Contributors: 43
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Enric Balletbò i Serra |
726 |
25.46% |
5 |
6.41% |
| Thierry Reding |
495 |
17.36% |
7 |
8.97% |
| Eric Miao |
431 |
15.11% |
2 |
2.56% |
| Philipp Zabel |
184 |
6.45% |
3 |
3.85% |
| Matthias Kaehlcke |
178 |
6.24% |
4 |
5.13% |
| Uwe Kleine-König |
114 |
4.00% |
4 |
5.13% |
| Ben Dooks |
101 |
3.54% |
4 |
5.13% |
| Alexandru M Stan |
89 |
3.12% |
1 |
1.28% |
| Peter Ujfalusi |
79 |
2.77% |
3 |
3.85% |
| Heiko Stübner |
50 |
1.75% |
2 |
2.56% |
| Alexander Stein |
46 |
1.61% |
1 |
1.28% |
| Daniel R Thompson |
42 |
1.47% |
2 |
2.56% |
| Huayi Li |
30 |
1.05% |
1 |
1.28% |
| Rasmus Villemoes |
30 |
1.05% |
4 |
5.13% |
| Dilan Lee |
30 |
1.05% |
1 |
1.28% |
| Alexandre Courbot |
29 |
1.02% |
3 |
3.85% |
| Mike Dunn |
29 |
1.02% |
1 |
1.28% |
| Arun Murthy |
26 |
0.91% |
1 |
1.28% |
| Matthew Garrett |
19 |
0.67% |
2 |
2.56% |
| Marc Zyngier |
17 |
0.60% |
1 |
1.28% |
| Christophe Jaillet |
17 |
0.60% |
1 |
1.28% |
| Mark Brown |
16 |
0.56% |
1 |
1.28% |
| Julia Lawall |
11 |
0.39% |
1 |
1.28% |
| Derek Basehore |
11 |
0.39% |
1 |
1.28% |
| Jingoo Han |
11 |
0.39% |
3 |
3.85% |
| Jonathan Woithe |
6 |
0.21% |
1 |
1.28% |
| Sean Young |
6 |
0.21% |
1 |
1.28% |
| Guru Das Srinagesh |
4 |
0.14% |
1 |
1.28% |
| Vladimir Zapolskiy |
4 |
0.14% |
1 |
1.28% |
| Sam Ravnborg |
3 |
0.11% |
1 |
1.28% |
| Maxime Ripard |
2 |
0.07% |
1 |
1.28% |
| Axel Lin |
2 |
0.07% |
2 |
2.56% |
| Robert Morell |
2 |
0.07% |
1 |
1.28% |
| Linus Torvalds (pre-git) |
2 |
0.07% |
1 |
1.28% |
| Andy Shevchenko |
2 |
0.07% |
1 |
1.28% |
| Linus Torvalds |
1 |
0.04% |
1 |
1.28% |
| Alexandre Belloni |
1 |
0.04% |
1 |
1.28% |
| Boris Brezillon |
1 |
0.04% |
1 |
1.28% |
| Chen-Yu Tsai |
1 |
0.04% |
1 |
1.28% |
| Thomas Gleixner |
1 |
0.04% |
1 |
1.28% |
| Emese Revfy |
1 |
0.04% |
1 |
1.28% |
| Sachin Kamat |
1 |
0.04% |
1 |
1.28% |
| Arvind Yadav |
1 |
0.04% |
1 |
1.28% |
| Total |
2852 |
|
78 |
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Simple PWM based backlight control, board code has to setup
* 1) pin configuration so PWM waveforms can output
* 2) platform_data being correctly configured
*/
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>
struct pwm_bl_data {
struct pwm_device *pwm;
struct device *dev;
unsigned int lth_brightness;
unsigned int *levels;
bool enabled;
struct regulator *power_supply;
struct gpio_desc *enable_gpio;
unsigned int scale;
unsigned int post_pwm_on_delay;
unsigned int pwm_off_delay;
int (*notify)(struct device *,
int brightness);
void (*notify_after)(struct device *,
int brightness);
void (*exit)(struct device *);
};
static void pwm_backlight_power_on(struct pwm_bl_data *pb)
{
int err;
if (pb->enabled)
return;
if (pb->power_supply) {
err = regulator_enable(pb->power_supply);
if (err < 0)
dev_err(pb->dev, "failed to enable power supply\n");
}
if (pb->post_pwm_on_delay)
msleep(pb->post_pwm_on_delay);
gpiod_set_value_cansleep(pb->enable_gpio, 1);
pb->enabled = true;
}
static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
if (!pb->enabled)
return;
gpiod_set_value_cansleep(pb->enable_gpio, 0);
if (pb->pwm_off_delay)
msleep(pb->pwm_off_delay);
if (pb->power_supply)
