drivers/mfd/pcf50633-adc.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* NXP PCF50633 ADC Driver
 *
 * (C) 2006-2008 by Openmoko, Inc.
 * Author: Balaji Rao <balajirrao@openmoko.org>
 * All rights reserved.
 *
 * Broken down from monstrous PCF50633 driver mainly by
 * Harald Welte, Andy Green and Werner Almesberger
 *
 *  NOTE: This driver does not yet support subtractive ADC mode, which means
 *  you can do only one measurement per read request.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/completion.h>

#include <linux/mfd/pcf50633/core.h>
#include <linux/mfd/pcf50633/adc.h>

struct pcf50633_adc_request {
	int mux;
	int avg;
	void (*callback)(struct pcf50633 *, void *, int);
	void *callback_param;
};

struct pcf50633_adc_sync_request {
	int result;
	struct completion completion;
};

#define PCF50633_MAX_ADC_FIFO_DEPTH 8

struct pcf50633_adc {
	struct pcf50633 *pcf;

	/* Private stuff */
	struct pcf50633_adc_request *queue[PCF50633_MAX_ADC_FIFO_DEPTH];
	int queue_head;
	int queue_tail;
	struct mutex queue_mutex;
};

static inline struct pcf50633_adc *__to_adc(struct pcf50633 *pcf)
{
	return platform_get_drvdata(pcf->adc_pdev);
}

static void adc_setup(struct pcf50633 *pcf, int channel, int avg)
{
	channel &= PCF50633_ADCC1_ADCMUX_MASK;

	/* kill ratiometric, but enable ACCSW biasing */
	pcf50633_reg_write(pcf, PCF50633_REG_ADCC2, 0x00);
	pcf50633_reg_write(pcf, PCF50633_REG_ADCC3, 0x01);

	/* start ADC conversion on selected channel */
	pcf50633_reg_write(pcf, PCF50633_REG_ADCC1, channel | avg |
		    PCF50633_ADCC1_ADCSTART | PCF50633_ADCC1_RES_10BIT);
}

static void trigger_next_adc_job_if_any(struct pcf50633 *pcf)
{
	struct pcf50633_adc *adc = __to_adc(pcf);
	int head;

	head = adc->queue_head;

	if (!adc->queue[head])
		return;

	adc_setup(pcf, adc->queue[head]->mux, adc->queue[head]->avg);
}

static int
adc_enqueue_request(struct pcf50633 *pcf, struct pcf50633_adc_request *req)
{
	struct pcf50633_adc *adc = __to_adc(pcf);
	int head, tail;

	mutex_lock(&adc->queue_mutex);

	head = adc->queue_head;
	tail = adc->queue_tail;

	if (adc->queue[tail]) {
		mutex_unlock(&adc->queue_mutex);
		dev_err(pcf->dev, "ADC queue is full, dropping request\n");
		return -EBUSY;
	}

	adc->queue[tail] = req;
	if (head == tail)
		trigger_next_adc_job_if_any(pcf);
	adc->queue_tail = (tail + 1) & (PCF50633_MAX_ADC_FIFO_DEPTH - 1);

	mutex_unlock(&adc->queue_mutex);

	return 0;
}

static void pcf50633_adc_sync_read_callback(struct pcf50633 *pcf, void *param,
	int result)
{
	struct pcf50633_adc_sync_request *req = param;

	req->result = result;
	complete(&req->completion);
}

int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg)
{
	struct pcf50633_adc_sync_request req;
	int ret;

	init_completion(&req.completion);

	ret = pcf50633_adc_async_read(pcf, mux, avg,
		pcf50633_adc_sync_read_callback, &req);
	if (ret)
		return ret;

	wait_for_completion(&req.completion);

	return req.result;
}
EXPORT_SYMBOL_GPL(pcf50633_adc_sync_read);

int pcf50633_adc_async_read(struct pcf50633 *pcf, int mux, int avg,
			     void (*callback)(struct pcf50633 *, void *, int),
			     void *callback_param)
{
	struct pcf50633_adc_request *req;
	int ret;

	/* req is freed when the result is ready, in interrupt handler */
	req = kmalloc(sizeof(*req), GFP_KERNEL);
	if (!req)
		return -ENOMEM;

	req->mux = mux;
	req->avg = avg;
	req->callback = callback;
	req->callback_param = callback_param;

	ret = adc_enqueue_request(pcf, req);
	if (ret)
		kfree(req);

	return ret;
}
EXPORT_SYMBOL_GPL(pcf50633_adc_async_read);

static int adc_result(struct pcf50633 *pcf)
{
	u8 adcs1, adcs3;
	u16 result;

	adcs1 = pcf50633_reg_read(pcf, PCF50633_REG_ADCS1);
	adcs3 = pcf50633_reg_read(pcf, PCF50633_REG_ADCS3);
	result = (adcs1 << 2) | (adcs3 & PCF50633_ADCS3_ADCDAT1L_MASK);

	dev_dbg(pcf->dev, "adc result = %d\n", result);

	return result;
}

static void pcf50633_adc_irq(int irq, void *data)
{
	struct pcf50633_adc *adc = data;
	struct pcf50633 *pcf = adc->pcf;
	struct pcf50633_adc_request *req;
	int head, res;

	mutex_lock(&adc->queue_mutex);
	head = adc->queue_head;

	req = adc->queue[head];
	if (WARN_ON(!req)) {
		dev_err(pcf->dev, "pcf50633-adc irq: ADC queue empty!\n");
		mutex_unlock(&adc->queue_mutex);
		return;
	}
	adc->queue[head] = NULL;
	adc->queue_head = (head + 1) &
				      (PCF50633_MAX_ADC_FIFO_DEPTH - 1);

	res = adc_result(pcf);
	trigger_next_adc_job_if_any(pcf);

	mutex_unlock(&adc->queue_mutex);

	req->callback(pcf, req->callback_param, res);
	kfree(req);
}

static int pcf50633_adc_probe(struct platform_device *pdev)
{
	struct pcf50633_adc *adc;

	adc = devm_kzalloc(&pdev->dev, sizeof(*adc), GFP_KERNEL);
	if (!adc)
		return -ENOMEM;

	adc->pcf = dev_to_pcf50633(pdev->dev.parent);
	platform_set_drvdata(pdev, adc);

	pcf50633_register_irq(adc->pcf, PCF50633_IRQ_ADCRDY,
					pcf50633_adc_irq, adc);

	mutex_init(&adc->queue_mutex);

	return 0;
}

static int pcf50633_adc_remove(struct platform_device *pdev)
{
	struct pcf50633_adc *adc = platform_get_drvdata(pdev);
	int i, head;

	pcf50633_free_irq(adc->pcf, PCF50633_IRQ_ADCRDY);

	mutex_lock(&adc->queue_mutex);
	head = adc->queue_head;

	if (WARN_ON(adc->queue[head]))
		dev_err(adc->pcf->dev,
			"adc driver removed with request pending\n");

	for (i = 0; i < PCF50633_MAX_ADC_FIFO_DEPTH; i++)
		kfree(adc->queue[i]);

	mutex_unlock(&adc->queue_mutex);

	return 0;
}

static struct platform_driver pcf50633_adc_driver = {
	.driver = {
		.name = "pcf50633-adc",
	},
	.probe = pcf50633_adc_probe,
	.remove = pcf50633_adc_remove,
};

module_platform_driver(pcf50633_adc_driver);

MODULE_AUTHOR("Balaji Rao <balajirrao@openmoko.org>");
MODULE_DESCRIPTION("PCF50633 adc driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pcf50633-adc");