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-rw-r--r--drivers/clk/analogbits/Kconfig3
-rw-r--r--drivers/clk/analogbits/Makefile3
-rw-r--r--drivers/clk/analogbits/wrpll-cln28hpc.c368
3 files changed, 374 insertions, 0 deletions
diff --git a/drivers/clk/analogbits/Kconfig b/drivers/clk/analogbits/Kconfig
new file mode 100644
index 0000000000..1e291b1854
--- /dev/null
+++ b/drivers/clk/analogbits/Kconfig
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config CLK_ANALOGBITS_WRPLL_CLN28HPC
+ bool
diff --git a/drivers/clk/analogbits/Makefile b/drivers/clk/analogbits/Makefile
new file mode 100644
index 0000000000..bf01744745
--- /dev/null
+++ b/drivers/clk/analogbits/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_CLK_ANALOGBITS_WRPLL_CLN28HPC) += wrpll-cln28hpc.o
diff --git a/drivers/clk/analogbits/wrpll-cln28hpc.c b/drivers/clk/analogbits/wrpll-cln28hpc.c
new file mode 100644
index 0000000000..09ca823563
--- /dev/null
+++ b/drivers/clk/analogbits/wrpll-cln28hpc.c
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018-2019 SiFive, Inc.
+ * Wesley Terpstra
+ * Paul Walmsley
+ *
+ * This library supports configuration parsing and reprogramming of
+ * the CLN28HPC variant of the Analog Bits Wide Range PLL. The
+ * intention is for this library to be reusable for any device that
+ * integrates this PLL; thus the register structure and programming
+ * details are expected to be provided by a separate IP block driver.
+ *
+ * The bulk of this code is primarily useful for clock configurations
+ * that must operate at arbitrary rates, as opposed to clock configurations
+ * that are restricted by software or manufacturer guidance to a small,
+ * pre-determined set of performance points.
+ *
+ * References:
+ * - Analog Bits "Wide Range PLL Datasheet", version 2015.10.01
+ * - SiFive FU540-C000 Manual v1p0, Chapter 7 "Clocking and Reset"
+ * https://static.dev.sifive.com/FU540-C000-v1.0.pdf
+ */
+
+#include <linux/bug.h>
+#include <linux/err.h>
+#include <linux/limits.h>
+#include <linux/log2.h>
+#include <linux/math64.h>
+#include <linux/math.h>
+#include <linux/minmax.h>
+
+#include <linux/clk/analogbits-wrpll-cln28hpc.h>
+
+/* MIN_INPUT_FREQ: minimum input clock frequency, in Hz (Fref_min) */
+#define MIN_INPUT_FREQ 7000000
+
+/* MAX_INPUT_FREQ: maximum input clock frequency, in Hz (Fref_max) */
+#define MAX_INPUT_FREQ 600000000
+
+/* MIN_POST_DIVIDE_REF_FREQ: minimum post-divider reference frequency, in Hz */
+#define MIN_POST_DIVR_FREQ 7000000
+
+/* MAX_POST_DIVIDE_REF_FREQ: maximum post-divider reference frequency, in Hz */
+#define MAX_POST_DIVR_FREQ 200000000
+
+/* MIN_VCO_FREQ: minimum VCO frequency, in Hz (Fvco_min) */
+#define MIN_VCO_FREQ 2400000000UL
+
+/* MAX_VCO_FREQ: maximum VCO frequency, in Hz (Fvco_max) */
+#define MAX_VCO_FREQ 4800000000ULL
+
+/* MAX_DIVQ_DIVISOR: maximum output divisor. Selected by DIVQ = 6 */
+#define MAX_DIVQ_DIVISOR 64
+
+/* MAX_DIVR_DIVISOR: maximum reference divisor. Selected by DIVR = 63 */
+#define MAX_DIVR_DIVISOR 64
+
+/* MAX_LOCK_US: maximum PLL lock time, in microseconds (tLOCK_max) */
+#define MAX_LOCK_US 70
+
+/*
+ * ROUND_SHIFT: number of bits to shift to avoid precision loss in the rounding
+ * algorithm
+ */
+#define ROUND_SHIFT 20
+
+/*
+ * Private functions
+ */
+
+/**
+ * __wrpll_calc_filter_range() - determine PLL loop filter bandwidth
+ * @post_divr_freq: input clock rate after the R divider
+ *
+ * Select the value to be presented to the PLL RANGE input signals, based
+ * on the input clock frequency after the post-R-divider @post_divr_freq.
