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Subject[PATCH v2 2/2] clk: lmk04832: add support for digital delay
Date
From: Liam Beguin <lvb@xiphos.com>

The digital delay allows outputs to be delayed from 8 to 1023 VCO
cycles. The delay step can be as small as half the period of the clock
distribution path. For example, a 3.2-GHz VCO frequency results in
156.25-ps steps. The digital delay value takes effect on the clock
output phase after a SYNC event.

This is required to support JESD204B subclass 1.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
drivers/clk/clk-lmk04832.c | 321 ++++++++++++++++++++++++++++++++++++-
1 file changed, 315 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/clk-lmk04832.c b/drivers/clk/clk-lmk04832.c
index 3be037722155..e0f01aacc8f4 100644
--- a/drivers/clk/clk-lmk04832.c
+++ b/drivers/clk/clk-lmk04832.c
@@ -36,16 +36,24 @@
#define LMK04832_REG_CLKOUT_CTRL0(ch) (0x100 + (ch >> 1) * 8)
#define LMK04832_BIT_DCLK_DIV_LSB GENMASK(7, 0)
#define LMK04832_REG_CLKOUT_CTRL1(ch) (0x101 + (ch >> 1) * 8)
+#define LMK04832_BIT_DCLKX_Y_DDLY_LSB GENMASK(7, 0)
#define LMK04832_REG_CLKOUT_CTRL2(ch) (0x102 + (ch >> 1) * 8)
#define LMK04832_BIT_CLKOUTX_Y_PD BIT(7)
+#define LMK04832_BIT_DCLKX_Y_DDLY_PD BIT(4)
+#define LMK04832_BIT_DCLKX_Y_DDLY_MSB GENMASK(3, 2)
#define LMK04832_BIT_DCLK_DIV_MSB GENMASK(1, 0)
#define LMK04832_REG_CLKOUT_SRC_MUX(ch) (0x103 + (ch % 2) + (ch >> 1) * 8)
#define LMK04832_BIT_CLKOUT_SRC_MUX BIT(5)
#define LMK04832_REG_CLKOUT_CTRL3(ch) (0x103 + (ch >> 1) * 8)
#define LMK04832_BIT_DCLKX_Y_PD BIT(4)
#define LMK04832_BIT_DCLKX_Y_DCC BIT(2)
+#define LMK04832_BIT_DCLKX_Y_HS BIT(0)
#define LMK04832_REG_CLKOUT_CTRL4(ch) (0x104 + (ch >> 1) * 8)
#define LMK04832_BIT_SCLK_PD BIT(4)
+#define LMK04832_BIT_SCLKX_Y_DIS_MODE GENMASK(3, 2)
+#define LMK04832_REG_SCLKX_Y_ADLY(ch) (0x105 + (ch >> 1) * 8)
+#define LMK04832_REG_SCLKX_Y_DDLY(ch) (0x106 + (ch >> 1) * 8)
+#define LMK04832_BIT_SCLKX_Y_DDLY GENMASK(3, 0)
#define LMK04832_REG_CLKOUT_FMT(ch) (0x107 + (ch >> 1) * 8)
#define LMK04832_BIT_CLKOUT_FMT(ch) (ch % 2 ? 0xf0 : 0x0f)
#define LMK04832_VAL_CLKOUT_FMT_POWERDOWN 0x00
@@ -72,11 +80,19 @@
#define LMK04832_VAL_VCO_MUX_VCO1 0x01
#define LMK04832_VAL_VCO_MUX_EXT 0x02
#define LMK04832_REG_SYSREF_OUT 0x139
+#define LMK04832_BIT_SYSREF_REQ_EN BIT(6)
#define LMK04832_BIT_SYSREF_MUX GENMASK(1, 0)
+#define LMK04832_VAL_SYSREF_MUX_NORMAL_SYNC 0x00
+#define LMK04832_VAL_SYSREF_MUX_RECLK 0x01
+#define LMK04832_VAL_SYSREF_MUX_PULSER 0x02
#define LMK04832_VAL_SYSREF_MUX_CONTINUOUS 0x03
#define LMK04832_REG_SYSREF_DIV_MSB 0x13a
#define LMK04832_BIT_SYSREF_DIV_MSB GENMASK(4, 0)
#define LMK04832_REG_SYSREF_DIV_LSB 0x13b
+#define LMK04832_REG_SYSREF_DDLY_MSB 0x13c
+#define LMK04832_BIT_SYSREF_DDLY_MSB GENMASK(4, 0)
+#define LMK04832_REG_SYSREF_DDLY_LSB 0x13d
+#define LMK04832_REG_SYSREF_PULSE_CNT 0x13e
#define LMK04832_REG_FB_CTRL 0x13f
#define LMK04832_BIT_PLL2_RCLK_MUX BIT(7)
#define LMK04832_VAL_PLL2_RCLK_MUX_OSCIN 0x00
@@ -95,7 +111,15 @@
#define LMK04832_BIT_SYSREF_DDLY_PD BIT(1)
#define LMK04832_BIT_SYSREF_PLSR_PD BIT(0)
#define LMK04832_REG_SYNC 0x143
+#define LMK04832_BIT_SYNC_CLR BIT(7)
+#define LMK04832_BIT_SYNC_1SHOT_EN BIT(6)
+#define LMK04832_BIT_SYNC_POL BIT(5)
#define LMK04832_BIT_SYNC_EN BIT(4)
+#define LMK04832_BIT_SYNC_MODE GENMASK(1, 0)
+#define LMK04832_VAL_SYNC_MODE_OFF 0x00
+#define LMK04832_VAL_SYNC_MODE_ON 0x01
+#define LMK04832_VAL_SYNC_MODE_PULSER_PIN 0x02
+#define LMK04832_VAL_SYNC_MODE_PULSER_SPI 0x03
#define LMK04832_REG_SYNC_DIS 0x144

