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linux/drivers/pwm/pwm-mediatek.c
Sean Wang 04c0a4e00d pwm: mediatek: Improve precision in rate calculation 
Add a way that turning resolution from in nanosecond into in picosecond
to improve noticeably almost 4.5% precision.

It's necessary to hold the new resolution with type u64 and thus related
operations on u64 are applied instead in those rate calculations.

And the patch has a dependency on [1].

[1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html

Cc: stable@vger.kernel.org
Fixes: caf065f8fd ("pwm: Add MediaTek PWM support")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2018-03-28 00:32:25 +02:00

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/*
* Mediatek Pulse Width Modulator driver
*
* Copyright (C) 2015 John Crispin <blogic@openwrt.org>
* Copyright (C) 2017 Zhi Mao <zhi.mao@mediatek.com>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/err.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/clk.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/types.h>
/* PWM registers and bits definitions */
#define PWMCON 0x00
#define PWMHDUR 0x04
#define PWMLDUR 0x08
#define PWMGDUR 0x0c
#define PWMWAVENUM 0x28
#define PWMDWIDTH 0x2c
#define PWM45DWIDTH_FIXUP 0x30
#define PWMTHRES 0x30
#define PWM45THRES_FIXUP 0x34
#define PWM_CLK_DIV_MAX 7
enum {
MTK_CLK_MAIN = 0,
MTK_CLK_TOP,
MTK_CLK_PWM1,
MTK_CLK_PWM2,
MTK_CLK_PWM3,
MTK_CLK_PWM4,
MTK_CLK_PWM5,
MTK_CLK_PWM6,
MTK_CLK_PWM7,
MTK_CLK_PWM8,
MTK_CLK_MAX,
};
static const char * const mtk_pwm_clk_name[MTK_CLK_MAX] = {
"main", "top", "pwm1", "pwm2", "pwm3", "pwm4", "pwm5", "pwm6", "pwm7",
"pwm8"
};
struct mtk_pwm_platform_data {
unsigned int num_pwms;
bool pwm45_fixup;
};
/**
* struct mtk_pwm_chip - struct representing PWM chip
* @chip: linux PWM chip representation
* @regs: base address of PWM chip
* @clks: list of clocks
*/
struct mtk_pwm_chip {
struct pwm_chip chip;
void __iomem *regs;
struct clk *clks[MTK_CLK_MAX];
const struct mtk_pwm_platform_data *soc;
};
static const unsigned int mtk_pwm_reg_offset[] = {
0x0010, 0x0050, 0x0090, 0x00d0, 0x0110, 0x0150, 0x0190, 0x0220
};
static inline struct mtk_pwm_chip *to_mtk_pwm_chip(struct pwm_chip *chip)
{
return container_of(chip, struct mtk_pwm_chip, chip);
}
static int mtk_pwm_clk_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
int ret;
ret = clk_prepare_enable(pc->clks[MTK_CLK_TOP]);
if (ret < 0)
return ret;
ret = clk_prepare_enable(pc->clks[MTK_CLK_MAIN]);
if (ret < 0)
goto disable_clk_top;
ret = clk_prepare_enable(pc->clks[MTK_CLK_PWM1 + pwm->hwpwm]);
if (ret < 0)
goto disable_clk_main;
return 0;
disable_clk_main:
clk_disable_unprepare(pc->clks[MTK_CLK_MAIN]);
disable_clk_top:
clk_disable_unprepare(pc->clks[MTK_CLK_TOP]);
return ret;
}
static void mtk_pwm_clk_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
clk_disable_unprepare(pc->clks[MTK_CLK_PWM1 + pwm->hwpwm]);
clk_disable_unprepare(pc->clks[MTK_CLK_MAIN]);
clk_disable_unprepare(pc->clks[MTK_CLK_TOP]);
}
static inline u32 mtk_pwm_readl(struct mtk_pwm_chip *chip, unsigned int num,
unsigned int offset)
{
return readl(chip->regs + mtk_pwm_reg_offset[num] + offset);
}
static inline void mtk_pwm_writel(struct mtk_pwm_chip *chip,
unsigned int num, unsigned int offset,
u32 value)
{
writel(value, chip->regs + mtk_pwm_reg_offset[num] + offset);
}
static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
reg_thres = PWMTHRES;
u64 resolution;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
/* Using resolution in picosecond gets accuracy higher */
