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linux/drivers/pwm/pwm-zx.c
Uwe Kleine-König 71523d1812 pwm: Ensure pwm_apply_state() doesn't modify the state argument 
It is surprising for a PWM consumer when the variable holding the
requested state is modified by pwm_apply_state(). Consider for example a
driver doing:

        #define PERIOD 5000000
        #define DUTY_LITTLE 10
        ...
        struct pwm_state state = {
                .period = PERIOD,
                .duty_cycle = DUTY_LITTLE,
                .polarity = PWM_POLARITY_NORMAL,
                .enabled = true,
        };

        pwm_apply_state(mypwm, &state);
        ...
        state.duty_cycle = PERIOD / 2;
        pwm_apply_state(mypwm, &state);

For sure the second call to pwm_apply_state() should still have
state.period = PERIOD and not something the hardware driver chose for a
reason that doesn't necessarily apply to the second call.

So declare the state argument as a pointer to a const type and adapt all
drivers' .apply callbacks.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2019-09-21 03:25:10 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017 Sanechips Technology Co., Ltd.
* Copyright 2017 Linaro Ltd.
*/
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#define ZX_PWM_MODE 0x0
#define ZX_PWM_CLKDIV_SHIFT 2
#define ZX_PWM_CLKDIV_MASK GENMASK(11, 2)
#define ZX_PWM_CLKDIV(x) (((x) << ZX_PWM_CLKDIV_SHIFT) & \
ZX_PWM_CLKDIV_MASK)
#define ZX_PWM_POLAR BIT(1)
#define ZX_PWM_EN BIT(0)
#define ZX_PWM_PERIOD 0x4
#define ZX_PWM_DUTY 0x8
#define ZX_PWM_CLKDIV_MAX 1023
#define ZX_PWM_PERIOD_MAX 65535
struct zx_pwm_chip {
struct pwm_chip chip;
struct clk *pclk;
struct clk *wclk;
void __iomem *base;
};
static inline struct zx_pwm_chip *to_zx_pwm_chip(struct pwm_chip *chip)
{
return container_of(chip, struct zx_pwm_chip, chip);
}
static inline u32 zx_pwm_readl(struct zx_pwm_chip *zpc, unsigned int hwpwm,
unsigned int offset)
{
return readl(zpc->base + (hwpwm + 1) * 0x10 + offset);
}
static inline void zx_pwm_writel(struct zx_pwm_chip *zpc, unsigned int hwpwm,
unsigned int offset, u32 value)
{
writel(value, zpc->base + (hwpwm + 1) * 0x10 + offset);
}
static void zx_pwm_set_mask(struct zx_pwm_chip *zpc, unsigned int hwpwm,
unsigned int offset, u32 mask, u32 value)
{
u32 data;
data = zx_pwm_readl(zpc, hwpwm, offset);
data &= ~mask;
data |= value & mask;
zx_pwm_writel(zpc, hwpwm, offset, data);
}
static void zx_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct zx_pwm_chip *zpc = to_zx_pwm_chip(chip);
unsigned long rate;
unsigned int div;
u32 value;
u64 tmp;
value = zx_pwm_readl(zpc, pwm->hwpwm, ZX_PWM_MODE);
if (value & ZX_PWM_POLAR)
state->polarity = PWM_POLARITY_NORMAL;
else
state->polarity = PWM_POLARITY_INVERSED;
if (value & ZX_PWM_EN)
state->enabled = true;
else
state->enabled = false;
div = (value & ZX_PWM_CLKDIV_MASK) >> ZX_PWM_CLKDIV_SHIFT;
rate = clk_get_rate(zpc->wclk);
tmp = zx_pwm_readl(zpc, pwm->hwpwm, ZX_PWM_PERIOD);
tmp *= div * NSEC_PER_SEC;
state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);
tmp = zx_pwm_readl(zpc, pwm->hwpwm, ZX_PWM_DUTY);
tmp *= div * NSEC_PER_SEC;
state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);
}
static int zx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned int duty_ns, unsigned int period_ns)
{
struct zx_pwm_chip *zpc = to_zx_pwm_chip(chip);
unsigned int period_cycles, duty_cycles;
unsigned long long c;
unsigned int div = 1;
unsigned long rate;
/* Find out the best divider */
rate = clk_get_rate(zpc->wclk);
while (1) {
c = rate / div;
c = c * period_ns;
do_div(c, NSEC_PER_SEC);
if (c < ZX_PWM_PERIOD_MAX)
