linux/drivers/mfd/ti_am335x_tscadc.c
Sebastian Andrzej Siewior 7ca6740cd1 mfd: input: iio: ti_amm335x: Rework TSC/ADC synchronization
The ADC driver always programs all possible ADC values and discards
them except for the value IIO asked for. On the am335x-evm the driver
programs four values and it takes 500us to gather them. Reducing the number
of conversations down to the (required) one also reduces the busy loop down
to 125us.

This leads to another error, namely the FIFOCOUNT register is sometimes
(like one out of 10 attempts) not updated in time leading to EBUSY.
The next read has the FIFOCOUNT register updated.
Checking for the ADCSTAT register for being idle isn't a good choice either.
The problem is that if TSC is used at the same time, the HW completes the
conversation for ADC *and* before the driver noticed it, the HW begins to
perform a TSC conversation and so the driver never seen the HW idle. The
next time we would have two values in the FIFO but since the driver reads
everything we always see the current one.
So instead of polling for the IDLE bit in ADCStatus register, we should
check the FIFOCOUNT register. It should be one instead of zero because we
request one value.

This change in turn leads to another error. Sometimes if TSC & ADC are
used together the TSC starts generating interrupts even if nobody
actually touched the touchscreen. The interrupts seem valid because TSC's
FIFO is filled with values for each channel of the TSC. This condition stops
after a few ADC reads but will occur again. Not good.

On top of this (even without the changes I just mentioned) there is a ADC
& TSC lockup condition which was reported to me by Jeff Lance including the
following test case:
A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw"
and a mug on touch screen. With this setup, the hardware will lockup after
something between 20 minutes and it could take up to a couple of hours.
During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means
STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is
idle and busy at the same time which is an invalid condition.

For all this reasons I decided to rework this TSC/ADC part and add a
handshake / synchronization here:
First the ADC signals that it needs the HW and writes a 0 mask into the
SE register. The HW (if active) will complete the current conversation
and become idle. The TSC driver will gather the values from the FIFO
(woken up by an interrupt) and won't "enable" another conversation.
Instead it will wake up the ADC driver which is already waiting. The ADC
driver will start "its" conversation and once it is done, it will
enable the TSC steps so the TSC will work again.

After this rework I haven't observed the lockup so far. Plus the busy
loop has been reduced from 500us to 125us.

The continues-read mode remains unchanged.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
2014-01-07 08:45:00 +00:00

