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15d4dbd601
linux-next/drivers/pwm/pwm-imx27.c
Uwe Kleine-König 15d4dbd601 pwm: imx27: Fix clock handling in pwm_imx27_apply() 
pwm_imx27_apply() enables the clocks if the previous PWM state was
disabled. Given that the clocks are supposed to be left on iff the PWM
is running, the decision to disable the clocks at the end of the
function must not depend on the previous state.

Without this fix the enable count of the two affected clocks increases
by one whenever ->apply() changes from one disabled state to another.

Fixes: bd88d319ab ("pwm: imx27: Unconditionally write state to hardware")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2020-03-30 16:55:25 +02:00

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9.2 KiB
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// SPDX-License-Identifier: GPL-2.0
/*
* simple driver for PWM (Pulse Width Modulator) controller
*
* Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
*
* Limitations:
* - When disabled the output is driven to 0 independent of the configured
* polarity.
*/
#include <linux/bitfield.h>
#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#define MX3_PWMCR 0x00 /* PWM Control Register */
#define MX3_PWMSR 0x04 /* PWM Status Register */
#define MX3_PWMSAR 0x0C /* PWM Sample Register */
#define MX3_PWMPR 0x10 /* PWM Period Register */
#define MX3_PWMCR_FWM GENMASK(27, 26)
#define MX3_PWMCR_STOPEN BIT(25)
#define MX3_PWMCR_DOZEN BIT(24)
#define MX3_PWMCR_WAITEN BIT(23)
#define MX3_PWMCR_DBGEN BIT(22)
#define MX3_PWMCR_BCTR BIT(21)
#define MX3_PWMCR_HCTR BIT(20)
#define MX3_PWMCR_POUTC GENMASK(19, 18)
#define MX3_PWMCR_POUTC_NORMAL 0
#define MX3_PWMCR_POUTC_INVERTED 1
#define MX3_PWMCR_POUTC_OFF 2
#define MX3_PWMCR_CLKSRC GENMASK(17, 16)
#define MX3_PWMCR_CLKSRC_OFF 0
#define MX3_PWMCR_CLKSRC_IPG 1
#define MX3_PWMCR_CLKSRC_IPG_HIGH 2
#define MX3_PWMCR_CLKSRC_IPG_32K 3
#define MX3_PWMCR_PRESCALER GENMASK(15, 4)
#define MX3_PWMCR_SWR BIT(3)
#define MX3_PWMCR_REPEAT GENMASK(2, 1)
#define MX3_PWMCR_REPEAT_1X 0
#define MX3_PWMCR_REPEAT_2X 1
#define MX3_PWMCR_REPEAT_4X 2
#define MX3_PWMCR_REPEAT_8X 3
#define MX3_PWMCR_EN BIT(0)
#define MX3_PWMSR_FWE BIT(6)
#define MX3_PWMSR_CMP BIT(5)
#define MX3_PWMSR_ROV BIT(4)
#define MX3_PWMSR_FE BIT(3)
#define MX3_PWMSR_FIFOAV GENMASK(2, 0)
#define MX3_PWMSR_FIFOAV_EMPTY 0
#define MX3_PWMSR_FIFOAV_1WORD 1
#define MX3_PWMSR_FIFOAV_2WORDS 2
#define MX3_PWMSR_FIFOAV_3WORDS 3
#define MX3_PWMSR_FIFOAV_4WORDS 4
#define MX3_PWMCR_PRESCALER_SET(x) FIELD_PREP(MX3_PWMCR_PRESCALER, (x) - 1)
#define MX3_PWMCR_PRESCALER_GET(x) (FIELD_GET(MX3_PWMCR_PRESCALER, \
(x)) + 1)
#define MX3_PWM_SWR_LOOP 5
/* PWMPR register value of 0xffff has the same effect as 0xfffe */
#define MX3_PWMPR_MAX 0xfffe
struct pwm_imx27_chip {
struct clk *clk_ipg;
struct clk *clk_per;
void __iomem *mmio_base;
struct pwm_chip chip;
/*
* The driver cannot read the current duty cycle from the hardware if
* the hardware is disabled. Cache the last programmed duty cycle
* value to return in that case.