+ * This code follows the recommendations in the PLL datasheet for filter
+ * range selection.
+ *
+ * Return: The RANGE value to be presented to the PLL configuration inputs,
+ * or a negative return code upon error.
+ */
+static int __wrpll_calc_filter_range(unsigned long post_divr_freq)
+{
+ if (post_divr_freq < MIN_POST_DIVR_FREQ ||
+ post_divr_freq > MAX_POST_DIVR_FREQ) {
+ WARN(1, "%s: post-divider reference freq out of range: %lu",
+ __func__, post_divr_freq);
+ return -ERANGE;
+ }
+
+ switch (post_divr_freq) {
+ case 0 ... 10999999:
+ return 1;
+ case 11000000 ... 17999999:
+ return 2;
+ case 18000000 ... 29999999:
+ return 3;
+ case 30000000 ... 49999999:
+ return 4;
+ case 50000000 ... 79999999:
+ return 5;
+ case 80000000 ... 129999999:
+ return 6;
+ }
+
+ return 7;
+}
+
+/**
+ * __wrpll_calc_fbdiv() - return feedback fixed divide value
+ * @c: ptr to a struct wrpll_cfg record to read from
+ *
+ * The internal feedback path includes a fixed by-two divider; the
+ * external feedback path does not. Return the appropriate divider
+ * value (2 or 1) depending on whether internal or external feedback
+ * is enabled. This code doesn't test for invalid configurations
+ * (e.g. both or neither of WRPLL_FLAGS_*_FEEDBACK are set); it relies
+ * on the caller to do so.
+ *
+ * Context: Any context. Caller must protect the memory pointed to by
+ * @c from simultaneous modification.
+ *
+ * Return: 2 if internal feedback is enabled or 1 if external feedback
+ * is enabled.
+ */
+static u8 __wrpll_calc_fbdiv(const struct wrpll_cfg *c)
+{
+ return (c->flags & WRPLL_FLAGS_INT_FEEDBACK_MASK) ? 2 : 1;
+}
+
+/**
+ * __wrpll_calc_divq() - determine DIVQ based on target PLL output clock rate
+ * @target_rate: target PLL output clock rate
+ * @vco_rate: pointer to a u64 to store the computed VCO rate into
+ *
+ * Determine a reasonable value for the PLL Q post-divider, based on the
+ * target output rate @target_rate for the PLL. Along with returning the
+ * computed Q divider value as the return value, this function stores the
+ * desired target VCO rate into the variable pointed to by @vco_rate.
+ *
+ * Context: Any context. Caller must protect the memory pointed to by
+ * @vco_rate from simultaneous access or modification.