regulator_disable(pb->power_supply);
pb->enabled = false;
}
static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness, struct pwm_state *state)
{
unsigned int lth = pb->lth_brightness;
u64 duty_cycle;
if (pb->levels)
duty_cycle = pb->levels[brightness];
else
duty_cycle = brightness;
duty_cycle *= state->period - lth;
do_div(duty_cycle, pb->scale);
return duty_cycle + lth;
}
static int pwm_backlight_update_status(struct backlight_device *bl)
{
struct pwm_bl_data *pb = bl_get_data(bl);
int brightness = backlight_get_brightness(bl);
struct pwm_state state;
if (pb->notify)
brightness = pb->notify(pb->dev, brightness);
if (brightness > 0) {
pwm_get_state(pb->pwm, &state);
state.duty_cycle = compute_duty_cycle(pb, brightness, &state);
state.enabled = true;
pwm_apply_might_sleep(pb->pwm, &state);
pwm_backlight_power_on(pb);
} else {
pwm_backlight_power_off(pb);
pwm_get_state(pb->pwm, &state);
state.duty_cycle = 0;
/*
* We cannot assume a disabled PWM to drive its output to the
* inactive state. If we have an enable GPIO and/or a regulator
* we assume that this isn't relevant and we can disable the PWM
* to save power. If however there is neither an enable GPIO nor
* a regulator keep the PWM on be sure to get a constant
* inactive output.
*/
state.enabled = !pb->power_supply && !pb->enable_gpio;
pwm_apply_might_sleep(pb->pwm, &state);
}
if (pb->notify_after)
pb->notify_after(pb->dev, brightness);
return 0;
}
static const struct backlight_ops pwm_backlight_ops = {
.update_status = pwm_backlight_update_status,
};
#ifdef CONFIG_OF
#define PWM_LUMINANCE_SHIFT 16
#define PWM_LUMINANCE_SCALE (1 << PWM_LUMINANCE_SHIFT) /* luminance scale */
/*
* CIE lightness to PWM conversion.
*
* The CIE 1931 lightness formula is what actually describes how we perceive
* light:
* Y = (L* / 903.3) if L* ≤ 8
* Y = ((L* + 16) / 116)^3 if L* > 8
*
* Where Y is the luminance, the amount of light coming out of the screen, and
* is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
* perceives the screen to be, and is a number between 0 and 100.
*
* The following function does the fixed point maths needed to implement the
* above formula.
*/
static u64 cie1931(unsigned int lightness)
{
u64 retval;
/*
* @lightness is given as a number between 0 and 1, expressed
* as a fixed-point number in scale
* PWM_LUMINANCE_SCALE. Convert to a percentage, still
* expressed as a fixed-point number, so the above formulas
* can be applied.
*/
lightness *= 100;
if (lightness <= (8 * PWM_LUMINANCE_SCALE)) {
retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
} else {
retval = (lightness + (16 * PWM_LUMINANCE_SCALE)) / 116;
retval *= retval * retval;
retval += 1ULL << (2*PWM_LUMINANCE_SHIFT - 1);
retval >>= 2*PWM_LUMINANCE_SHIFT;
}
return retval;
}
/*
* Create a default correction table for PWM values to create linear brightness
* for LED based backlights using the CIE1931 algorithm.
*/
static
int pwm_backlight_brightness_default(struct device *dev,
struct platform_pwm_backlight_data *data,
unsigned int period)
{
unsigned int i;
u64 retval;
/*
* Once we have 4096 levels there's little point going much higher...
* neither interactive sliders nor animation benefits from having
* more values in the table.