/* 0x146 - 0x14a CLKin Control */
@@ -127,6 +151,7 @@
#define LMK04832_BIT_PLL2_N_0 GENMASK(1, 0)
#define LMK04832_REG_PLL2_N_1 0x167
#define LMK04832_REG_PLL2_N_2 0x168
+#define LMK04832_REG_PLL2_DLD_CNT_MSB 0x16a
#define LMK04832_REG_PLL2_DLD_CNT_LSB 0x16b
#define LMK04832_REG_PLL2_LD 0x16e
#define LMK04832_BIT_PLL2_LD_MUX GENMASK(7, 3)
@@ -203,6 +228,11 @@ struct lmk_clkout {
*
* @dev: reference to a struct device, linked to the spi_device
* @regmap: struct regmap instance use to access the chip
+ * @sync_mode: operational mode for SYNC signal
+ * @sysref_mux: select SYSREF source
+ * @sysref_pulse_cnt: number of SYSREF pulses generated while not in continuous
+ * mode.
+ * @sysref_ddly: SYSREF digital delay value
* @oscin: PLL2 input clock
* @vco: reference to the internal VCO clock
* @sclk: reference to the internal sysref clock (SCLK)
@@ -217,6 +247,11 @@ struct lmk04832 {
struct device *dev;
struct regmap *regmap;

+ unsigned int sync_mode;
+ unsigned int sysref_mux;
+ unsigned int sysref_pulse_cnt;
+ unsigned int sysref_ddly;
+
struct clk *oscin;
struct clk_hw vco;
struct clk_hw sclk;
@@ -613,6 +648,212 @@ static int lmk04832_register_vco(struct lmk04832 *lmk)
return devm_clk_hw_register(lmk->dev, &lmk->vco);
}

