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>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index 68beadaabceb..2ca5a7bee04e 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -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,
@@ -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;