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alistair23-linux/drivers/pwm/pwm-lpss.c
Hans de Goede 1d375b58c1 pwm: lpss: platform: Save/restore the ctrl register over a suspend/resume 
On some devices the contents of the ctrl register get lost over a
suspend/resume and the PWM comes back up disabled after the resume.

This is seen on some Bay Trail devices with the PWM in ACPI enumerated
mode, so it shows up as a platform device instead of a PCI device.

If we still think it is enabled and then try to change the duty-cycle
after this, we end up with a "PWM_SW_UPDATE was not cleared" error and
the PWM is stuck in that state from then on.

This commit adds suspend and resume pm callbacks to the pwm-lpss-platform
code, which save/restore the ctrl register over a suspend/resume, fixing
this.

Note that:

1) There is no need to do this over a runtime suspend, since we
only runtime suspend when disabled and then we properly set the enable
bit and reprogram the timings when we re-enable the PWM.

2) This may be happening on more systems then we realize, but has been
covered up sofar by a bug in the acpi-lpss.c code which was save/restoring
the regular device registers instead of the lpss private registers due to
lpss_device_desc.prv_offset not being set. This is fixed by a later patch
in this series.

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2018-06-06 10:00:39 +02:00

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6.4 KiB
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/*
* Intel Low Power Subsystem PWM controller driver
*
* Copyright (C) 2014, Intel Corporation
* Author: Mika Westerberg <mika.westerberg@linux.intel.com>
* Author: Chew Kean Ho <kean.ho.chew@intel.com>
* Author: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
* Author: Chew Chiau Ee <chiau.ee.chew@intel.com>
* Author: Alan Cox <alan@linux.intel.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/time.h>
#include "pwm-lpss.h"
#define PWM 0x00000000
#define PWM_ENABLE BIT(31)
#define PWM_SW_UPDATE BIT(30)
#define PWM_BASE_UNIT_SHIFT 8
#define PWM_ON_TIME_DIV_MASK 0x000000ff
/* Size of each PWM register space if multiple */
#define PWM_SIZE 0x400
#define MAX_PWMS 4
struct pwm_lpss_chip {
struct pwm_chip chip;
void __iomem *regs;
const struct pwm_lpss_boardinfo *info;
u32 saved_ctrl[MAX_PWMS];
};
static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
{
return container_of(chip, struct pwm_lpss_chip, chip);
}
static inline u32 pwm_lpss_read(const struct pwm_device *pwm)
{
struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
return readl(lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
}
static inline void pwm_lpss_write(const struct pwm_device *pwm, u32 value)
{
struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
writel(value, lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
}
static int pwm_lpss_wait_for_update(struct pwm_device *pwm)
{
struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
const void __iomem *addr = lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM;
const unsigned int ms = 500 * USEC_PER_MSEC;
u32 val;
int err;
/*
* PWM Configuration register has SW_UPDATE bit that is set when a new
* configuration is written to the register. The bit is automatically
* cleared at the start of the next output cycle by the IP block.
*
* If one writes a new configuration to the register while it still has
* the bit enabled, PWM may freeze. That is, while one can still write
* to the register, it won't have an effect. Thus, we try to sleep long
* enough that the bit gets cleared and make sure the bit is not
* enabled while we update the configuration.
*/
err = readl_poll_timeout(addr, val, !(val & PWM_SW_UPDATE), 40, ms);
if (err)
dev_err(pwm->chip->dev, "PWM_SW_UPDATE was not cleared\n");
return err;
}
static inline int pwm_lpss_is_updating(struct pwm_device *pwm)
{
return (pwm_lpss_read(pwm) & PWM_SW_UPDATE) ? -EBUSY : 0;
}
static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
unsigned long long on_time_div;
unsigned long c = lpwm->info->clk_rate, base_unit_range;
unsigned long long base_unit, freq = NSEC_PER_SEC;
u32 ctrl;
do_div(freq, period_ns);
/*
* The equation is:
* base_unit = round(base_unit_range * freq / c)
*/
base_unit_range = BIT(lpwm->info->base_unit_bits) - 1;
freq *= base_unit_range;
base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
on_time_div = 255ULL * duty_ns;
do_div(on_time_div, period_ns);
on_time_div = 255ULL - on_time_div;
ctrl = pwm_lpss_read(pwm);
ctrl &= ~PWM_ON_TIME_DIV_MASK;
ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT);
base_unit &= base_unit_range;
ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
ctrl |= on_time_div;
pwm_lpss_write(pwm, ctrl);
}
static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
{
if (cond)
pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
}
static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct pwm_lpss_chip *lpwm = to_lpwm(chip);
int ret;
if (state->enabled) {
if (!pwm_is_enabled(pwm)) {
pm_runtime_get_sync(chip->dev);
ret = pwm_lpss_is_updating(pwm);
if (ret) {
pm_runtime_put(chip->dev);
return ret;
}
pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
ret = pwm_lpss_wait_for_update(pwm);
if (ret) {
pm_runtime_put(chip->dev);
return ret;
}
pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
} else {
ret = pwm_lpss_is_updating(pwm);
if (ret)
return ret;
pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
return pwm_lpss_wait_for_update(pwm);
}
} else if (pwm_is_enabled(pwm)) {
pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
pm_runtime_put(chip->dev);
}
return 0;
}
static const struct pwm_ops pwm_lpss_ops = {
.apply = pwm_lpss_apply,
.owner = THIS_MODULE,
};
struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
const struct pwm_lpss_boardinfo *info)
{
struct pwm_lpss_chip *lpwm;
unsigned long c;
int ret;
if (WARN_ON(info->npwm > MAX_PWMS))
return ERR_PTR(-ENODEV);
lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
if (!lpwm)
return ERR_PTR(-ENOMEM);
lpwm->regs = devm_ioremap_resource(dev, r);
if (IS_ERR(lpwm->regs))
return ERR_CAST(lpwm->regs);
lpwm->info = info;
c = lpwm->info->clk_rate;
if (!c)
return ERR_PTR(-EINVAL);
lpwm->chip.dev = dev;
lpwm->chip.ops = &pwm_lpss_ops;
lpwm->chip.base = -1;
lpwm->chip.npwm = info->npwm;
ret = pwmchip_add(&lpwm->chip);
if (ret) {
dev_err(dev, "failed to add PWM chip: %d\n", ret);
return ERR_PTR(ret);
}
return lpwm;
}
EXPORT_SYMBOL_GPL(pwm_lpss_probe);
int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
{
return pwmchip_remove(&lpwm->chip);
}
EXPORT_SYMBOL_GPL(pwm_lpss_remove);
int pwm_lpss_suspend(struct device *dev)
{
struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
int i;
for (i = 0; i < lpwm->info->npwm; i++)
lpwm->saved_ctrl[i] = readl(lpwm->regs + i * PWM_SIZE + PWM);
return 0;
}
EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
int pwm_lpss_resume(struct device *dev)
{
struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
int i;
for (i = 0; i < lpwm->info->npwm; i++)
writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
return 0;
}
EXPORT_SYMBOL_GPL(pwm_lpss_resume);
MODULE_DESCRIPTION("PWM driver for Intel LPSS");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
MODULE_LICENSE("GPL v2");
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