+static int lmk04832_clkout_set_ddly(struct lmk04832 *lmk, int id)
+{
+ int dclk_div_adj[] = {0, 0, -2, -2, 0, 3, -1, 0};
+ unsigned int sclkx_y_ddly = 10;
+ unsigned int dclkx_y_ddly;
+ unsigned int dclkx_y_div;
+ unsigned int sysref_ddly;
+ unsigned int dclkx_y_hs;
+ unsigned int lsb, msb;
+ int ret;
+
+ ret = regmap_update_bits(lmk->regmap,
+ LMK04832_REG_CLKOUT_CTRL2(id),
+ LMK04832_BIT_DCLKX_Y_DDLY_PD,
+ FIELD_PREP(LMK04832_BIT_DCLKX_Y_DDLY_PD, 0));
+ if (ret)
+ return ret;
+
+ ret = regmap_read(lmk->regmap, LMK04832_REG_SYSREF_DDLY_LSB, &lsb);
+ if (ret)
+ return ret;
+
+ ret = regmap_read(lmk->regmap, LMK04832_REG_SYSREF_DDLY_MSB, &msb);
+ if (ret)
+ return ret;
+
+ sysref_ddly = FIELD_GET(LMK04832_BIT_SYSREF_DDLY_MSB, msb) << 8 | lsb;
+
+ ret = regmap_read(lmk->regmap, LMK04832_REG_CLKOUT_CTRL0(id), &lsb);
+ if (ret)
+ return ret;
+
+ ret = regmap_read(lmk->regmap, LMK04832_REG_CLKOUT_CTRL2(id), &msb);
+ if (ret)
+ return ret;
+
+ dclkx_y_div = FIELD_GET(LMK04832_BIT_DCLK_DIV_MSB, msb) << 8 | lsb;
+
+ ret = regmap_read(lmk->regmap, LMK04832_REG_CLKOUT_CTRL3(id), &lsb);
+ if (ret)
+ return ret;
+
+ dclkx_y_hs = FIELD_GET(LMK04832_BIT_DCLKX_Y_HS, lsb);
+
+ dclkx_y_ddly = sysref_ddly + 1 -
+ dclk_div_adj[dclkx_y_div < 6 ? dclkx_y_div : 7] -
+ dclkx_y_hs + sclkx_y_ddly;
+
+ if (dclkx_y_ddly < 7 || dclkx_y_ddly > 0x3fff) {
+ dev_err(lmk->dev, "DCLKX_Y_DDLY out of range (%d)\n",
+ dclkx_y_ddly);
+ return -EINVAL;
+ }
+
+ ret = regmap_write(lmk->regmap,
+ LMK04832_REG_SCLKX_Y_DDLY(id),
+ FIELD_GET(LMK04832_BIT_SCLKX_Y_DDLY, sclkx_y_ddly));
+ if (ret)
+ return ret;
+
+ ret = regmap_write(lmk->regmap, LMK04832_REG_CLKOUT_CTRL1(id),
+ FIELD_GET(0x00ff, dclkx_y_ddly));
+ if (ret)
+ return ret;
+
+ dev_dbg(lmk->dev, "clkout%02u: sysref_ddly=%u, dclkx_y_ddly=%u, "
+ "dclk_div_adj=%+d, dclkx_y_hs=%u, sclkx_y_ddly=%u\n",
+ id, sysref_ddly, dclkx_y_ddly,
+ dclk_div_adj[dclkx_y_div < 6 ? dclkx_y_div : 7],
+ dclkx_y_hs, sclkx_y_ddly);
+
+ return regmap_update_bits(lmk->regmap, LMK04832_REG_CLKOUT_CTRL2(id),
+ LMK04832_BIT_DCLKX_Y_DDLY_MSB,
+ FIELD_GET(0x0300, dclkx_y_ddly));
+}
+
+/** lmk04832_sclk_sync - Establish deterministic phase relationship between sclk
+ * and dclk
+ *
+ * @lmk: Reference to the lmk device
+ *
+ * The synchronization sequence:
+ * - in the datasheet https://www.ti.com/lit/ds/symlink/lmk04832.pdf, p.31
+ * (8.3.3.1 How to enable SYSREF)
+ * - Ti forum: https://e2e.ti.com/support/clock-and-timing/f/48/t/970972
+ *
+ * Returns 0 or negative errno.
+ */
+static int lmk04832_sclk_sync_sequence(struct lmk04832 *lmk)
+{
+ int ret;
+ int i;
+
+ /* 1. (optional) mute all sysref_outputs during synchronization */
+ /* 2. Enable and write device clock digital delay to applicable clocks */
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_MAIN_PD,
+ LMK04832_BIT_SYSREF_DDLY_PD,
+ FIELD_PREP(LMK04832_BIT_SYSREF_DDLY_PD, 0));
+ if (ret)
+ return ret;
+
+ for (i = 0; i < lmk->clk_data->num; i += 2) {
+ ret = lmk04832_clkout_set_ddly(lmk, i);
+ if (ret)
+ return ret;
+ }
+
+ /*