resolution = (u64)NSEC_PER_SEC * 1000;
do_div(resolution, clk_get_rate(clk));
cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
while (cnt_period > 8191) {
resolution *= 2;
clkdiv++;
cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
resolution);
}
if (clkdiv > PWM_CLK_DIV_MAX) {
mtk_pwm_clk_disable(chip, pwm);
dev_err(chip->dev, "period %d not supported\n", period_ns);
return -EINVAL;
}
if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
/*
* PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
* from the other PWMs on MT7623.
*/
reg_width = PWM45DWIDTH_FIXUP;
reg_thres = PWM45THRES_FIXUP;
}
cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
mtk_pwm_writel(pc, pwm->hwpwm, reg_width, cnt_period);
mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
mtk_pwm_clk_disable(chip, pwm);
return 0;
}
static int mtk_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
u32 value;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
value = readl(pc->regs);
value |= BIT(pwm->hwpwm);
writel(value, pc->regs);
return 0;
}
static void mtk_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
u32 value;
value = readl(pc->regs);
value &= ~BIT(pwm->hwpwm);
writel(value, pc->regs);
mtk_pwm_clk_disable(chip, pwm);
}
static const struct pwm_ops mtk_pwm_ops = {
.config = mtk_pwm_config,
.enable = mtk_pwm_enable,
.disable = mtk_pwm_disable,
.owner = THIS_MODULE,
};
static int mtk_pwm_probe(struct platform_device *pdev)
{
const struct mtk_pwm_platform_data *data;
struct mtk_pwm_chip *pc;
struct resource *res;
unsigned int i;
int ret;
pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
if (!pc)
return -ENOMEM;
data = of_device_get_match_data(&pdev->dev);
if (data == NULL)
return -EINVAL;
pc->soc = data;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
pc->regs = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(pc->regs))
return PTR_ERR(pc->regs);
for (i = 0; i < data->num_pwms + 2; i++) {
pc->clks[i] = devm_clk_get(&pdev->dev, mtk_pwm_clk_name[i]);
if (IS_ERR(pc->clks[i])) {
dev_err(&pdev->dev, "clock: %s fail: %ld\n",
mtk_pwm_clk_name[i], PTR_ERR(pc->clks[i]));
return PTR_ERR(pc->clks[i]);
}
}
platform_set_drvdata(pdev, pc);
pc->chip.dev = &pdev->dev;
pc->chip.ops = &mtk_pwm_ops;
pc->chip.base = -1;
pc->chip.npwm = data->num_pwms;
ret = pwmchip_add(&pc->chip);
if (ret < 0) {
dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
return ret;
}
return 0;
}
static int mtk_pwm_remove(struct platform_device *pdev)
{
struct mtk_pwm_chip *pc = platform_get_drvdata(pdev);
return pwmchip_remove(&pc->chip);
}
static const struct mtk_pwm_platform_data mt2712_pwm_data = {
.num_pwms = 8,
.pwm45_fixup = false,
};
static const struct mtk_pwm_platform_data mt7622_pwm_data = {
.num_pwms = 6,
.pwm45_fixup = false,
};
static const struct mtk_pwm_platform_data mt7623_pwm_data = {
.num_pwms = 5,
.pwm45_fixup = true,
};
static const struct of_device_id mtk_pwm_of_match[] = {
{ .compatible = "mediatek,mt2712-pwm", .data = &mt2712_pwm_data },
{ .compatible = "mediatek,mt7622-pwm", .data = &mt7622_pwm_data },
{ .compatible = "mediatek,mt7623-pwm", .data = &mt7623_pwm_data },
{ },
};
MODULE_DEVICE_TABLE(of, mtk_pwm_of_match);
static struct platform_driver mtk_pwm_driver = {
.driver = {
.name = "mtk-pwm",
.of_match_table = mtk_pwm_of_match,
},
.probe = mtk_pwm_probe,
.remove = mtk_pwm_remove,
};
module_platform_driver(mtk_pwm_driver);
MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
MODULE_LICENSE("GPL");
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