[PATCH v5 6/9] clk: cs2000-cp: add support for dynamic mode

Daniel Mack
2021-09-01T09:36:42Z

The CS2000 chip features two input clocks, REF_CLK and CLK_IN.

In static mode, the output clock (CLK_OUT) is directly derived from
REF_CLK, and CLK_IN is ignored. In dynamic mode, CLK_IN is used by the
digital PLL.

In dynamic mode, a low-frequency ratio configuration that uses a higher
multiplier factor.

Until now, only the static mode and high-frequency divider rations of
the hardware was supported by the driver. This patch adds support for
dynamic mode and both ratios:

* Parse a new OF property 'cirrus,dynamic-mode' to determine the mode
* In dynamic mode, present CLK_IN as parent clock, else use REF_CLK
* The low-frequency ratio mode is automatically selected, depending
on the mode of operation and the given input and output rates

Signed-off-by: Daniel Mack <daniel@zonque.org>
---
drivers/clk/clk-cs2000-cp.c | 111 ++++++++++++++++++++++++------------
1 file changed, 74 insertions(+), 37 deletions(-)

diff --git a/drivers/clk/clk-cs2000-cp.c b/drivers/clk/clk-cs2000-cp.c
index db7290621cef..bd030e156d65 100644
--- a/drivers/clk/clk-cs2000-cp.c
+++ b/drivers/clk/clk-cs2000-cp.c
@@ -49,7 +49,7 @@
#define LOCKCLK_MASK LOCKCLK(0x3)
#define FRACNSRC_MASK (1 << 0)
#define FRACNSRC_STATIC (0 << 0)
-#define FRACNSRC_DYNAMIC (1 << 1)
+#define FRACNSRC_DYNAMIC (1 << 0)

/* GLOBAL_CFG */
#define ENDEV2 (0x1)
@@ -79,6 +79,9 @@ struct cs2000_priv {
struct clk *clk_in;
struct clk *ref_clk;

+ bool dynamic_mode;
+ bool lf_ratio;
+
/* suspend/resume */
unsigned long saved_rate;
unsigned long saved_parent_rate;
@@ -134,17 +137,11 @@ static int cs2000_enable_dev_config(struct cs2000_priv *priv, bool enable)
if (ret < 0)
return ret;

- /* FIXME: for Static ratio mode */
- ret = cs2000_bset(priv, FUNC_CFG2, LFRATIO_MASK,
- LFRATIO_12_20);
- if (ret < 0)
- return ret;
-
return 0;
}

-static int cs2000_clk_in_bound_rate(struct cs2000_priv *priv,
- u32 rate_in)
+static int cs2000_ref_clk_bound_rate(struct cs2000_priv *priv,
+ u32 rate_in)
{
u32 val;

@@ -191,35 +188,37 @@ static int cs2000_clk_out_enable(struct cs2000_priv *priv, bool enable)
(AUXOUTDIS | CLKOUTDIS));
}

-static u32 cs2000_rate_to_ratio(u32 rate_in, u32 rate_out)
+static u32 cs2000_rate_to_ratio(u32 rate_in, u32 rate_out, bool lf_ratio)
{
u64 ratio;
+ u32 multiplier = lf_ratio ? 12 : 20;

/*
- * ratio = rate_out / rate_in * 2^20
+ * ratio = rate_out / rate_in * 2^multiplier
*
* To avoid over flow, rate_out is u64.
* The result should be u32.
*/
- ratio = (u64)rate_out << 20;
+ ratio = (u64)rate_out << multiplier;
do_div(ratio, rate_in);

return ratio;
}

-static unsigned long cs2000_ratio_to_rate(u32 ratio, u32 rate_in)
+static unsigned long cs2000_ratio_to_rate(u32 ratio, u32 rate_in, bool lf_ratio)
{
u64 rate_out;
+ u32 multiplier = lf_ratio ? 12 : 20;

/*
- * ratio = rate_out / rate_in * 2^20
+ * ratio = rate_out / rate_in * 2^multiplier
*
* To avoid over flow, rate_out is u64.
* The result should be u32 or unsigned long.
*/

rate_out = (u64)ratio * rate_in;
- return rate_out >> 20;
+ return rate_out >> multiplier;
}

static int cs2000_ratio_set(struct cs2000_priv *priv,
@@ -232,7 +231,7 @@ static int cs2000_ratio_set(struct cs2000_priv *priv,
if (CH_SIZE_ERR(ch))
return -EINVAL;

- val = cs2000_rate_to_ratio(rate_in, rate_out);
+ val = cs2000_rate_to_ratio(rate_in, rate_out, priv->lf_ratio);
for (i = 0; i < RATIO_REG_SIZE; i++) {
ret = cs2000_write(priv,
Ratio_Add(ch, i),
@@ -265,22 +264,20 @@ static u32 cs2000_ratio_get(struct cs2000_priv *priv, int ch)
static int cs2000_ratio_select(struct cs2000_priv *priv, int ch)
{
int ret;
+ u8 fracnsrc;

if (CH_SIZE_ERR(ch))
return -EINVAL;

- /*
- * FIXME
- *
- * this driver supports static ratio mode only at this point.
- */
ret = cs2000_bset(priv, DEVICE_CFG1, RSEL_MASK, RSEL(ch));
if (ret < 0)
return ret;

