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[82.37.195.13]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42abe62b23csm6015125f8f.10.2025.11.07.08.12.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Nov 2025 08:12:21 -0800 (PST) Date: Fri, 7 Nov 2025 16:14:17 +0000 From: Daniel Thompson To: maudspierings@gocontroll.com Cc: Lee Jones , Daniel Thompson , Jingoo Han , Pavel Machek , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Helge Deller , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Liam Girdwood , Mark Brown , dri-devel@lists.freedesktop.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5 2/4] backlight: add max25014atg backlight Message-ID: References: <20251107-max25014-v5-0-9a6aa57306bf@gocontroll.com> <20251107-max25014-v5-2-9a6aa57306bf@gocontroll.com> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251107-max25014-v5-2-9a6aa57306bf@gocontroll.com> On Fri, Nov 07, 2025 at 01:49:59PM +0100, Maud Spierings via B4 Relay wrote: > From: Maud Spierings > > The Maxim MAX25014 is a 4-channel automotive grade backlight driver IC > with integrated boost controller. > > Signed-off-by: Maud Spierings > diff --git a/drivers/video/backlight/max25014.c b/drivers/video/backlight/max25014.c > new file mode 100644 > index 000000000000..36bae508697e > --- /dev/null > +++ b/drivers/video/backlight/max25014.c > @@ -0,0 +1,409 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Backlight driver for Maxim MAX25014 > + * > + * Copyright (C) 2025 GOcontroll B.V. > + * Author: Maud Spierings > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +#define MAX25014_ISET_DEFAULT_100 11 > +#define MAX_BRIGHTNESS 100 > +#define MIN_BRIGHTNESS 0 > +#define TON_MAX 130720 /* @153Hz */ > +#define TON_STEP 1307 /* @153Hz */ > +#define TON_MIN 0 > + > +#define MAX25014_DEV_ID 0x00 > +#define MAX25014_REV_ID 0x01 > +#define MAX25014_ISET 0x02 > +#define MAX25014_IMODE 0x03 > +#define MAX25014_TON1H 0x04 > +#define MAX25014_TON1L 0x05 > +#define MAX25014_TON2H 0x06 > +#define MAX25014_TON2L 0x07 > +#define MAX25014_TON3H 0x08 > +#define MAX25014_TON3L 0x09 > +#define MAX25014_TON4H 0x0A > +#define MAX25014_TON4L 0x0B > +#define MAX25014_TON_1_4_LSB 0x0C > +#define MAX25014_SETTING 0x12 > +#define MAX25014_DISABLE 0x13 > +#define MAX25014_BSTMON 0x14 > +#define MAX25014_IOUT1 0x15 > +#define MAX25014_IOUT2 0x16 > +#define MAX25014_IOUT3 0x17 > +#define MAX25014_IOUT4 0x18 > +#define MAX25014_OPEN 0x1B > +#define MAX25014_SHORT_GND 0x1C > +#define MAX25014_SHORT_LED 0x1D > +#define MAX25014_MASK 0x1E > +#define MAX25014_DIAG 0x1F > + > +#define MAX25014_IMODE_HDIM BIT(2) > +#define MAX25014_ISET_ENABLE BIT(5) > +#define MAX25014_ISET_PSEN BIT(4) > +#define MAX25014_DIAG_HW_RST BIT(2) > +#define MAX25014_SETTING_FPWM GENMASK(6, 4) > + > +struct max25014 { > + struct i2c_client *client; > + struct backlight_device *bl; > + struct regmap *regmap; > + struct gpio_desc *enable; > + struct regulator *vin; /* regulator for boost converter Vin rail */ > + uint32_t iset; > + uint8_t strings_mask; > +}; > + > +static const struct regmap_config max25014_regmap_config = { > + .reg_bits = 8, > + .val_bits = 8, > + .max_register = MAX25014_DIAG, > +}; > + > +/** > + * @brief control the brightness with i2c registers > + * > + * @param regmap trivial > + * @param brt brightness > + * @return int > + */ > +static int max25014_register_control(struct regmap *regmap, uint32_t brt) This isn't a good name for a function. It doesn't really say what it does. Please find a more descriptive name. > +{ > + uint32_t reg = TON_STEP * brt; > + int ret; > + /* > + * 18 bit number lowest, 2 bits in first register, > + * next lowest 8 in the L register, next 8 in the H register > + * Seemingly setting the strength of only one string controls all of > + * them, individual settings don't affect the outcome. > + */ > + > + ret = regmap_write(regmap, MAX25014_TON_1_4_LSB, reg & 0b00000011); > + if (ret != 0) > + return ret; > + ret = regmap_write(regmap, MAX25014_TON1L, (reg >> 2) & 0b11111111); > + if (ret != 0) > + return ret; > + return regmap_write(regmap, MAX25014_TON1H, (reg >> 10) & 0b11111111); > +} > + > +static int max25014_check_errors(struct max25014 *maxim) > +{ > + uint8_t i; > + int ret; > + uint32_t val; > + > + ret = regmap_read(maxim->regmap, MAX25014_OPEN, &val); > + if (ret != 0) > + return ret; > + if (val > 0) { > + dev_err(&maxim->client->dev, "Open led strings detected on:\n"); > + for (i = 0; i < 4; i++) { > + if (val & 1 << i) > + dev_err(&maxim->client->dev, "string %d\n", i + 1); > + } > + return -EIO; > + } > + > + ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val); > + if (ret != 0) > + return ret; > + if (val > 0) { > + dev_err(&maxim->client->dev, "Short to ground detected on:\n"); > + for (i = 0; i < 4; i++) { > + if (val & 1 << i) > + dev_err(&maxim->client->dev, "string %d\n", i + 1); > + } > + return -EIO; > + } > + > + ret = regmap_read(maxim->regmap, MAX25014_SHORT_GND, &val); > + if (ret != 0) > + return ret; > + if (val > 0) { > + dev_err(&maxim->client->dev, "Shorted led detected on:\n"); > + for (i = 0; i < 4; i++) { > + if (val & 1 << i) > + dev_err(&maxim->client->dev, "string %d\n", i + 1); > + } > + return -EIO; > + } > + > + ret = regmap_read(maxim->regmap, MAX25014_DIAG, &val); > + if (ret != 0) > + return ret; > + /* > + * The HW_RST bit always starts at 1 after power up. > + * It is reset on first read, does not indicate an error. > + */ > + if (val > 0 && val != MAX25014_DIAG_HW_RST) { > + if (val & 0b1) > + dev_err(&maxim->client->dev, > + "Overtemperature shutdown\n"); > + if (val & 0b10) > + dev_err(&maxim->client->dev, > + "Chip is getting too hot (>125C)\n"); > + if (val & 0b1000) > + dev_err(&maxim->client->dev, > + "Boost converter overvoltage\n"); > + if (val & 0b10000) > + dev_err(&maxim->client->dev, > + "Boost converter undervoltage\n"); > + if (val & 0b100000) > + dev_err(&maxim->client->dev, "IREF out of range\n"); > + return -EIO; > + } > + return 0; > +} > + > +/* > + * 1. disable unused strings > + * 2. set dim mode > + * 3. set initial brightness How does this code set the initial brightness? It doens't set the MAX25014_TON* registers. > + * 4. set setting register > + * 5. enable the backlight > + */ > +static int max25014_configure(struct max25014 *maxim) > +{ > + int ret; > + uint32_t val; > + > + ret = regmap_write(maxim->regmap, MAX25014_DISABLE, > + maxim->strings_mask); > + if (ret != 0) > + return ret; > + > + ret = regmap_write(maxim->regmap, MAX25014_IMODE, MAX25014_IMODE_HDIM); > + if (ret != 0) > + return ret; > + > + ret = regmap_read(maxim->regmap, MAX25014_SETTING, &val); > + if (ret != 0) > + return ret; > + > + ret = regmap_write(maxim->regmap, MAX25014_SETTING, > + val & ~MAX25014_SETTING_FPWM); > + if (ret != 0) > + return ret; > + > + ret = regmap_write(maxim->regmap, MAX25014_ISET, > + maxim->iset | MAX25014_ISET_ENABLE | > + MAX25014_ISET_PSEN); > + return ret; > +} > + > +static int max25014_update_status(struct backlight_device *bl_dev) > +{ > + struct max25014 *maxim = bl_get_data(bl_dev); > + > + if (backlight_is_blank(maxim->bl)) > + bl_dev->props.brightness = 0; > + > + return max25014_register_control(maxim->regmap, > + bl_dev->props.brightness); > +} > + > +static const struct backlight_ops max25014_bl_ops = { > + .options = BL_CORE_SUSPENDRESUME, > + .update_status = max25014_update_status, > +}; > + > +static int max25014_parse_dt(struct max25014 *maxim, > + uint32_t *initial_brightness) > +{ > + struct device *dev = &maxim->client->dev; > + struct device_node *node = dev->of_node; > + struct fwnode_handle *child; > + uint32_t strings[4]; > + int res, i; > + > + if (!node) { > + dev_err(dev, "no platform data\n"); > + return -EINVAL; > + } > + > + child = device_get_next_child_node(dev, NULL); > + if (child) { > + res = fwnode_property_count_u32(child, "led-sources"); > + if (res > 0) { > + fwnode_property_read_u32_array(child, "led-sources", > + strings, res); > + > + /* set all strings as disabled, then enable those in led-sources*/ > + maxim->strings_mask = 0xf; > + for (i = 0; i < res; i++) { > + if (strings[i] <= 4) > + maxim->strings_mask &= ~BIT(strings[i]); > + } > + } > + > + fwnode_property_read_u32(child, "default-brightness", > + initial_brightness); > + > + fwnode_handle_put(child); > + } > + > + maxim->iset = MAX25014_ISET_DEFAULT_100; > + of_property_read_u32(node, "maxim,iset", &maxim->iset); > + > + if (maxim->iset < 0 || maxim->iset > 15) { > + dev_err(dev, > + "Invalid iset, should be a value from 0-15, entered was %d\n", > + maxim->iset); > + return -EINVAL; > + } > + > + if (*initial_brightness < 0 || *initial_brightness > 100) { > + dev_err(dev, > + "Invalid initial brightness, should be a value from 0-100, entered was %d\n", > + *initial_brightness); > + return -EINVAL; > + } > + > + return 0; > +} > + > +static int max25014_probe(struct i2c_client *cl) > +{ > + struct backlight_device *bl; > + const struct i2c_device_id *id = i2c_client_get_device_id(cl); > + struct max25014 *maxim; > + struct backlight_properties props; > + int ret; > + uint32_t initial_brightness = 50; > + > + maxim = devm_kzalloc(&cl->dev, sizeof(struct max25014), GFP_KERNEL); > + if (!maxim) > + return -ENOMEM; > + > + maxim->client = cl; > + > + ret = max25014_parse_dt(maxim, &initial_brightness); > + if (ret < 0) > + return ret; > + > + maxim->vin = devm_regulator_get_optional(&maxim->client->dev, "power"); I would have expected to see devm_regulator_get() here. Why do you care whether you get a real regulator or a dummy if you just NULL check maxim->vin everywhere? > + if (IS_ERR(maxim->vin)) { > + if (PTR_ERR(maxim->vin) == -EPROBE_DEFER) > + return -EPROBE_DEFER; > + maxim->vin = NULL; > + } > + > + if (maxim->vin) { If you had called devm_regulator_get() there would be no need for a NULL check here. > + ret = regulator_enable(maxim->vin); > + if (ret < 0) { > + dev_err(&maxim->client->dev, > + "failed to enable Vin: %d\n", ret); > + return ret; > + } > + } > + > + maxim->enable = devm_gpiod_get_optional(&maxim->client->dev, "enable", > + GPIOD_ASIS); > + if (IS_ERR(maxim->enable)) { > + ret = PTR_ERR(maxim->enable); > + dev_err(&maxim->client->dev, "failed to get enable gpio: %d\n", > + ret); > + goto disable_vin; > + } > + > + if (maxim->enable) > + gpiod_set_value_cansleep(maxim->enable, 1); No need for NULL pointer check here (see https://elixir.bootlin.com/linux/v6.18-rc4/source/drivers/gpio/gpiolib.c#L358-L363 ). > + > + /* Enable can be tied to vin rail wait if either is available */ > + if (maxim->enable || maxim->vin) { > + /* Datasheet Electrical Characteristics tSTARTUP 2ms */ > + usleep_range(2000, 2500); > + } If you really want to keep the devm_regulator_get_optional() I guess maybe you could persuade me it's need to avoid this sleep... although I'd be fairly happy to remove the NULL checks here too! > + > + maxim->regmap = devm_regmap_init_i2c(cl, &max25014_regmap_config); > + if (IS_ERR(maxim->regmap)) { > + ret = PTR_ERR(maxim->regmap); > + dev_err(&maxim->client->dev, > + "failed to initialize the i2c regmap: %d\n", ret); > + goto disable_full; > + } > + > + i2c_set_clientdata(cl, maxim); > + > + ret = max25014_check_errors(maxim); > + if (ret) { /* error is already reported in the above function */ > + goto disable_full; > + } > + > + ret = max25014_configure(maxim); > + if (ret) { > + dev_err(&maxim->client->dev, "device config err: %d", ret); > + goto disable_full; > + } > + > + memset(&props, 0, sizeof(props)); > + props.type = BACKLIGHT_PLATFORM; > + props.max_brightness = MAX_BRIGHTNESS; > + props.brightness = initial_brightness; > + props.scale = BACKLIGHT_SCALE_LINEAR; > + > + bl = devm_backlight_device_register(&maxim->client->dev, id->name, > + &maxim->client->dev, maxim, > + &max25014_bl_ops, &props); > + if (IS_ERR(bl)) > + return PTR_ERR(bl); > + > + maxim->bl = bl; > + > + return 0; > + > +disable_full: > + if (maxim->enable) > + gpiod_set_value_cansleep(maxim->enable, 0); Again, NULL check isn't needed. > +disable_vin: > + if (maxim->vin) > + regulator_disable(maxim->vin); > + return ret; > +} > + > +static void max25014_remove(struct i2c_client *cl) > +{ > + struct max25014 *maxim = i2c_get_clientdata(cl); > + > + maxim->bl->props.brightness = 0; > + max25014_update_status(maxim->bl); > + if (maxim->enable) > + gpiod_set_value_cansleep(maxim->enable, 0); Lose the NULL check. > + if (maxim->vin) > + regulator_disable(maxim->vin); > +} > + > +static const struct of_device_id max25014_dt_ids[] = { > + { .compatible = "maxim,max25014", }, > + { } > +}; > +MODULE_DEVICE_TABLE(of, max25014_dt_ids); > + > +static const struct i2c_device_id max25014_ids[] = { > + { "max25014" }, > + { } > +}; > +MODULE_DEVICE_TABLE(i2c, max25014_ids); > + > +static struct i2c_driver max25014_driver = { > + .driver = { > + .name = KBUILD_MODNAME, > + .of_match_table = of_match_ptr(max25014_dt_ids), > + }, > + .probe = max25014_probe, > + .remove = max25014_remove, > + .id_table = max25014_ids, > +}; > +module_i2c_driver(max25014_driver); > + > +MODULE_DESCRIPTION("Maxim MAX25014 backlight driver"); > +MODULE_AUTHOR("Maud Spierings "); > +MODULE_LICENSE("GPL"); Daniel.