+ * 3. Configure SYNC_MODE to SYNC_PIN and SYSREF_MUX to Normal SYNC,
+ * and clear SYSREF_REQ_EN (see 6.)
+ */
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYSREF_OUT,
+ LMK04832_BIT_SYSREF_REQ_EN |
+ LMK04832_BIT_SYSREF_MUX,
+ FIELD_PREP(LMK04832_BIT_SYSREF_REQ_EN, 0) |
+ FIELD_PREP(LMK04832_BIT_SYSREF_MUX,
+ LMK04832_VAL_SYSREF_MUX_NORMAL_SYNC));
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_MODE,
+ FIELD_PREP(LMK04832_BIT_SYNC_MODE,
+ LMK04832_VAL_SYNC_MODE_ON));
+ if (ret)
+ return ret;
+
+ /* 4. Clear SYNXC_DISx or applicable clocks and clear SYNC_DISSYSREF */
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYNC_DIS, 0x00);
+ if (ret)
+ return ret;
+
+ /*
+ * 5. If SCLKX_Y_DDLY != 0, Set SYSREF_CLR=1 for at least 15 clock
+ * distribution path cycles (VCO cycles), then back to 0. In
+ * PLL2-only use case, this will be complete in less than one SPI
+ * transaction. If SYSREF local digital delay is not used, this step
+ * can be skipped.
+ */
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_CLR,
+ FIELD_PREP(LMK04832_BIT_SYNC_CLR, 0x01));
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_CLR,
+ FIELD_PREP(LMK04832_BIT_SYNC_CLR, 0x00));
+ if (ret)
+ return ret;
+
+ /*
+ * 6. Toggle SYNC_POL state between inverted and not inverted.
+ * If you use an external signal on the SYNC pin instead of toggling
+ * SYNC_POL, make sure that SYSREF_REQ_EN=0 so that the SYSREF_MUX
+ * does not shift into continuous SYSREF mode.
+ */
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_POL,
+ FIELD_PREP(LMK04832_BIT_SYNC_POL, 0x01));
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_POL,
+ FIELD_PREP(LMK04832_BIT_SYNC_POL, 0x00));
+ if (ret)
+ return ret;
+
+ /* 7. Set all SYNC_DISx=1, including SYNC_DISSYSREF */
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYNC_DIS, 0xff);
+ if (ret)
+ return ret;
+
+ /* 8. Restore state of SYNC_MODE and SYSREF_MUX to desired values */
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYSREF_OUT,
+ LMK04832_BIT_SYSREF_MUX,
+ FIELD_PREP(LMK04832_BIT_SYSREF_MUX,
+ lmk->sysref_mux));
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
+ LMK04832_BIT_SYNC_MODE,
+ FIELD_PREP(LMK04832_BIT_SYNC_MODE,
+ lmk->sync_mode));
+ if (ret)
+ return ret;
+
+ /*
+ * 9. (optional) if SCLKx_y_DIS_MODE was used to mute SYSREF outputs
+ * during the SYNC event, restore SCLKx_y_DIS_MODE=0 for active state,
+ * or set SYSREF_GBL_PD=0 if SCLKx_y_DIS_MODE is set to a conditional
+ * option.
+ */
+
+ /*
+ * 10. (optional) To reduce power consumption, after the synchronization
+ * event is complete, DCLKx_y_DDLY_PD=1 and SYSREF_DDLY_PD=1 disable the
+ * digital delay counters (which are only used immediately after the
+ * SYNC pulse to delay the output by some number of VCO counts).
+ */
+
+ return ret;
+}
+
static int lmk04832_sclk_is_enabled(struct clk_hw *hw)
{
struct lmk04832 *lmk = container_of(hw, struct lmk04832, sclk);
@@ -700,8 +941,16 @@ static int lmk04832_sclk_set_rate(struct clk_hw *hw, unsigned long rate,
if (ret)
return ret;