*/
data->max_brightness =
min((int)DIV_ROUND_UP(period, fls(period)), 4096);
data->levels = devm_kcalloc(dev, data->max_brightness,
sizeof(*data->levels), GFP_KERNEL);
if (!data->levels)
return -ENOMEM;
/* Fill the table using the cie1931 algorithm */
for (i = 0; i < data->max_brightness; i++) {
retval = cie1931((i * PWM_LUMINANCE_SCALE) /
data->max_brightness) * period;
retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
if (retval > UINT_MAX)
return -EINVAL;
data->levels[i] = (unsigned int)retval;
}
data->dft_brightness = data->max_brightness / 2;
data->max_brightness--;
return 0;
}
static int pwm_backlight_parse_dt(struct device *dev,
struct platform_pwm_backlight_data *data)
{
struct device_node *node = dev->of_node;
unsigned int num_levels;
unsigned int num_steps = 0;
struct property *prop;
unsigned int *table;
int length;
u32 value;
int ret;
if (!node)
return -ENODEV;
memset(data, 0, sizeof(*data));
/*
* These values are optional and set as 0 by default, the out values
* are modified only if a valid u32 value can be decoded.
*/
of_property_read_u32(node, "post-pwm-on-delay-ms",
&data->post_pwm_on_delay);
of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);
/*
* Determine the number of brightness levels, if this property is not
* set a default table of brightness levels will be used.
*/
prop = of_find_property(node, "brightness-levels", &length);
if (!prop)
return 0;
num_levels = length / sizeof(u32);
/* read brightness levels from DT property */
if (num_levels > 0) {
data->levels = devm_kcalloc(dev, num_levels,
sizeof(*data->levels), GFP_KERNEL);
if (!data->levels)
return -ENOMEM;
ret = of_property_read_u32_array(node, "brightness-levels",
data->levels,
num_levels);
if (ret < 0)
return ret;
ret = of_property_read_u32(node, "default-brightness-level",
&value);
if (ret < 0)
return ret;
data->dft_brightness = value;
/*
* This property is optional, if is set enables linear
* interpolation between each of the values of brightness levels
* and creates a new pre-computed table.
*/
of_property_read_u32(node, "num-interpolated-steps",
&num_steps);
/*
* Make sure that there is at least two entries in the
* brightness-levels table, otherwise we can't interpolate
* between two points.
*/
if (num_steps) {
unsigned int num_input_levels = num_levels;
unsigned int i;
u32 x1, x2, x, dx;
u32 y1, y2;
s64 dy;
if (num_input_levels < 2) {
dev_err(dev, "can't interpolate\n");
return -EINVAL;
}
/*
* Recalculate the number of brightness levels, now
* taking in consideration the number of interpolated
* steps between two levels.
*/
num_levels = (num_input_levels - 1) * num_steps + 1;
dev_dbg(dev, "new number of brightness levels: %d\n",
num_levels);
/*
* Create a new table of brightness levels with all the
* interpolated steps.
*/
table = devm_kcalloc(dev, num_levels, sizeof(*table),
GFP_KERNEL);
if (!table)
return -ENOMEM;
/*
* Fill the interpolated table[x] = y
* by draw lines between each (x1, y1) to (x2, y2).
*/
dx = num_steps;
for (i = 0; i < num_input_levels - 1; i++) {
x1 = i * dx;
x2 = x1 + dx;
y1 = data->levels[i];
y2 = data->levels[i + 1];
dy = (s64)y2 - y1;
for (x = x1; x < x2; x++) {
table[x] = y1 +
div_s64(dy * (x - x1), dx);
}
}
/* Fill in the last point, since no line starts here. */
table[x2] = y2;
/*
* As we use interpolation lets remove current
* brightness levels table and replace for the
* new interpolated table.
*/
devm_kfree(dev, data->levels);
data->levels = table;
}
data->max_brightness = num_levels - 1;
}
return 0;
}
static const struct of_device_id pwm_backlight_of_match[] = {
{ .compatible = "pwm-backlight" },
{ }
};
MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
#else
static int pwm_backlight_parse_dt(struct device *dev,
struct platform_pwm_backlight_data *data)
{
return -ENODEV;
}
static
int pwm_backlight_brightness_default(struct device *dev,
struct platform_pwm_backlight_data *data,
unsigned int period)
{
return -ENODEV;
}
#endif
static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
{
unsigned int nlevels = data->max_brightness + 1;
unsigned int min_val = data->levels[0];
unsigned int max_val = data->levels[nlevels - 1];
/*
* Multiplying by 128 means that even in pathological cases such
* as (max_val - min_val) == nlevels the error at max_val is less
* than 1%.
