diff options
| -rw-r--r-- | MAINTAINERS | 6 | ||||
| -rw-r--r-- | drivers/clk/Kconfig | 2 | ||||
| -rw-r--r-- | drivers/clk/Makefile | 1 | ||||
| -rw-r--r-- | drivers/clk/analogbits/Kconfig | 2 | ||||
| -rw-r--r-- | drivers/clk/analogbits/Makefile | 3 | ||||
| -rw-r--r-- | drivers/clk/analogbits/wrpll-cln28hpc.c | 364 | ||||
| -rw-r--r-- | include/linux/clk/analogbits-wrpll-cln28hpc.h | 79 |
7 files changed, 457 insertions, 0 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index 09f43f1bdd15..98e1d15549f5 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -960,6 +960,12 @@ F: drivers/iio/adc/ltc2497* X: drivers/iio/*/adjd* F: drivers/staging/iio/*/ad* +ANALOGBITS PLL LIBRARIES +M: Paul Walmsley <paul.walmsley@sifive.com> +S: Supported +F: drivers/clk/analogbits/* +F: include/linux/clk/analogbits* + ANDES ARCHITECTURE M: Greentime Hu <green.hu@gmail.com> M: Vincent Chen <deanbo422@gmail.com> diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig index e705aab9e38b..8a0e77f791ab 100644 --- a/drivers/clk/Kconfig +++ b/drivers/clk/Kconfig @@ -1,3 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0 config CLKDEV_LOOKUP bool @@ -297,6 +298,7 @@ config COMMON_CLK_FIXED_MMIO Support for Memory Mapped IO Fixed clocks source "drivers/clk/actions/Kconfig" +source "drivers/clk/analogbits/Kconfig" source "drivers/clk/bcm/Kconfig" source "drivers/clk/hisilicon/Kconfig" source "drivers/clk/imgtec/Kconfig" diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 1db133652f0c..091ee1d8af65 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -64,6 +64,7 @@ obj-$(CONFIG_COMMON_CLK_XGENE) += clk-xgene.o # please keep this section sorted lexicographically by directory path name obj-y += actions/ +obj-y += analogbits/ obj-$(CONFIG_COMMON_CLK_AT91) += at91/ obj-$(CONFIG_ARCH_ARTPEC) += axis/ obj-$(CONFIG_ARC_PLAT_AXS10X) += axs10x/ diff --git a/drivers/clk/analogbits/Kconfig b/drivers/clk/analogbits/Kconfig new file mode 100644 index 000000000000..b5fd60c7f136 --- /dev/null +++ b/drivers/clk/analogbits/Kconfig @@ -0,0 +1,2 @@ +config CLK_ANALOGBITS_WRPLL_CLN28HPC + bool diff --git a/drivers/clk/analogbits/Makefile b/drivers/clk/analogbits/Makefile new file mode 100644 index 000000000000..bf017447451e --- /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 000000000000..776ead319ae9 --- /dev/null +++ b/drivers/clk/analogbits/wrpll-cln28hpc.c @@ -0,0 +1,364 @@ +// 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/log2.h> +#include <linux/math64.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() - 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; +} diff --git a/include/linux/clk/analogbits-wrpll-cln28hpc.h b/include/linux/clk/analogbits-wrpll-cln28hpc.h new file mode 100644 index 000000000000..03279097e138 --- /dev/null +++ b/include/linux/clk/analogbits-wrpll-cln28hpc.h @@ -0,0 +1,79 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2018-2019 SiFive, Inc. + * Wesley Terpstra + * Paul Walmsley + */ + +#ifndef __LINUX_CLK_ANALOGBITS_WRPLL_CLN28HPC_H +#define __LINUX_CLK_ANALOGBITS_WRPLL_CLN28HPC_H + +#include <linux/types.h> + +/* DIVQ_VALUES: number of valid DIVQ values */ +#define DIVQ_VALUES 6 + +/* + * Bit definitions for struct wrpll_cfg.flags + * + * WRPLL_FLAGS_BYPASS_FLAG: if set, the PLL is either in bypass, or should be + * programmed to enter bypass + * WRPLL_FLAGS_RESET_FLAG: if set, the PLL is in reset + * WRPLL_FLAGS_INT_FEEDBACK_FLAG: if set, the PLL is configured for internal + * feedback mode + * WRPLL_FLAGS_EXT_FEEDBACK_FLAG: if set, the PLL is configured for external + * feedback mode (not yet supported by this driver) + */ +#define WRPLL_FLAGS_BYPASS_SHIFT 0 +#define WRPLL_FLAGS_BYPASS_MASK BIT(WRPLL_FLAGS_BYPASS_SHIFT) +#define WRPLL_FLAGS_RESET_SHIFT 1 +#define WRPLL_FLAGS_RESET_MASK BIT(WRPLL_FLAGS_RESET_SHIFT) +#define WRPLL_FLAGS_INT_FEEDBACK_SHIFT 2 +#define WRPLL_FLAGS_INT_FEEDBACK_MASK BIT(WRPLL_FLAGS_INT_FEEDBACK_SHIFT) +#define WRPLL_FLAGS_EXT_FEEDBACK_SHIFT 3 +#define WRPLL_FLAGS_EXT_FEEDBACK_MASK BIT(WRPLL_FLAGS_EXT_FEEDBACK_SHIFT) + +/** + * struct wrpll_cfg - WRPLL configuration values + * @divr: reference divider value (6 bits), as presented to the PLL signals + * @divf: feedback divider value (9 bits), as presented to the PLL signals + * @divq: output divider value (3 bits), as presented to the PLL signals + * @flags: PLL configuration flags. See above for more information + * @range: PLL loop filter range. See below for more information + * @output_rate_cache: cached output rates, swept across DIVQ + * @parent_rate: PLL refclk rate for which values are valid + * @max_r: maximum possible R divider value, given @parent_rate + * @init_r: initial R divider value to start the search from + * + * @divr, @divq, @divq, @range represent what the PLL expects to see + * on its input signals. Thus @divr and @divf are the actual divisors + * minus one. @divq is a power-of-two divider; for example, 1 = + * divide-by-2 and 6 = divide-by-64. 0 is an invalid @divq value. + * + * When initially passing a struct wrpll_cfg record, the + * record should be zero-initialized with the exception of the @flags + * field. The only flag bits that need to be set are either + * WRPLL_FLAGS_INT_FEEDBACK or WRPLL_FLAGS_EXT_FEEDBACK. + */ +struct wrpll_cfg { + u8 divr; + u8 divq; + u8 range; + u8 flags; + u16 divf; +/* private: */ + u32 output_rate_cache[DIVQ_VALUES]; + unsigned long parent_rate; + u8 max_r; + u8 init_r; +}; + +int wrpll_configure_for_rate(struct wrpll_cfg *c, u32 target_rate, + unsigned long parent_rate); + +unsigned int wrpll_calc_max_lock_us(const struct wrpll_cfg *c); + +unsigned long wrpll_calc_output_rate(const struct wrpll_cfg *c, + unsigned long parent_rate); + +#endif /* __LINUX_CLK_ANALOGBITS_WRPLL_CLN28HPC_H */ |