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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-12-19 16:28:29 +0100 |
|---|---|---|
| committer | Lee Jones <lee.jones@linaro.org> | 2014-01-07 08:41:15 +0000 |
| commit | 7e170c6e4f7501bea900aa66b2b27a6ce5001e25 (patch) | |
| tree | 76eea8291945b24d8bbbf215243f7239c9728a08 /drivers/iio | |
| parent | 3466bd2273b81a0a29d0e134ba1c78b64b84f40b (diff) | |
| download | lwn-7e170c6e4f7501bea900aa66b2b27a6ce5001e25.tar.gz lwn-7e170c6e4f7501bea900aa66b2b27a6ce5001e25.zip | |
mfd: ti_am335x_tscadc: Don't read back REG_SE
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>
Diffstat (limited to 'drivers/iio')
| -rw-r--r-- | drivers/iio/adc/ti_am335x_adc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c index ce8d03ac900f..95eef8e89979 100644 --- a/drivers/iio/adc/ti_am335x_adc.c +++ b/drivers/iio/adc/ti_am335x_adc.c @@ -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); @@ -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) { |