*/
unsigned int slope = (128 * (max_val - min_val)) / nlevels;
unsigned int margin = (max_val - min_val) / 20; /* 5% */
int i;
for (i = 1; i < nlevels; i++) {
unsigned int linear_value = min_val + ((i * slope) / 128);
unsigned int delta = abs(linear_value - data->levels[i]);
if (delta > margin)
return false;
}
return true;
}
static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
{
struct device_node *node = pb->dev->of_node;
bool active = true;
/*
* If the enable GPIO is present, observable (either as input
* or output) and off then the backlight is not currently active.
* */
if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
active = false;
if (pb->power_supply && !regulator_is_enabled(pb->power_supply))
active = false;
if (!pwm_is_enabled(pb->pwm))
active = false;
/*
* Synchronize the enable_gpio with the observed state of the
* hardware.
*/
gpiod_direction_output(pb->enable_gpio, active);
/*
* Do not change pb->enabled here! pb->enabled essentially
* tells us if we own one of the regulator's use counts and
* right now we do not.
*/
/* Not booted with device tree or no phandle link to the node */
if (!node || !node->phandle)
return FB_BLANK_UNBLANK;
/*
* If the driver is probed from the device tree and there is a
* phandle link pointing to the backlight node, it is safe to
* assume that another driver will enable the backlight at the
* appropriate time. Therefore, if it is disabled, keep it so.
*/
return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN;
}
static int pwm_backlight_probe(struct platform_device *pdev)
{
struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
struct platform_pwm_backlight_data defdata;
struct backlight_properties props;
struct backlight_device *bl;
struct pwm_bl_data *pb;
struct pwm_state state;
unsigned int i;
int ret;
if (!data) {
ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
if (ret < 0)
return dev_err_probe(&pdev->dev, ret,
"failed to find platform data\n");
data = &defdata;
}
if (data->init) {
ret = data->init(&pdev->dev);
if (ret < 0)
return ret;
}
pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
if (!pb) {
ret = -ENOMEM;
goto err_alloc;
}
pb->notify = data->notify;
pb->notify_after = data->notify_after;
pb->exit = data->exit;
pb->dev = &pdev->dev;
pb->enabled = false;
pb->post_pwm_on_delay = data->post_pwm_on_delay;
pb->pwm_off_delay = data->pwm_off_delay;
pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
GPIOD_ASIS);
if (IS_ERR(pb->enable_gpio)) {
ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->enable_gpio),
"failed to acquire enable GPIO\n");
goto err_alloc;
}
pb->power_supply = devm_regulator_get_optional(&pdev->dev, "power");
if (IS_ERR(pb->power_supply)) {
ret = PTR_ERR(pb->power_supply);
if (ret == -ENODEV) {
pb->power_supply = NULL;
} else {
dev_err_probe(&pdev->dev, ret,
"failed to acquire power regulator\n");
goto err_alloc;
}
}
pb->pwm = devm_pwm_get(&pdev->dev, NULL);
if (IS_ERR(pb->pwm)) {
ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->pwm),
"unable to request PWM\n");
goto err_alloc;
}
dev_dbg(&pdev->dev, "got pwm for backlight\n");
/* Sync up PWM state. */
pwm_init_state(pb->pwm, &state);
/*
* The DT case will set the pwm_period_ns field to 0 and store the
* period, parsed from the DT, in the PWM device. For the non-DT case,
* set the period from platform data if it has not already been set
* via the PWM lookup table.
*/
if (!state.period && (data->pwm_period_ns > 0))
state.period = data->pwm_period_ns;
ret = pwm_apply_might_sleep(pb->pwm, &state);
if (ret) {
dev_err_probe(&pdev->dev, ret,
"failed to apply initial PWM state");
goto err_alloc;
}
memset(&props, 0, sizeof(struct backlight_properties));
if (data->levels) {
pb->levels = data->levels;
/*
* For the DT case, only when brightness levels is defined
* data->levels is filled. For the non-DT case, data->levels
* can come from platform data, however is not usual.
*/
for (i = 0; i <= data->max_brightness; i++)
if (data->levels[i] > pb->scale)
pb->scale = data->levels[i];
if (pwm_backlight_is_linear(data))
props.scale = BACKLIGHT_SCALE_LINEAR;
else
props.scale = BACKLIGHT_SCALE_NON_LINEAR;
} else if (!data->max_brightness) {
/*
* If no brightness levels are provided and max_brightness is
* not set, use the default brightness table. For the DT case,
* max_brightness is set to 0 when brightness levels is not
* specified. For the non-DT case, max_brightness is usually
* set to some value.