+ fracnsrc = priv->dynamic_mode ? FRACNSRC_DYNAMIC : FRACNSRC_STATIC;
+
ret = cs2000_bset(priv, DEVICE_CFG2,
- (AUTORMOD | LOCKCLK_MASK | FRACNSRC_MASK),
- (LOCKCLK(ch) | FRACNSRC_STATIC));
+ AUTORMOD | LOCKCLK_MASK | FRACNSRC_MASK,
+ LOCKCLK(ch) | fracnsrc);
if (ret < 0)
return ret;

@@ -296,17 +293,39 @@ static unsigned long cs2000_recalc_rate(struct clk_hw *hw,

ratio = cs2000_ratio_get(priv, ch);

- return cs2000_ratio_to_rate(ratio, parent_rate);
+ return cs2000_ratio_to_rate(ratio, parent_rate, priv->lf_ratio);
}

static long cs2000_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *parent_rate)
{
+ struct cs2000_priv *priv = hw_to_priv(hw);
u32 ratio;

- ratio = cs2000_rate_to_ratio(*parent_rate, rate);
+ ratio = cs2000_rate_to_ratio(*parent_rate, rate, priv->lf_ratio);
+
+ return cs2000_ratio_to_rate(ratio, *parent_rate, priv->lf_ratio);
+}
+
+static int cs2000_select_ratio_mode(struct cs2000_priv *priv,
+ unsigned long rate,
+ unsigned long parent_rate)
+{
+ /*
+ * From the datasheet:
+ *
+ * | It is recommended that the 12.20 High-Resolution format be
+ * | utilized whenever the desired ratio is less than 4096 since
+ * | the output frequency accuracy of the PLL is directly proportional
+ * | to the accuracy of the timing reference clock and the resolution
+ * | of the R_UD.
+ *
+ * This mode is only available in dynamic mode.
+ */
+ priv->lf_ratio = priv->dynamic_mode && ((rate / parent_rate) > 4096);

- return cs2000_ratio_to_rate(ratio, *parent_rate);
+ return cs2000_bset(priv, FUNC_CFG2, LFRATIO_MASK,
+ priv->lf_ratio ? LFRATIO_20_12 : LFRATIO_12_20);
}

static int __cs2000_set_rate(struct cs2000_priv *priv, int ch,
@@ -315,7 +334,7 @@ static int __cs2000_set_rate(struct cs2000_priv *priv, int ch,
{
int ret;

- ret = cs2000_clk_in_bound_rate(priv, parent_rate);
+ ret = cs2000_select_ratio_mode(priv, rate, parent_rate);
if (ret < 0)
return ret;

@@ -382,8 +401,13 @@ static void cs2000_disable(struct clk_hw *hw)

static u8 cs2000_get_parent(struct clk_hw *hw)
{
- /* always return REF_CLK */
- return REF_CLK;
+ struct cs2000_priv *priv = hw_to_priv(hw);
+
+ /*
+ * In dynamic mode, output rates are derived from CLK_IN.
+ * In static mode, CLK_IN is ignored, so we return REF_CLK instead.
+ */
+ return priv->dynamic_mode ? CLK_IN : REF_CLK;
}

static const struct clk_ops cs2000_ops = {
@@ -424,28 +448,41 @@ static int cs2000_clk_register(struct cs2000_priv *priv)
const char *name = np->name;
static const char *parent_names[CLK_MAX];
u32 aux_out = 0;
+ int ref_clk_rate;
int ch = 0; /* it uses ch0 only at this point */
- int rate;
int ret;

of_property_read_string(np, "clock-output-names", &name);

+ priv->dynamic_mode = of_property_read_bool(np, "cirrus,dynamic-mode");
+ dev_info(dev, "operating in %s mode\n",
+ priv->dynamic_mode ? "dynamic" : "static");
+
of_property_read_u32(np, "cirrus,aux-output-source", &aux_out);
ret = cs2000_bset(priv, DEVICE_CFG1,
AUXOUTSRC_MASK, AUXOUTSRC(aux_out));
if (ret < 0)
return ret;

- /*
- * set default rate as 1/1.
- * otherwise .set_rate which setup ratio
- * is never called if user requests 1/1 rate
- */
- rate = clk_get_rate(priv->ref_clk);
- ret = __cs2000_set_rate(priv, ch, rate, rate);
+ ref_clk_rate = clk_get_rate(priv->ref_clk);
+ ret = cs2000_ref_clk_bound_rate(priv, ref_clk_rate);
if (ret < 0)
return ret;

+ if (priv->dynamic_mode) {
+ /* Default to low-frequency mode to allow for large ratios */
+ priv->lf_ratio = true;
+ } else {
+ /*
+ * set default rate as 1/1.
+ * otherwise .set_rate which setup ratio
+ * is never called if user requests 1/1 rate
+ */
+ ret = __cs2000_set_rate(priv, ch, ref_clk_rate, ref_clk_rate);
+ if (ret < 0)
+ return ret;
+ }
+
parent_names[CLK_IN] = __clk_get_name(priv->clk_in);
parent_names[REF_CLK] = __clk_get_name(priv->ref_clk);

--
2.31.1