396 lines
10 KiB
C

/*
* TI Touch Screen / ADC MFD driver
*
* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
*
* 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 version 2.
*
* This program is distributed "as is" WITHOUT ANY WARRANTY of any
* kind, whether express or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/regmap.h>
#include <linux/mfd/core.h>
#include <linux/pm_runtime.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/sched.h>
#include <linux/mfd/ti_am335x_tscadc.h>
static unsigned int tscadc_readl(struct ti_tscadc_dev *tsadc, unsigned int reg)
{
unsigned int val;
regmap_read(tsadc->regmap_tscadc, reg, &val);
return val;
}
static void tscadc_writel(struct ti_tscadc_dev *tsadc, unsigned int reg,
unsigned int val)
{
regmap_write(tsadc->regmap_tscadc, reg, val);
}
static const struct regmap_config tscadc_regmap_config = {
.name = "ti_tscadc",
.reg_bits = 32,
.reg_stride = 4,
.val_bits = 32,
};
void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val)
{
unsigned long flags;
spin_lock_irqsave(&tsadc->reg_lock, flags);
tsadc->reg_se_cache = val;
if (tsadc->adc_waiting)
wake_up(&tsadc->reg_se_wait);
else if (!tsadc->adc_in_use)
tscadc_writel(tsadc, REG_SE, val);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache);
static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc)
{
DEFINE_WAIT(wait);
u32 reg;
/*
* disable TSC steps so it does not run while the ADC is using it. If
* write 0 while it is running (it just started or was already running)
* then it completes all steps that were enabled and stops then.
*/
tscadc_writel(tsadc, REG_SE, 0);
reg = tscadc_readl(tsadc, REG_ADCFSM);
if (reg & SEQ_STATUS) {
tsadc->adc_waiting = true;
prepare_to_wait(&tsadc->reg_se_wait, &wait,
TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&tsadc->reg_lock);
schedule();
spin_lock_irq(&tsadc->reg_lock);
finish_wait(&tsadc->reg_se_wait, &wait);
reg = tscadc_readl(tsadc, REG_ADCFSM);
WARN_ON(reg & SEQ_STATUS);
tsadc->adc_waiting = false;
}
tsadc->adc_in_use = true;
}
void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val)
{
spin_lock_irq(&tsadc->reg_lock);
am335x_tscadc_need_adc(tsadc);
tscadc_writel(tsadc, REG_SE, val);
spin_unlock_irq(&tsadc->reg_lock);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once);
void am335x_tsc_se_adc_done(struct ti_tscadc_dev *tsadc)
{
unsigned long flags;
spin_lock_irqsave(&tsadc->reg_lock, flags);
tsadc->adc_in_use = false;
tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_adc_done);
void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val)
{
unsigned long flags;
spin_lock_irqsave(&tsadc->reg_lock, flags);
tsadc->reg_se_cache &= ~val;
tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_clr);
static void tscadc_idle_config(struct ti_tscadc_dev *config)
{
unsigned int idleconfig;
idleconfig = STEPCONFIG_YNN | STEPCONFIG_INM_ADCREFM |
STEPCONFIG_INP_ADCREFM | STEPCONFIG_YPN;
tscadc_writel(config, REG_IDLECONFIG, idleconfig);
}
static int ti_tscadc_probe(struct platform_device *pdev)
{
struct ti_tscadc_dev *tscadc;
struct resource *res;
struct clk *clk;
struct device_node *node = pdev->dev.of_node;
struct mfd_cell *cell;
struct property *prop;
const __be32 *cur;
u32 val;
int err, ctrl;
int clock_rate;
int tsc_wires = 0, adc_channels = 0, total_channels;
int readouts = 0;
if (!pdev->dev.of_node) {
dev_err(&pdev->dev, "Could not find valid DT data.\n");
return -EINVAL;
}
node = of_get_child_by_name(pdev->dev.of_node, "tsc");
of_property_read_u32(node, "ti,wires", &tsc_wires);
of_property_read_u32(node, "ti,coordiante-readouts", &readouts);
node = of_get_child_by_name(pdev->dev.of_node, "adc");
of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {
adc_channels++;
if (val > 7) {
dev_err(&pdev->dev, " PIN numbers are 0..7 (not %d)\n",
val);
return -EINVAL;
}
}
total_channels = tsc_wires + adc_channels;
if (total_channels > 8) {
dev_err(&pdev->dev, "Number of i/p channels more than 8\n");
return -EINVAL;
}
if (total_channels == 0) {
dev_err(&pdev->dev, "Need atleast one channel.\n");
return -EINVAL;
}
if (readouts * 2 + 2 + adc_channels > 16) {
dev_err(&pdev->dev, "Too many step configurations requested\n");
return -EINVAL;
}
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
dev_err(&pdev->dev, "no memory resource defined.\n");
return -EINVAL;
}
/* Allocate memory for device */
tscadc = devm_kzalloc(&pdev->dev,
sizeof(struct ti_tscadc_dev), GFP_KERNEL);
if (!tscadc) {
dev_err(&pdev->dev, "failed to allocate memory.\n");
return -ENOMEM;
}
tscadc->dev = &pdev->dev;
err = platform_get_irq(pdev, 0);
if (err < 0) {
