mfd: ti_am335x_tscadc: Reorder the initialization steps

TI AM335X TRM [1] states that most of the configuration should be set in
the control register in the first place, before actually enabling the
hardware with the subsystem enable bit.

So far only half of the configuration was made in the first step (before
enabling the "subsystem"), which does not make really sense. Also, the
probe and the resume patch were acting differently. Let's harmonize all
this by following these steps:
1/ Configure the CLKDIV register
2/ Configure the CTRL register
3/ Configure the idle configuration
4/ Really enable the device by rewriting the CTRL register with the
   subsystem enable bit set.

[1] https://www.ti.com/lit/pdf/spruh73Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211015081506.933180-22-miquel.raynal@bootlin.com

drivers/mfd/ti_am335x_tscadc.c

@@ -219,8 +219,6 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 
 	/* Set the control register bits */
 	ctrl = CNTRLREG_STEPCONFIGWRT |	CNTRLREG_STEPID;
-	regmap_write(tscadc->regmap, REG_CTRL, ctrl);
-
 	if (tsc_wires > 0) {
 		tscadc->tsc_wires = tsc_wires;
 		if (tsc_wires == 5)
@@ -228,6 +226,7 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 		else
 			ctrl |= CNTRLREG_4WIRE | CNTRLREG_TSCENB;
 	}
+	regmap_write(tscadc->regmap, REG_CTRL, ctrl);
 
 	tscadc_idle_config(tscadc);
 
@@ -313,9 +312,9 @@ static int __maybe_unused tscadc_resume(struct device *dev)
 	pm_runtime_get_sync(dev);
 
 	/* context restore */
-	ctrl = CNTRLREG_STEPCONFIGWRT |	CNTRLREG_STEPID;
-	regmap_write(tscadc->regmap, REG_CTRL, ctrl);
+	regmap_write(tscadc->regmap, REG_CLKDIV, tscadc->clk_div);
 
+	ctrl = CNTRLREG_STEPCONFIGWRT |	CNTRLREG_STEPID;
 	if (tscadc->tsc_wires > 0) {
 		if (tscadc->tsc_wires == 5)
 			ctrl |= CNTRLREG_5WIRE | CNTRLREG_TSCENB;
@@ -323,13 +322,13 @@ static int __maybe_unused tscadc_resume(struct device *dev)
 			ctrl |= CNTRLREG_4WIRE | CNTRLREG_TSCENB;
 	}
 
+	regmap_write(tscadc->regmap, REG_CTRL, ctrl);
+
 	tscadc_idle_config(tscadc);
 
 	ctrl |= CNTRLREG_TSCSSENB;
 	regmap_write(tscadc->regmap, REG_CTRL, ctrl);
 
-	regmap_write(tscadc->regmap, REG_CLKDIV, tscadc->clk_div);
-
 	return 0;
 }