*/
unsigned int duty_cycle;
};
#define to_pwm_imx27_chip(chip) container_of(chip, struct pwm_imx27_chip, chip)
static int pwm_imx27_clk_prepare_enable(struct pwm_chip *chip)
{
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
int ret;
ret = clk_prepare_enable(imx->clk_ipg);
if (ret)
return ret;
ret = clk_prepare_enable(imx->clk_per);
if (ret) {
clk_disable_unprepare(imx->clk_ipg);
return ret;
}
return 0;
}
static void pwm_imx27_clk_disable_unprepare(struct pwm_chip *chip)
{
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
clk_disable_unprepare(imx->clk_per);
clk_disable_unprepare(imx->clk_ipg);
}
static void pwm_imx27_get_state(struct pwm_chip *chip,
struct pwm_device *pwm, struct pwm_state *state)
{
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
u32 period, prescaler, pwm_clk, val;
u64 tmp;
int ret;
ret = pwm_imx27_clk_prepare_enable(chip);
if (ret < 0)
return;
val = readl(imx->mmio_base + MX3_PWMCR);
if (val & MX3_PWMCR_EN)
state->enabled = true;
else
state->enabled = false;
switch (FIELD_GET(MX3_PWMCR_POUTC, val)) {
case MX3_PWMCR_POUTC_NORMAL:
state->polarity = PWM_POLARITY_NORMAL;
break;
case MX3_PWMCR_POUTC_INVERTED:
state->polarity = PWM_POLARITY_INVERSED;
break;
default:
dev_warn(chip->dev, "can't set polarity, output disconnected");
}
prescaler = MX3_PWMCR_PRESCALER_GET(val);
pwm_clk = clk_get_rate(imx->clk_per);
pwm_clk = DIV_ROUND_CLOSEST_ULL(pwm_clk, prescaler);
val = readl(imx->mmio_base + MX3_PWMPR);
period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
/* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */
tmp = NSEC_PER_SEC * (u64)(period + 2);
state->period = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
/*
* PWMSAR can be read only if PWM is enabled. If the PWM is disabled,
* use the cached value.
*/
if (state->enabled)
val = readl(imx->mmio_base + MX3_PWMSAR);
else
val = imx->duty_cycle;
tmp = NSEC_PER_SEC * (u64)(val);
state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
if (!state->enabled)
pwm_imx27_clk_disable_unprepare(chip);
}
static void pwm_imx27_sw_reset(struct pwm_chip *chip)
{
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
struct device *dev = chip->dev;
int wait_count = 0;
u32 cr;
writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR);
do {
usleep_range(200, 1000);
cr = readl(imx->mmio_base + MX3_PWMCR);
} while ((cr & MX3_PWMCR_SWR) &&
(wait_count++ < MX3_PWM_SWR_LOOP));
if (cr & MX3_PWMCR_SWR)
dev_warn(dev, "software reset timeout\n");
}
static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
struct pwm_device *pwm)
{
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
struct device *dev = chip->dev;
unsigned int period_ms;
int fifoav;
u32 sr;
sr = readl(imx->mmio_base + MX3_PWMSR);
fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr);
if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
period_ms = DIV_ROUND_UP(pwm_get_period(pwm),
NSEC_PER_MSEC);
msleep(period_ms);
sr = readl(imx->mmio_base + MX3_PWMSR);
if (fifoav == FIELD_GET(MX3_PWMSR_FIFOAV, sr))
dev_warn(dev, "there is no free FIFO slot\n");
}
}
static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
unsigned long period_cycles, duty_cycles, prescale;
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
struct pwm_state cstate;
unsigned long long c;
int ret;
u32 cr;
pwm_get_state(pwm, &cstate);
c = clk_get_rate(imx->clk_per);
c *= state->period;
do_div(c, 1000000000);
period_cycles = c;
prescale = period_cycles / 0x10000 + 1;
period_cycles /= prescale;
c = (unsigned long long)period_cycles * state->duty_cycle;
do_div(c, state->period);
duty_cycles = c;
/*
* according to imx pwm RM, the real period value should be PERIOD
* value in PWMPR plus 2.