dev_err(&pdev->dev, "no irq ID is specified.\n");
goto ret;
} else
tscadc->irq = err;
res = devm_request_mem_region(&pdev->dev,
res->start, resource_size(res), pdev->name);
if (!res) {
dev_err(&pdev->dev, "failed to reserve registers.\n");
return -EBUSY;
}
tscadc->tscadc_base = devm_ioremap(&pdev->dev,
res->start, resource_size(res));
if (!tscadc->tscadc_base) {
dev_err(&pdev->dev, "failed to map registers.\n");
return -ENOMEM;
}
tscadc->regmap_tscadc = devm_regmap_init_mmio(&pdev->dev,
tscadc->tscadc_base, &tscadc_regmap_config);
if (IS_ERR(tscadc->regmap_tscadc)) {
dev_err(&pdev->dev, "regmap init failed\n");
err = PTR_ERR(tscadc->regmap_tscadc);
goto ret;
}
spin_lock_init(&tscadc->reg_lock);
init_waitqueue_head(&tscadc->reg_se_wait);
pm_runtime_enable(&pdev->dev);
pm_runtime_get_sync(&pdev->dev);
/*
* The TSC_ADC_Subsystem has 2 clock domains
* OCP_CLK and ADC_CLK.
* The ADC clock is expected to run at target of 3MHz,
* and expected to capture 12-bit data at a rate of 200 KSPS.
* The TSC_ADC_SS controller design assumes the OCP clock is
* at least 6x faster than the ADC clock.
*/
clk = clk_get(&pdev->dev, "adc_tsc_fck");
if (IS_ERR(clk)) {
dev_err(&pdev->dev, "failed to get TSC fck\n");
err = PTR_ERR(clk);
goto err_disable_clk;
}
clock_rate = clk_get_rate(clk);
clk_put(clk);
tscadc->clk_div = clock_rate / ADC_CLK;
/* TSCADC_CLKDIV needs to be configured to the value minus 1 */
tscadc->clk_div--;
tscadc_writel(tscadc, REG_CLKDIV, tscadc->clk_div);
/* Set the control register bits */
ctrl = CNTRLREG_STEPCONFIGWRT |
CNTRLREG_STEPID;
if (tsc_wires > 0)
ctrl |= CNTRLREG_4WIRE | CNTRLREG_TSCENB;
tscadc_writel(tscadc, REG_CTRL, ctrl);
/* Set register bits for Idle Config Mode */
if (tsc_wires > 0)
tscadc_idle_config(tscadc);
/* Enable the TSC module enable bit */
ctrl = tscadc_readl(tscadc, REG_CTRL);
ctrl |= CNTRLREG_TSCSSENB;
tscadc_writel(tscadc, REG_CTRL, ctrl);
tscadc->used_cells = 0;
tscadc->tsc_cell = -1;
tscadc->adc_cell = -1;
/* TSC Cell */
if (tsc_wires > 0) {
tscadc->tsc_cell = tscadc->used_cells;
cell = &tscadc->cells[tscadc->used_cells++];
cell->name = "TI-am335x-tsc";
cell->of_compatible = "ti,am3359-tsc";
cell->platform_data = &tscadc;
cell->pdata_size = sizeof(tscadc);
}
/* ADC Cell */
if (adc_channels > 0) {
tscadc->adc_cell = tscadc->used_cells;
cell = &tscadc->cells[tscadc->used_cells++];
cell->name = "TI-am335x-adc";
cell->of_compatible = "ti,am3359-adc";
cell->platform_data = &tscadc;
cell->pdata_size = sizeof(tscadc);
}
err = mfd_add_devices(&pdev->dev, pdev->id, tscadc->cells,
tscadc->used_cells, NULL, 0, NULL);
if (err < 0)
goto err_disable_clk;
device_init_wakeup(&pdev->dev, true);
platform_set_drvdata(pdev, tscadc);
return 0;
err_disable_clk:
pm_runtime_put_sync(&pdev->dev);
pm_runtime_disable(&pdev->dev);
ret:
return err;
}
static int ti_tscadc_remove(struct platform_device *pdev)
{
struct ti_tscadc_dev *tscadc = platform_get_drvdata(pdev);
tscadc_writel(tscadc, REG_SE, 0x00);
pm_runtime_put_sync(&pdev->dev);
pm_runtime_disable(&pdev->dev);
mfd_remove_devices(tscadc->dev);
return 0;
}
#ifdef CONFIG_PM
static int tscadc_suspend(struct device *dev)
{
struct ti_tscadc_dev *tscadc_dev = dev_get_drvdata(dev);
tscadc_writel(tscadc_dev, REG_SE, 0x00);
pm_runtime_put_sync(dev);
return 0;
}
static int tscadc_resume(struct device *dev)
{
struct ti_tscadc_dev *tscadc_dev = dev_get_drvdata(dev);
unsigned int restore, ctrl;
pm_runtime_get_sync(dev);
/* context restore */
ctrl = CNTRLREG_STEPCONFIGWRT | CNTRLREG_STEPID;
if (tscadc_dev->tsc_cell != -1)
ctrl |= CNTRLREG_TSCENB | CNTRLREG_4WIRE;
tscadc_writel(tscadc_dev, REG_CTRL, ctrl);
if (tscadc_dev->tsc_cell != -1)
tscadc_idle_config(tscadc_dev);
restore = tscadc_readl(tscadc_dev, REG_CTRL);
tscadc_writel(tscadc_dev, REG_CTRL,
(restore | CNTRLREG_TSCSSENB));
tscadc_writel(tscadc_dev, REG_CLKDIV, tscadc_dev->clk_div);
return 0;
}
static const struct dev_pm_ops tscadc_pm_ops = {
.suspend = tscadc_suspend,
.resume = tscadc_resume,
};
#define TSCADC_PM_OPS (&tscadc_pm_ops)
#else
#define TSCADC_PM_OPS NULL
#endif
static const struct of_device_id ti_tscadc_dt_ids[] = {
{ .compatible = "ti,am3359-tscadc", },
{ }
};
MODULE_DEVICE_TABLE(of, ti_tscadc_dt_ids);
static struct platform_driver ti_tscadc_driver = {
.driver = {
.name = "ti_am3359-tscadc",
.owner = THIS_MODULE,
.pm = TSCADC_PM_OPS,
.of_match_table = ti_tscadc_dt_ids,
},
.probe = ti_tscadc_probe,
.remove = ti_tscadc_remove,
};
module_platform_driver(ti_tscadc_driver);
MODULE_DESCRIPTION("TI touchscreen / ADC MFD controller driver");
MODULE_AUTHOR("Rachna Patil <rachna@ti.com>");
MODULE_LICENSE("GPL");