*/
/* Get the PWM period (in nanoseconds) */
pwm_get_state(pb->pwm, &state);
ret = pwm_backlight_brightness_default(&pdev->dev, data,
state.period);
if (ret < 0) {
dev_err_probe(&pdev->dev, ret,
"failed to setup default brightness table\n");
goto err_alloc;
}
for (i = 0; i <= data->max_brightness; i++) {
if (data->levels[i] > pb->scale)
pb->scale = data->levels[i];
pb->levels = data->levels;
}
props.scale = BACKLIGHT_SCALE_NON_LINEAR;
} else {
/*
* That only happens for the non-DT case, where platform data
* sets the max_brightness value.
*/
pb->scale = data->max_brightness;
}
pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
pb->scale));
props.type = BACKLIGHT_RAW;
props.max_brightness = data->max_brightness;
bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
&pwm_backlight_ops, &props);
if (IS_ERR(bl)) {
ret = dev_err_probe(&pdev->dev, PTR_ERR(bl),
"failed to register backlight\n");
goto err_alloc;
}
if (data->dft_brightness > data->max_brightness) {
dev_warn(&pdev->dev,
"invalid default brightness level: %u, using %u\n",
data->dft_brightness, data->max_brightness);
data->dft_brightness = data->max_brightness;
}
bl->props.brightness = data->dft_brightness;
bl->props.power = pwm_backlight_initial_power_state(pb);
backlight_update_status(bl);
platform_set_drvdata(pdev, bl);
return 0;
err_alloc:
if (data->exit)
data->exit(&pdev->dev);
return ret;
}
static void pwm_backlight_remove(struct platform_device *pdev)
{
struct backlight_device *bl = platform_get_drvdata(pdev);
struct pwm_bl_data *pb = bl_get_data(bl);
struct pwm_state state;
backlight_device_unregister(bl);
pwm_backlight_power_off(pb);
pwm_get_state(pb->pwm, &state);
state.duty_cycle = 0;
state.enabled = false;
pwm_apply_might_sleep(pb->pwm, &state);
if (pb->exit)
pb->exit(&pdev->dev);
}
static void pwm_backlight_shutdown(struct platform_device *pdev)
{
struct backlight_device *bl = platform_get_drvdata(pdev);
struct pwm_bl_data *pb = bl_get_data(bl);
struct pwm_state state;
pwm_backlight_power_off(pb);
pwm_get_state(pb->pwm, &state);
state.duty_cycle = 0;
state.enabled = false;
pwm_apply_might_sleep(pb->pwm, &state);
}
#ifdef CONFIG_PM_SLEEP
static int pwm_backlight_suspend(struct device *dev)
{
struct backlight_device *bl = dev_get_drvdata(dev);
struct pwm_bl_data *pb = bl_get_data(bl);
struct pwm_state state;
if (pb->notify)
pb->notify(pb->dev, 0);
pwm_backlight_power_off(pb);
/*
* Note that disabling the PWM doesn't guarantee that the output stays
* at its inactive state. However without the PWM disabled, the PWM
* driver refuses to suspend. So disable here even though this might
* enable the backlight on poorly designed boards.
*/
pwm_get_state(pb->pwm, &state);
state.duty_cycle = 0;
state.enabled = false;
pwm_apply_might_sleep(pb->pwm, &state);
if (pb->notify_after)
pb->notify_after(pb->dev, 0);
return 0;
}
static int pwm_backlight_resume(struct device *dev)
{
struct backlight_device *bl = dev_get_drvdata(dev);
backlight_update_status(bl);
return 0;
}
#endif
static const struct dev_pm_ops pwm_backlight_pm_ops = {
#ifdef CONFIG_PM_SLEEP
.suspend = pwm_backlight_suspend,
.resume = pwm_backlight_resume,
.poweroff = pwm_backlight_suspend,
.restore = pwm_backlight_resume,
#endif
};
static struct platform_driver pwm_backlight_driver = {
.driver = {
.name = "pwm-backlight",
.pm = &pwm_backlight_pm_ops,
.of_match_table = of_match_ptr(pwm_backlight_of_match),
},
.probe = pwm_backlight_probe,
.remove_new = pwm_backlight_remove,
.shutdown = pwm_backlight_shutdown,
};
module_platform_driver(pwm_backlight_driver);
MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:pwm-backlight");