Re: [PATCH v2 4/8] regulator: add Qualcomm LCDB driver

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 10/19/26 1:25 PM, Dmitry Baryshkov wrote:
> LCD panels on boards with PMI632, PM6150L or PM8150L take their bias
> rails from the LCDB block. Without a driver they only work as long as
> the bootloader has enabled it and nothing turns it off.

[...]

> +static bool qcom_lcdb_handle_sc(struct qcom_lcdb *lcdb)
> +{
> +	guard(mutex)(&lcdb->lock);
> +
> +	if (!lcdb->enabled_mask || lcdb->sc_disabled)
> +		return false;
> +
> +	qcom_lcdb_module_disable(lcdb);
> +
> +	if (ktime_us_delta(ktime_get(), lcdb->sc_time) > LCDB_SC_RESET_CNT_DLY_US) {
> +		lcdb->sc_count = 0;
> +	} else if (lcdb->sc_count > LCDB_SC_CNT_MAX) {
> +		dev_err(lcdb->dev, "persistent short circuit, keeping the outputs off\n");
> +		lcdb->sc_disabled = true;
> +		return true;
> +	}
> +
> +	lcdb->sc_count++;
> +	lcdb->sc_time = ktime_get();


GPT:

The commit message says to restart up to ten times within one second,
but sc_time is updated on every fault.

Konrad

> +
> +	if (qcom_lcdb_module_enable(lcdb)) {
> +		dev_err(lcdb->dev, "failed to recover from a short circuit\n");
> +		lcdb->sc_disabled = true;
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static irqreturn_t qcom_lcdb_sc_irq(int irq, void *data)
> +{
> +	struct qcom_lcdb *lcdb = data;
> +	unsigned int val;
> +	int ret, i;
> +
> +	ret = regmap_read(lcdb->regmap, lcdb->base + LCDB_INT_RT_STS, &val);
> +	if (ret || !(val & LCDB_SC_ERROR_RT_STS))
> +		return IRQ_HANDLED;
> +
> +	/* Blanking time, a real short circuit is still reported afterwards */
> +	usleep_range(2000, 2100);
> +
> +	ret = regmap_read(lcdb->regmap, lcdb->base + LCDB_INT_RT_STS, &val);
> +	if (ret || !(val & LCDB_SC_ERROR_RT_STS))
> +		return IRQ_HANDLED;
> +
> +	if (qcom_lcdb_handle_sc(lcdb)) {
> +		for (i = 0; i < LCDB_NUM_RAILS; i++)
> +			regulator_notifier_call_chain(lcdb->rdev[i],
> +						      REGULATOR_EVENT_FAIL, NULL);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int qcom_lcdb_hw_init(struct qcom_lcdb *lcdb)
> +{
> +	unsigned int val;
> +	int ret, i;
> +
> +	for (i = 0; i < LCDB_NUM_RAILS; i++) {
> +		ret = regmap_read(lcdb->regmap, lcdb->base + qcom_lcdb_vreg[i], &val);
> +		if (ret)
> +			return ret;
> +
> +		lcdb->uV[i] = qcom_lcdb_sel_to_uV(val & LCDB_OUTPUT_VOLTAGE_MASK);
> +	}
> +
> +	ret = regmap_read(lcdb->regmap, lcdb->base + LCDB_ENABLE_CTL1, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val & LCDB_MODULE_EN) {
> +		lcdb->enabled_mask = GENMASK(LCDB_NUM_RAILS - 1, 0);
> +		return 0;
> +	}
> +
> +	return regmap_set_bits(lcdb->regmap, lcdb->base + LCDB_MODULE_RDY,
> +			       LCDB_MODULE_RDY_BIT);
> +}
> +
> +static int qcom_lcdb_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct regulator_config cfg = {};
> +	struct qcom_lcdb *lcdb;
> +	int irq, ret, i;
> +
> +	lcdb = devm_kzalloc(dev, sizeof(*lcdb), GFP_KERNEL);
> +	if (!lcdb)
> +		return -ENOMEM;
> +
> +	lcdb->dev = dev;
> +
> +	lcdb->regmap = dev_get_regmap(dev->parent, NULL);
> +	if (!lcdb->regmap)
> +		return dev_err_probe(dev, -ENODEV, "failed to get the parent regmap\n");
> +
> +	ret = device_property_read_u32(dev, "reg", &lcdb->base);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to get the base address\n");
> +
> +	ret = devm_mutex_init(dev, &lcdb->lock);
> +	if (ret)
> +		return ret;
> +
> +	ret = qcom_lcdb_hw_init(lcdb);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to read the initial state\n");
> +
> +	cfg.dev = dev;
> +	cfg.regmap = lcdb->regmap;
> +	cfg.driver_data = lcdb;
> +
> +	for (i = 0; i < LCDB_NUM_RAILS; i++) {
> +		lcdb->rdev[i] = devm_regulator_register(dev, &qcom_lcdb_descs[i], &cfg);
> +		if (IS_ERR(lcdb->rdev[i]))
> +			return dev_err_probe(dev, PTR_ERR(lcdb->rdev[i]),
> +					     "failed to register %s\n",
> +					     qcom_lcdb_descs[i].name);
> +	}
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +
> +	return devm_request_threaded_irq(dev, irq, NULL, qcom_lcdb_sc_irq,
> +					 IRQF_ONESHOT, "lcdb-sc", lcdb);
> +}
> +
> +static const struct of_device_id qcom_lcdb_match[] = {
> +	{ .compatible = "qcom,pm8150l-lcdb" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, qcom_lcdb_match);
> +
> +static struct platform_driver qcom_lcdb_driver = {
> +	.driver = {
> +		.name = "qcom-lcdb-regulator",
> +		.of_match_table = qcom_lcdb_match,
> +	},
> +	.probe = qcom_lcdb_probe,
> +};
> +module_platform_driver(qcom_lcdb_driver);
> +
> +MODULE_DESCRIPTION("Qualcomm LCDB (LCD bias) regulator driver");
> +MODULE_LICENSE("GPL");
>