break;
div++;
if (div > ZX_PWM_CLKDIV_MAX)
return -ERANGE;
}
/* Calculate duty cycles */
period_cycles = c;
c *= duty_ns;
do_div(c, period_ns);
duty_cycles = c;
/*
* If the PWM is being enabled, we have to temporarily disable it
* before configuring the registers.
*/
if (pwm_is_enabled(pwm))
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE, ZX_PWM_EN, 0);
/* Set up registers */
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE, ZX_PWM_CLKDIV_MASK,
ZX_PWM_CLKDIV(div));
zx_pwm_writel(zpc, pwm->hwpwm, ZX_PWM_PERIOD, period_cycles);
zx_pwm_writel(zpc, pwm->hwpwm, ZX_PWM_DUTY, duty_cycles);
/* Re-enable the PWM if needed */
if (pwm_is_enabled(pwm))
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE,
ZX_PWM_EN, ZX_PWM_EN);
return 0;
}
static int zx_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct zx_pwm_chip *zpc = to_zx_pwm_chip(chip);
struct pwm_state cstate;
int ret;
pwm_get_state(pwm, &cstate);
if (state->polarity != cstate.polarity)
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE, ZX_PWM_POLAR,
(state->polarity == PWM_POLARITY_INVERSED) ?
0 : ZX_PWM_POLAR);
if (state->period != cstate.period ||
state->duty_cycle != cstate.duty_cycle) {
ret = zx_pwm_config(chip, pwm, state->duty_cycle,
state->period);
if (ret)
return ret;
}
if (state->enabled != cstate.enabled) {
if (state->enabled) {
ret = clk_prepare_enable(zpc->wclk);
if (ret)
return ret;
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE,
ZX_PWM_EN, ZX_PWM_EN);
} else {
zx_pwm_set_mask(zpc, pwm->hwpwm, ZX_PWM_MODE,
ZX_PWM_EN, 0);
clk_disable_unprepare(zpc->wclk);
}
}
return 0;
}
static const struct pwm_ops zx_pwm_ops = {
.apply = zx_pwm_apply,
.get_state = zx_pwm_get_state,
.owner = THIS_MODULE,
};
static int zx_pwm_probe(struct platform_device *pdev)
{
struct zx_pwm_chip *zpc;
struct resource *res;
unsigned int i;
int ret;
zpc = devm_kzalloc(&pdev->dev, sizeof(*zpc), GFP_KERNEL);
if (!zpc)
return -ENOMEM;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
zpc->base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(zpc->base))
return PTR_ERR(zpc->base);
zpc->pclk = devm_clk_get(&pdev->dev, "pclk");
if (IS_ERR(zpc->pclk))
return PTR_ERR(zpc->pclk);
zpc->wclk = devm_clk_get(&pdev->dev, "wclk");
if (IS_ERR(zpc->wclk))
return PTR_ERR(zpc->wclk);
ret = clk_prepare_enable(zpc->pclk);
if (ret)
return ret;
zpc->chip.dev = &pdev->dev;
zpc->chip.ops = &zx_pwm_ops;
zpc->chip.base = -1;
zpc->chip.npwm = 4;
zpc->chip.of_xlate = of_pwm_xlate_with_flags;
zpc->chip.of_pwm_n_cells = 3;
/*
* PWM devices may be enabled by firmware, and let's disable all of
* them initially to save power.
*/
for (i = 0; i < zpc->chip.npwm; i++)
zx_pwm_set_mask(zpc, i, ZX_PWM_MODE, ZX_PWM_EN, 0);
ret = pwmchip_add(&zpc->chip);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
return ret;
}
platform_set_drvdata(pdev, zpc);
return 0;
}
static int zx_pwm_remove(struct platform_device *pdev)
{
struct zx_pwm_chip *zpc = platform_get_drvdata(pdev);
int ret;
ret = pwmchip_remove(&zpc->chip);
clk_disable_unprepare(zpc->pclk);
return ret;
}
static const struct of_device_id zx_pwm_dt_ids[] = {
{ .compatible = "zte,zx296718-pwm", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, zx_pwm_dt_ids);
static struct platform_driver zx_pwm_driver = {
.driver = {
.name = "zx-pwm",
.of_match_table = zx_pwm_dt_ids,
},
.probe = zx_pwm_probe,
.remove = zx_pwm_remove,
};
module_platform_driver(zx_pwm_driver);
MODULE_ALIAS("platform:zx-pwm");
MODULE_AUTHOR("Shawn Guo <shawn.guo@linaro.org>");
MODULE_DESCRIPTION("ZTE ZX PWM Driver");
MODULE_LICENSE("GPL v2");
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