drivers/clk/mmp/clk-frac.c

Source file repositories/reference/linux-study-clean/drivers/clk/mmp/clk-frac.c

File Facts

System
Linux kernel
Corpus path
drivers/clk/mmp/clk-frac.c
Extension
.c
Size
4960 bytes
Lines
207
Domain
Driver Families
Bucket
drivers/clk
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * mmp factor clock operation source file
 *
 * Copyright (C) 2012 Marvell
 * Chao Xie <xiechao.mail@gmail.com>
 */

#include <linux/clk-provider.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/err.h>

#include "clk.h"
/*
 * It is M/N clock
 *
 * Fout from synthesizer can be given from two equations:
 * numerator/denominator = Fin / (Fout * factor)
 */

#define to_clk_factor(hw) container_of(hw, struct mmp_clk_factor, hw)

static int clk_factor_determine_rate(struct clk_hw *hw,
				     struct clk_rate_request *req)
{
	struct mmp_clk_factor *factor = to_clk_factor(hw);
	u64 rate = 0, prev_rate;
	struct u32_fract *d;
	int i;

	for (i = 0; i < factor->ftbl_cnt; i++) {
		d = &factor->ftbl[i];

		prev_rate = rate;
		rate = (u64)(req->best_parent_rate) * d->denominator;
		do_div(rate, d->numerator * factor->masks->factor);
		if (rate > req->rate)
			break;
	}

	if ((i == 0) || (i == factor->ftbl_cnt))
		req->rate = rate;
	else if ((req->rate - prev_rate) > (rate - req->rate))
		req->rate = rate;
	else
		req->rate = prev_rate;

	return 0;
}

static unsigned long clk_factor_recalc_rate(struct clk_hw *hw,
		unsigned long parent_rate)
{
	struct mmp_clk_factor *factor = to_clk_factor(hw);
	struct mmp_clk_factor_masks *masks = factor->masks;
	struct u32_fract d;
	unsigned int val;
	u64 rate;

	val = readl_relaxed(factor->base);

	/* calculate numerator */
	d.numerator = (val >> masks->num_shift) & masks->num_mask;

	/* calculate denominator */
	d.denominator = (val >> masks->den_shift) & masks->den_mask;
	if (!d.denominator)
		return 0;

	rate = (u64)parent_rate * d.denominator;
	do_div(rate, d.numerator * factor->masks->factor);

	return rate;
}

/* Configures new clock rate*/
static int clk_factor_set_rate(struct clk_hw *hw, unsigned long drate,
				unsigned long prate)
{
	struct mmp_clk_factor *factor = to_clk_factor(hw);
	struct mmp_clk_factor_masks *masks = factor->masks;
	int i;
	unsigned long val;
	unsigned long flags = 0;
	struct u32_fract *d;
	u64 rate = 0;

	for (i = 0; i < factor->ftbl_cnt; i++) {
		d = &factor->ftbl[i];

Annotation

Implementation Notes