| // 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/gpio.h> |
| #include <linux/module.h> |
| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/platform_device.h> |
| #include <linux/fb.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; |
| bool legacy; |
| unsigned int post_pwm_on_delay; |
| unsigned int pwm_off_delay; |
| int (*notify)(struct device *, |
| int brightness); |
| void (*notify_after)(struct device *, |
| int brightness); |
| int (*check_fb)(struct device *, struct fb_info *); |
| void (*exit)(struct device *); |
| }; |
| |
| static void pwm_backlight_power_on(struct pwm_bl_data *pb) |
| { |
| struct pwm_state state; |
| int err; |
| |
| pwm_get_state(pb->pwm, &state); |
| if (pb->enabled) |
| return; |
| |
| err = regulator_enable(pb->power_supply); |
| if (err < 0) |
| dev_err(pb->dev, "failed to enable power supply\n"); |
| |
| state.enabled = true; |
| pwm_apply_state(pb->pwm, &state); |
| |
| if (pb->post_pwm_on_delay) |
| msleep(pb->post_pwm_on_delay); |
| |
| if (pb->enable_gpio) |
| gpiod_set_value_cansleep(pb->enable_gpio, 1); |
| |
| pb->enabled = true; |
| } |
| |
| static void pwm_backlight_power_off(struct pwm_bl_data *pb) |
| { |
| struct pwm_state state; |
| |
| pwm_get_state(pb->pwm, &state); |
| if (!pb->enabled) |
| return; |
| |
| if (pb->enable_gpio) |
| gpiod_set_value_cansleep(pb->enable_gpio, 0); |
| |
| if (pb->pwm_off_delay) |
| msleep(pb->pwm_off_delay); |
| |
| state.enabled = false; |
| state.duty_cycle = 0; |
| pwm_apply_state(pb->pwm, &state); |
| |
| regulator_disable(pb->power_supply); |
| pb->enabled = false; |
| } |
| |
| static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) |
| { |
| unsigned int lth = pb->lth_brightness; |
| struct pwm_state state; |
| u64 duty_cycle; |
| |
| pwm_get_state(pb->pwm, &state); |
| |
| 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 = bl->props.brightness; |
| struct pwm_state state; |
| |
| if (bl->props.power != FB_BLANK_UNBLANK || |
| bl->props.fb_blank != FB_BLANK_UNBLANK || |
| bl->props.state & BL_CORE_FBBLANK) |
| brightness = 0; |
| |
| 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); |
| pwm_apply_state(pb->pwm, &state); |
| pwm_backlight_power_on(pb); |
| } else |
| pwm_backlight_power_off(pb); |
| |
| if (pb->notify_after) |
| pb->notify_after(pb->dev, brightness); |
| |
| return 0; |
| } |
| |
| static int pwm_backlight_check_fb(struct backlight_device *bl, |
| struct fb_info *info) |
| { |
| struct pwm_bl_data *pb = bl_get_data(bl); |
| |
| return !pb->check_fb || pb->check_fb(pb->dev, info); |
| } |
| |
| static const struct backlight_ops pwm_backlight_ops = { |
| .update_status = pwm_backlight_update_status, |
| .check_fb = pwm_backlight_check_fb, |
| }; |
| |
| #ifdef CONFIG_OF |
| #define PWM_LUMINANCE_SCALE 10000 /* luminance scale */ |
| |
| /* |
| * CIE lightness to PWM conversion. |
| * |
| * The CIE 1931 lightness formula is what actually describes how we perceive |
| * light: |
| * Y = (L* / 902.3) if L* ≤ 0.08856 |
| * Y = ((L* + 16) / 116)^3 if L* > 0.08856 |
| * |
| * 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, unsigned int scale) |
| { |
| u64 retval; |
| |
| lightness *= 100; |
| if (lightness <= (8 * scale)) { |
| retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9023); |
| } else { |
| retval = int_pow((lightness + (16 * scale)) / 116, 3); |
| retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale)); |
| } |
| |
| 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, PWM_LUMINANCE_SCALE) * |
| 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 = 0; |
| unsigned int levels_count; |
| 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); |
| |
| data->enable_gpio = -EINVAL; |
| |
| /* |
| * 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; |
| |
| data->max_brightness = length / sizeof(u32); |
| |
| /* read brightness levels from DT property */ |
| if (data->max_brightness > 0) { |
| size_t size = sizeof(*data->levels) * data->max_brightness; |
| unsigned int i, j, n = 0; |
| |
| data->levels = devm_kzalloc(dev, size, GFP_KERNEL); |
| if (!data->levels) |
| return -ENOMEM; |
| |
| ret = of_property_read_u32_array(node, "brightness-levels", |
| data->levels, |
| data->max_brightness); |
| 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) { |
| if (data->max_brightness < 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. |
| */ |
| for (i = 0; i < data->max_brightness - 1; i++) { |
| if ((data->levels[i + 1] - data->levels[i]) / |
| num_steps) |
| num_levels += num_steps; |
| else |
| num_levels++; |
| } |
| num_levels++; |
| dev_dbg(dev, "new number of brightness levels: %d\n", |
| num_levels); |
| |
| /* |
| * Create a new table of brightness levels with all the |
| * interpolated steps. |
| */ |
| size = sizeof(*table) * num_levels; |
| table = devm_kzalloc(dev, size, GFP_KERNEL); |
| if (!table) |
| return -ENOMEM; |
| |
| /* Fill the interpolated table. */ |
| levels_count = 0; |
