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mfd: ti_am335x_tscadc: Don't read back REG_SE
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The purpose of reg_se_cache has been defeated. It should avoid the
read-back of the register to avoid the latency and the fact that the
bits are reset to 0 after the individual conversation took place.

The reason why this is required like this to work, is that read-back of
the register removes the bits of the ADC so they do not start another
conversation after the register is re-written from the TSC side for the
update.
To avoid the not required read-back I introduce a "set once" variant which
does not update the cache mask. After the conversation completes, the
bit is removed from the SE register anyway and we don't plan a new
conversation "any time soon". The current set function is renamed to
set_cache to distinguish the two operations.
This is a small preparation for a larger sync-rework.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
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Sebastian Andrzej Siewior authored and Lee Jones committed Jan 7, 2014
1 parent 3466bd2 commit 7e170c6
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Showing 4 changed files with 18 additions and 9 deletions.
4 changes: 2 additions & 2 deletions drivers/iio/adc/ti_am335x_adc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -181,7 +181,7 @@ static int tiadc_buffer_postenable(struct iio_dev *indio_dev)
enb |= (get_adc_step_bit(adc_dev, bit) << 1);
adc_dev->buffer_en_ch_steps = enb;

am335x_tsc_se_set(adc_dev->mfd_tscadc, enb);
am335x_tsc_se_set_cache(adc_dev->mfd_tscadc, enb);

tiadc_writel(adc_dev, REG_IRQSTATUS, IRQENB_FIFO1THRES
| IRQENB_FIFO1OVRRUN | IRQENB_FIFO1UNDRFLW);
Expand Down Expand Up @@ -332,7 +332,7 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
return -EBUSY;

step_en = get_adc_step_mask(adc_dev);
am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
am335x_tsc_se_set_once(adc_dev->mfd_tscadc, step_en);

/* Wait for ADC sequencer to complete sampling */
while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
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4 changes: 2 additions & 2 deletions drivers/input/touchscreen/ti_am335x_tsc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -198,7 +198,7 @@ static void titsc_step_config(struct titsc *ts_dev)
/* The steps1 … end and bit 0 for TS_Charge */
stepenable = (1 << (end_step + 2)) - 1;
ts_dev->step_mask = stepenable;
am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
}

static void titsc_read_coordinates(struct titsc *ts_dev,
Expand Down Expand Up @@ -322,7 +322,7 @@ static irqreturn_t titsc_irq(int irq, void *dev)

if (irqclr) {
titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
am335x_tsc_se_set(ts_dev->mfd_tscadc, ts_dev->step_mask);
am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
return IRQ_HANDLED;
}
return IRQ_NONE;
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16 changes: 12 additions & 4 deletions drivers/mfd/ti_am335x_tscadc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -53,24 +53,32 @@ static void am335x_tsc_se_update(struct ti_tscadc_dev *tsadc)
tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache);
}

void am335x_tsc_se_set(struct ti_tscadc_dev *tsadc, u32 val)
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 = tscadc_readl(tsadc, REG_SE);
tsadc->reg_se_cache |= val;
am335x_tsc_se_update(tsadc);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_set);
EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache);

void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val)
{
unsigned long flags;

spin_lock_irqsave(&tsadc->reg_lock, flags);
tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache | val);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
}
EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once);

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 = tscadc_readl(tsadc, REG_SE);
tsadc->reg_se_cache &= ~val;
am335x_tsc_se_update(tsadc);
spin_unlock_irqrestore(&tsadc->reg_lock, flags);
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3 changes: 2 additions & 1 deletion include/linux/mfd/ti_am335x_tscadc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -176,7 +176,8 @@ static inline struct ti_tscadc_dev *ti_tscadc_dev_get(struct platform_device *p)
return *tscadc_dev;
}

void am335x_tsc_se_set(struct ti_tscadc_dev *tsadc, u32 val);
void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val);
void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val);
void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val);

#endif

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