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linux/drivers/mfd/pcf50633-adc.c
Paul Fertser bd8ef10261 mfd: revise locking for pcf50633 ADC 
Current implementation is prone to races, this patch attempts to remove all
but one (in pcf50633_adc_sync_read).

The idea is that we need to guard the queue access only on inserting and
removing items. If we insert and there're no more items in the queue it
means that the last irq already happened and we need to trigger ADC
manually. If not, then the next conversion will be triggered by the irq
handler upon completion of the previous.

Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
2009-09-17 09:46:53 +02:00

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6.4 KiB
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/* 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
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* 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/module.h>
#include <linux/init.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;
int result;
void (*callback)(struct pcf50633 *, void *, int);
void *callback_param;
/* Used in case of sync requests */
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_request *req = param;
req->result = result;
complete(&req->completion);
}
int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg)
{
struct pcf50633_adc_request *req;
int err;
/* req is freed when the result is ready, in interrupt handler */
req = kzalloc(sizeof(*req), GFP_KERNEL);
if (!req)
return -ENOMEM;
req->mux = mux;
req->avg = avg;
req->callback = pcf50633_adc_sync_read_callback;
req->callback_param = req;
init_completion(&req->completion);
err = adc_enqueue_request(pcf, req);
if (err)
return err;
wait_for_completion(&req->completion);
/* FIXME by this time req might be already freed */
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;
/* 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;
return adc_enqueue_request(pcf, req);
}
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 __devinit pcf50633_adc_probe(struct platform_device *pdev)
{
struct pcf50633_subdev_pdata *pdata = pdev->dev.platform_data;
struct pcf50633_adc *adc;
adc = kzalloc(sizeof(*adc), GFP_KERNEL);
if (!adc)
return -ENOMEM;
adc->pcf = pdata->pcf;
platform_set_drvdata(pdev, adc);
pcf50633_register_irq(pdata->pcf, PCF50633_IRQ_ADCRDY,
pcf50633_adc_irq, adc);
mutex_init(&adc->queue_mutex);
return 0;
}
static int __devexit 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);
kfree(adc);
return 0;
}
static struct platform_driver pcf50633_adc_driver = {
.driver = {
.name = "pcf50633-adc",
},
.probe = pcf50633_adc_probe,
.remove = __devexit_p(pcf50633_adc_remove),
};
static int __init pcf50633_adc_init(void)
{
return platform_driver_register(&pcf50633_adc_driver);
}
module_init(pcf50633_adc_init);
static void __exit pcf50633_adc_exit(void)
{
platform_driver_unregister(&pcf50633_adc_driver);
}
module_exit(pcf50633_adc_exit);
MODULE_AUTHOR("Balaji Rao <balajirrao@openmoko.org>");
MODULE_DESCRIPTION("PCF50633 adc driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pcf50633-adc");
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