| for (i = 0; i < data->max_brightness - 1; i++) { |
| value = data->levels[i]; |
| n = (data->levels[i + 1] - value) / num_steps; |
| if (n > 0) { |
| for (j = 0; j < num_steps; j++) { |
| table[levels_count] = value; |
| value += n; |
| levels_count++; |
| } |
| } else { |
| table[levels_count] = data->levels[i]; |
| levels_count++; |
| } |
| } |
| table[levels_count] = data->levels[i]; |
| |
| /* |
| * 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; |
| |
| /* |
| * Reassign max_brightness value to the new total number |
| * of brightness levels. |
| */ |
| data->max_brightness = num_levels; |
| } |
| |
| data->max_brightness--; |
| } |
| |
| 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 int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) |
| { |
| struct device_node *node = pb->dev->of_node; |
| |
| /* 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. |
| */ |
| |
| /* if the enable GPIO is disabled, do not enable the backlight */ |
| if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0) |
| return FB_BLANK_POWERDOWN; |
| |
| /* The regulator is disabled, do not enable the backlight */ |
| if (!regulator_is_enabled(pb->power_supply)) |
| return FB_BLANK_POWERDOWN; |
| |
| /* The PWM is disabled, keep it like this */ |
| if (!pwm_is_enabled(pb->pwm)) |
| return FB_BLANK_POWERDOWN; |
| |
| return FB_BLANK_UNBLANK; |
| } |
| |
| 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 device_node *node = pdev->dev.of_node; |
| 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) { |
| dev_err(&pdev->dev, "failed to find platform data\n"); |
| return ret; |
| } |
| |
| 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->check_fb = data->check_fb; |
| 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 = PTR_ERR(pb->enable_gpio); |
| goto err_alloc; |
| } |
| |
| /* |
| * Compatibility fallback for drivers still using the integer GPIO |
| * platform data. Must go away soon. |
| */ |
| if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { |
| ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, |
| GPIOF_OUT_INIT_HIGH, "enable"); |
| if (ret < 0) { |
| dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", |
| data->enable_gpio, ret); |
| goto err_alloc; |
| } |
| |
| pb->enable_gpio = gpio_to_desc(data->enable_gpio); |
| } |
| |
| /* |
| * If the GPIO is not known to be already configured as output, that |
| * is, if gpiod_get_direction returns either 1 or -EINVAL, change the |
| * direction to output and set the GPIO as active. |
| * Do not force the GPIO to active when it was already output as it |
| * could cause backlight flickering or we would enable the backlight too |
| * early. Leave the decision of the initial backlight state for later. |
| */ |
| if (pb->enable_gpio && |
| gpiod_get_direction(pb->enable_gpio) != 0) |
| gpiod_direction_output(pb->enable_gpio, 1); |
| |
| pb->power_supply = devm_regulator_get(&pdev->dev, "power"); |
| if (IS_ERR(pb->power_supply)) { |
| ret = PTR_ERR(pb->power_supply); |
| goto err_alloc; |
| } |
| |
| pb->pwm = devm_pwm_get(&pdev->dev, NULL); |
| if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) { |
| dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); |
| pb->legacy = true; |
| pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); |
| } |
| |
| if (IS_ERR(pb->pwm)) { |
| ret = PTR_ERR(pb->pwm); |
| if (ret != -EPROBE_DEFER) |
| dev_err(&pdev->dev, "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_state(pb->pwm, &state); |
| if (ret) { |
| dev_err(&pdev->dev, "failed to apply initial PWM state: %d\n", |
| ret); |
| goto err_alloc; |
| } |
| |
| if (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]; |
| |
| pb->levels = data->levels; |
| } |
| } 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(&pdev->dev, |
| "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; |
| } |
| } 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 * (state.period / pb->scale); |
| |
| memset(&props, 0, sizeof(struct backlight_properties)); |
| 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)) { |
| dev_err(&pdev->dev, "failed to register backlight\n"); |
| ret = PTR_ERR(bl); |
| if (pb->legacy) |
| pwm_free(pb->pwm); |
| 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 int pwm_backlight_remove(struct platform_device *pdev) |
| { |
| struct backlight_device *bl = platform_get_drvdata(pdev); |
| struct pwm_bl_data *pb = bl_get_data(bl); |
| |
| backlight_device_unregister(bl); |
| pwm_backlight_power_off(pb); |
| |
| if (pb->exit) |
| pb->exit(&pdev->dev); |
| if (pb->legacy) |
| pwm_free(pb->pwm); |
| |
| return 0; |
| } |
| |
| 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); |
| |
| pwm_backlight_power_off(pb); |
| } |
| |
| #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); |
| |
| if (pb->notify) |
| pb->notify(pb->dev, 0); |
| |
| pwm_backlight_power_off(pb); |
| |
| 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 = 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"); |