- return regmap_write(lmk->regmap, LMK04832_REG_SYSREF_DIV_LSB,
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYSREF_DIV_LSB,
FIELD_GET(0x00ff, sysref_div));
+ if (ret)
+ return ret;
+
+ ret = lmk04832_sclk_sync_sequence(lmk);
+ if (ret)
+ dev_err(lmk->dev, "SYNC sequence failed\n");
+
+ return ret;
}

static const struct clk_ops lmk04832_sclk_ops = {
@@ -730,18 +979,37 @@ static int lmk04832_register_sclk(struct lmk04832 *lmk)
ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYSREF_OUT,
LMK04832_BIT_SYSREF_MUX,
FIELD_PREP(LMK04832_BIT_SYSREF_MUX,
- LMK04832_VAL_SYSREF_MUX_CONTINUOUS));
+ lmk->sysref_mux));
+ if (ret)
+ return ret;
+
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYSREF_DDLY_LSB,
+ FIELD_GET(0x00ff, lmk->sysref_ddly));
+ if (ret)
+ return ret;
+
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYSREF_DDLY_MSB,
+ FIELD_GET(0x1f00, lmk->sysref_ddly));
+ if (ret)
+ return ret;
+
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYSREF_PULSE_CNT,
+ ilog2(lmk->sysref_pulse_cnt));
if (ret)
return ret;

ret = regmap_update_bits(lmk->regmap, LMK04832_REG_MAIN_PD,
+ LMK04832_BIT_SYSREF_DDLY_PD |
LMK04832_BIT_SYSREF_PLSR_PD,
- LMK04832_BIT_SYSREF_PLSR_PD);
+ FIELD_PREP(LMK04832_BIT_SYSREF_DDLY_PD, 0) |
+ FIELD_PREP(LMK04832_BIT_SYSREF_PLSR_PD, 0));
if (ret)
return ret;

- ret = regmap_update_bits(lmk->regmap, LMK04832_REG_SYNC,
- LMK04832_BIT_SYNC_EN, 0xff);
+ ret = regmap_write(lmk->regmap, LMK04832_REG_SYNC,
+ FIELD_PREP(LMK04832_BIT_SYNC_POL, 0) |
+ FIELD_PREP(LMK04832_BIT_SYNC_EN, 1) |
+ FIELD_PREP(LMK04832_BIT_SYNC_MODE, lmk->sync_mode));
if (ret)
return ret;

@@ -861,15 +1129,41 @@ static int lmk04832_dclk_set_rate(struct clk_hw *hw, unsigned long rate,
return ret;
}

+ /*
+ * While using Divide-by-2 or Divide-by-3 for DCLK_X_Y_DIV, SYNC
+ * procedure requires to first program Divide-by-4 and then back to
+ * Divide-by-2 or Divide-by-3 before doing SYNC.
+ */
+ if (dclk_div == 2 || dclk_div == 3) {
+ ret = regmap_update_bits(lmk->regmap,
+ LMK04832_REG_CLKOUT_CTRL2(dclk->id),
+ LMK04832_BIT_DCLK_DIV_MSB, 0x00);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(lmk->regmap,
+ LMK04832_REG_CLKOUT_CTRL0(dclk->id), 0x04);
+ if (ret)
+ return ret;
+ }
+
ret = regmap_write(lmk->regmap, LMK04832_REG_CLKOUT_CTRL0(dclk->id),
FIELD_GET(0x0ff, dclk_div));
if (ret)
return ret;

- return regmap_update_bits(lmk->regmap,
+ ret = regmap_update_bits(lmk->regmap,
LMK04832_REG_CLKOUT_CTRL2(dclk->id),
LMK04832_BIT_DCLK_DIV_MSB,
FIELD_GET(0x300, dclk_div));
+ if (ret)
+ return ret;
+
+ ret = lmk04832_sclk_sync_sequence(lmk);
+ if (ret)
+ dev_err(lmk->dev, "SYNC sequence failed\n");
+
+ return ret;
};

static const struct clk_ops lmk04832_dclk_ops = {
@@ -1152,6 +1446,21 @@ static int lmk04832_probe(struct spi_device *spi)

device_property_read_u32(lmk->dev, "lmk,vco-rate", &lmk->vco_rate);

+ lmk->sysref_ddly = 8;
+ device_property_read_u32(lmk->dev, "lmk,sysref-ddly", &lmk->sysref_ddly);
+
+ lmk->sysref_mux = LMK04832_VAL_SYSREF_MUX_CONTINUOUS;
+ device_property_read_u32(lmk->dev, "lmk,sysref-mux",
+ &lmk->sysref_mux);
+
+ lmk->sync_mode = LMK04832_VAL_SYNC_MODE_OFF;
+ device_property_read_u32(lmk->dev, "lmk,sync-mode",
+ &lmk->sync_mode);
+
+ lmk->sysref_pulse_cnt = 4;
+ device_property_read_u32(lmk->dev, "lmk,sysref-pulse-count",
+ &lmk->sysref_pulse_cnt);
+
for_each_child_of_node(lmk->dev->of_node, child) {
int reg;

--
2.30.1.489.g328c10930387
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