*/
if (period_cycles > 2)
period_cycles -= 2;
else
period_cycles = 0;
/*
* Wait for a free FIFO slot if the PWM is already enabled, and flush
* the FIFO if the PWM was disabled and is about to be enabled.
*/
if (cstate.enabled) {
pwm_imx27_wait_fifo_slot(chip, pwm);
} else {
ret = pwm_imx27_clk_prepare_enable(chip);
if (ret)
return ret;
pwm_imx27_sw_reset(chip);
}
writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
writel(period_cycles, imx->mmio_base + MX3_PWMPR);
/*
* Store the duty cycle for future reference in cases where the
* MX3_PWMSAR register can't be read (i.e. when the PWM is disabled).
*/
imx->duty_cycle = duty_cycles;
cr = MX3_PWMCR_PRESCALER_SET(prescale) |
MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) |
MX3_PWMCR_DBGEN;
if (state->polarity == PWM_POLARITY_INVERSED)
cr |= FIELD_PREP(MX3_PWMCR_POUTC,
MX3_PWMCR_POUTC_INVERTED);
if (state->enabled)
cr |= MX3_PWMCR_EN;
writel(cr, imx->mmio_base + MX3_PWMCR);
if (!state->enabled)
pwm_imx27_clk_disable_unprepare(chip);
return 0;
}
static const struct pwm_ops pwm_imx27_ops = {
.apply = pwm_imx27_apply,
.get_state = pwm_imx27_get_state,
.owner = THIS_MODULE,
};
static const struct of_device_id pwm_imx27_dt_ids[] = {
{ .compatible = "fsl,imx27-pwm", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pwm_imx27_dt_ids);
static int pwm_imx27_probe(struct platform_device *pdev)
{
struct pwm_imx27_chip *imx;
imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
if (imx == NULL)
return -ENOMEM;
platform_set_drvdata(pdev, imx);
imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
if (IS_ERR(imx->clk_ipg)) {
int ret = PTR_ERR(imx->clk_ipg);
if (ret != -EPROBE_DEFER)
dev_err(&pdev->dev,
"getting ipg clock failed with %d\n",
ret);
return ret;
}
imx->clk_per = devm_clk_get(&pdev->dev, "per");
if (IS_ERR(imx->clk_per)) {
int ret = PTR_ERR(imx->clk_per);
if (ret != -EPROBE_DEFER)
dev_err(&pdev->dev,
"failed to get peripheral clock: %d\n",
ret);
return ret;
}
imx->chip.ops = &pwm_imx27_ops;
imx->chip.dev = &pdev->dev;
imx->chip.base = -1;
imx->chip.npwm = 1;
imx->chip.of_xlate = of_pwm_xlate_with_flags;
imx->chip.of_pwm_n_cells = 3;
imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(imx->mmio_base))
return PTR_ERR(imx->mmio_base);
return pwmchip_add(&imx->chip);
}
static int pwm_imx27_remove(struct platform_device *pdev)
{
struct pwm_imx27_chip *imx;
imx = platform_get_drvdata(pdev);
pwm_imx27_clk_disable_unprepare(&imx->chip);
return pwmchip_remove(&imx->chip);
}
static struct platform_driver imx_pwm_driver = {
.driver = {
.name = "pwm-imx27",
.of_match_table = pwm_imx27_dt_ids,
},
.probe = pwm_imx27_probe,
.remove = pwm_imx27_remove,
};
module_platform_driver(imx_pwm_driver);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
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