+ *
+ * Return: a positive integer DIVQ value to be programmed into the hardware
+ * upon success, or 0 upon error (since 0 is an invalid DIVQ value)
+ */
+static u8 __wrpll_calc_divq(u32 target_rate, u64 *vco_rate)
+{
+ u64 s;
+ u8 divq = 0;
+
+ if (!vco_rate) {
+ WARN_ON(1);
+ goto wcd_out;
+ }
+
+ s = div_u64(MAX_VCO_FREQ, target_rate);
+ if (s <= 1) {
+ divq = 1;
+ *vco_rate = MAX_VCO_FREQ;
+ } else if (s > MAX_DIVQ_DIVISOR) {
+ divq = ilog2(MAX_DIVQ_DIVISOR);
+ *vco_rate = MIN_VCO_FREQ;
+ } else {
+ divq = ilog2(s);
+ *vco_rate = (u64)target_rate << divq;
+ }
+
+wcd_out:
+ return divq;
+}
+
+/**
+ * __wrpll_update_parent_rate() - update PLL data when parent rate changes
+ * @c: ptr to a struct wrpll_cfg record to write PLL data to
+ * @parent_rate: PLL input refclk rate (pre-R-divider)
+ *
+ * Pre-compute some data used by the PLL configuration algorithm when
+ * the PLL's reference clock rate changes. The intention is to avoid
+ * computation when the parent rate remains constant - expected to be
+ * the common case.
+ *
+ * Returns: 0 upon success or -ERANGE if the reference clock rate is
+ * out of range.
+ */
+static int __wrpll_update_parent_rate(struct wrpll_cfg *c,
+ unsigned long parent_rate)
+{
+ u8 max_r_for_parent;
+
+ if (parent_rate > MAX_INPUT_FREQ || parent_rate < MIN_POST_DIVR_FREQ)
+ return -ERANGE;
+
+ c->parent_rate = parent_rate;
+ max_r_for_parent = div_u64(parent_rate, MIN_POST_DIVR_FREQ);
+ c->max_r = min_t(u8, MAX_DIVR_DIVISOR, max_r_for_parent);
+
+ c->init_r = DIV_ROUND_UP_ULL(parent_rate, MAX_POST_DIVR_FREQ);
+
+ return 0;
+}
+
+/**
+ * wrpll_configure_for_rate() - compute PLL configuration for a target rate
+ * @c: ptr to a struct wrpll_cfg record to write into
+ * @target_rate: target PLL output clock rate (post-Q-divider)
+ * @parent_rate: PLL input refclk rate (pre-R-divider)
+ *
+ * Compute the appropriate PLL signal configuration values and store
+ * in PLL context @c. PLL reprogramming is not glitchless, so the
+ * caller should switch any downstream logic to a different clock
+ * source or clock-gate it before presenting these values to the PLL
+ * configuration signals.
+ *
+ * The caller must pass this function a pre-initialized struct
+ * wrpll_cfg record: either initialized to zero (with the
+ * exception of the .name and .flags fields) or read from the PLL.
+ *
+ * Context: Any context. Caller must protect the memory pointed to by @c
+ * from simultaneous access or modification.
+ *
+ * Return: 0 upon success; anything else upon failure.
+ */
+int wrpll_configure_for_rate(struct wrpll_cfg *c, u32 target_rate,
+ unsigned long parent_rate)
+{
+ unsigned long ratio;
+ u64 target_vco_rate, delta, best_delta, f_pre_div, vco, vco_pre;
+ u32 best_f, f, post_divr_freq;
+ u8 fbdiv, divq, best_r, r;
+ int range;
+
+ if (c->flags == 0) {
+ WARN(1, "%s called with uninitialized PLL config", __func__);
+ return -EINVAL;
+ }
+
+ /* Initialize rounding data if it hasn't been initialized already */
+ if (parent_rate != c->parent_rate) {
+ if (__wrpll_update_parent_rate(c, parent_rate)) {
+ pr_err("%s: PLL input rate is out of range\n",
+ __func__);
+ return -ERANGE;
+ }
+ }
+
+ c->flags &= ~WRPLL_FLAGS_RESET_MASK;
+
+ /* Put the PLL into bypass if the user requests the parent clock rate */
