(0, 0));
d = FIELD_GET(WZRD_DIVCLK_DIVIDE_MASK, reg);
m = FIELD_GET(WZRD_CLKFBOUT_MULT_MASK, reg);
mf = FIELD_GET(WZRD_CLKFBOUT_MULT_FRAC_MASK, reg);
reg = readl(divider->base + WZRD_CLK_CFG_REG(0, 2));
o = FIELD_GET(WZRD_DIVCLK_DIVIDE_MASK, reg);
f = FIELD_GET(WZRD_CLKOUT0_FRAC_MASK, reg);

div = DIV_ROUND_CLOSEST(d * (WZRD_FRAC_POINTS * o + f), WZRD_FRAC_POINTS);
return divider_recalc_rate(hw, parent_rate * m, div, divider->table,
divider->flags, divider->width);
mul = m * 1000 + mf;
return DIV_ROUND_CLOSEST_ULL(parent_rate * mul, d * (o * 1000 + f));
}

static unsigned long clk_wzrd_recalc_rate_all_ver(struct clk_hw *hw,
Expand Down Expand Up @@ -646,6 +644,25 @@ static unsigned long clk_wzrd_recalc_rate_all_ver(struct clk_hw *hw,

static long clk_wzrd_round_rate_all(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
u32 m, d, o;
int err;

err = clk_wzrd_get_divisors(hw, rate, *prate);
if (err)
return err;

m = divider->m;
d = divider->d;
o = divider->o;

rate = div_u64(*prate * (m * 1000 + divider->m_frac), d * (o * 1000 + divider->o_frac));
return rate;
}

static long clk_wzrd_ver_round_rate_all(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
unsigned long int_freq;
Expand Down Expand Up @@ -678,7 +695,7 @@ static const struct clk_ops clk_wzrd_ver_divider_ops = {
};

static const struct clk_ops clk_wzrd_ver_div_all_ops = {
.round_rate = clk_wzrd_round_rate_all,
.round_rate = clk_wzrd_ver_round_rate_all,
.set_rate = clk_wzrd_dynamic_all_ver,
.recalc_rate = clk_wzrd_recalc_rate_all_ver,
};
Expand Down

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