+ if (target_rate == parent_rate) {
+ c->flags |= WRPLL_FLAGS_BYPASS_MASK;
+ return 0;
+ }
+
+ c->flags &= ~WRPLL_FLAGS_BYPASS_MASK;
+
+ /* Calculate the Q shift and target VCO rate */
+ divq = __wrpll_calc_divq(target_rate, &target_vco_rate);
+ if (!divq)
+ return -1;
+ c->divq = divq;
+
+ /* Precalculate the pre-Q divider target ratio */
+ ratio = div64_u64((target_vco_rate << ROUND_SHIFT), parent_rate);
+
+ fbdiv = __wrpll_calc_fbdiv(c);
+ best_r = 0;
+ best_f = 0;
+ best_delta = MAX_VCO_FREQ;
+
+ /*
+ * Consider all values for R which land within
+ * [MIN_POST_DIVR_FREQ, MAX_POST_DIVR_FREQ]; prefer smaller R
+ */
+ for (r = c->init_r; r <= c->max_r; ++r) {
+ f_pre_div = ratio * r;
+ f = (f_pre_div + (1 << ROUND_SHIFT)) >> ROUND_SHIFT;
+ f >>= (fbdiv - 1);
+
+ post_divr_freq = div_u64(parent_rate, r);
+ vco_pre = fbdiv * post_divr_freq;
+ vco = vco_pre * f;
+
+ /* Ensure rounding didn't take us out of range */
+ if (vco > target_vco_rate) {
+ --f;
+ vco = vco_pre * f;
+ } else if (vco < MIN_VCO_FREQ) {
+ ++f;
+ vco = vco_pre * f;
+ }
+
+ delta = abs(target_rate - vco);
+ if (delta < best_delta) {
+ best_delta = delta;
+ best_r = r;
+ best_f = f;
+ }
+ }
+
+ c->divr = best_r - 1;
+ c->divf = best_f - 1;
+
+ post_divr_freq = div_u64(parent_rate, best_r);
+
+ /* Pick the best PLL jitter filter */
+ range = __wrpll_calc_filter_range(post_divr_freq);
+ if (range < 0)
+ return range;
+ c->range = range;
+
+ return 0;
+}
+
+/**
+ * wrpll_calc_output_rate() - calculate the PLL's target output rate
+ * @c: ptr to a struct wrpll_cfg record to read from
+ * @parent_rate: PLL refclk rate
+ *
+ * Given a pointer to the PLL's current input configuration @c and the
+ * PLL's input reference clock rate @parent_rate (before the R
+ * pre-divider), calculate the PLL's output clock rate (after the Q
+ * post-divider).
+ *
+ * Context: Any context. Caller must protect the memory pointed to by @c
+ * from simultaneous modification.
+ *
+ * Return: the PLL's output clock rate, in Hz. The return value from
+ * this function is intended to be convenient to pass directly
+ * to the Linux clock framework; thus there is no explicit
+ * error return value.
+ */
+unsigned long wrpll_calc_output_rate(const struct wrpll_cfg *c,
+ unsigned long parent_rate)
+{
+ u8 fbdiv;
+ u64 n;
+
+ if (c->flags & WRPLL_FLAGS_EXT_FEEDBACK_MASK) {
+ WARN(1, "external feedback mode not yet supported");
+ return ULONG_MAX;
+ }
+
+ fbdiv = __wrpll_calc_fbdiv(c);
+ n = parent_rate * fbdiv * (c->divf + 1);
+ n = div_u64(n, c->divr + 1);
+ n >>= c->divq;
+
+ return n;
+}
+
+/**
+ * wrpll_calc_max_lock_us() - return the time for the PLL to lock
+ * @c: ptr to a struct wrpll_cfg record to read from
+ *
+ * Return the minimum amount of time (in microseconds) that the caller
+ * must wait after reprogramming the PLL to ensure that it is locked
+ * to the input frequency and stable. This is likely to depend on the DIVR
+ * value; this is under discussion with the manufacturer.
+ *
+ * Return: the minimum amount of time the caller must wait for the PLL
+ * to lock (in microseconds)
+ */
+unsigned int wrpll_calc_max_lock_us(const struct wrpll_cfg *c)
+{
+ return MAX_LOCK_US;
+}
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