mfd: ti_am335x_tscadc: Introduce a helper to deal with the type of hardware

One way of knowing which hardware we are dealing with is to check the
compatible string. When this must be done at several places, it's best
and certainly more clear to use a helper for that.

Introduce ti_adc_with_touchscreen() to indicate if there is a touchscreen
controller available (meaning it's an am33xx-like ADC). This helper does
not indicate if it is actually used (that is the purpose of the use_tsc
boolean).

Introducing this helper helps making a difference in the code between
what is generic to both types of ADCs and what is specific to the am33xx
hardware before introducing support for the am437x hardware.
Signed-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/20211015081506.933180-36-miquel.raynal@bootlin.com

drivers/mfd/ti_am335x_tscadc.c

@@ -105,8 +105,9 @@ static void tscadc_idle_config(struct ti_tscadc_dev *tscadc)
 {
 	unsigned int idleconfig;
 
-	idleconfig = STEPCONFIG_YNN | STEPCONFIG_INM_ADCREFM |
-			STEPCONFIG_INP_ADCREFM | STEPCONFIG_YPN;
+	idleconfig = STEPCONFIG_INM_ADCREFM | STEPCONFIG_INP_ADCREFM;
+	if (ti_adc_with_touchscreen(tscadc))
+		idleconfig |= STEPCONFIG_YNN | STEPCONFIG_YPN;
 
 	regmap_write(tscadc->regmap, REG_IDLECONFIG, idleconfig);
 }
@@ -140,12 +141,14 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 
 	tscadc->data = of_device_get_match_data(&pdev->dev);
 
+	if (ti_adc_with_touchscreen(tscadc)) {
 		node = of_get_child_by_name(pdev->dev.of_node, "tsc");
 		of_property_read_u32(node, "ti,wires", &tscmag_wires);
 		of_property_read_u32(node, "ti,coordiante-readouts", &readouts);
 		of_node_put(node);
 		if (tscmag_wires)
 			use_tsc = true;
+	}
 
 	node = of_get_child_by_name(pdev->dev.of_node, "adc");
 	of_property_for_each_u32(node, "ti,adc-channels", prop, cur, val) {
@@ -225,7 +228,9 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 	 * of the CTRL register but not the subsystem enable bit which must be
 	 * added manually when timely.
 	 */
-	tscadc->ctrl = CNTRLREG_TSC_STEPCONFIGWRT | CNTRLREG_STEPID;
+	tscadc->ctrl = CNTRLREG_STEPID;
+	if (ti_adc_with_touchscreen(tscadc)) {
+		tscadc->ctrl |= CNTRLREG_TSC_STEPCONFIGWRT;
 		if (use_tsc) {
 			tscadc->ctrl |= CNTRLREG_TSC_ENB;
 			if (tscmag_wires == 5)
@@ -233,6 +238,7 @@ static	int ti_tscadc_probe(struct platform_device *pdev)
 			else
 				tscadc->ctrl |= CNTRLREG_TSC_4WIRE;
 		}
+	}
 	regmap_write(tscadc->regmap, REG_CTRL, tscadc->ctrl);
 
 	tscadc_idle_config(tscadc);

include/linux/mfd/ti_am335x_tscadc.h

@@ -177,6 +177,12 @@ static inline struct ti_tscadc_dev *ti_tscadc_dev_get(struct platform_device *p)
 	return *tscadc_dev;
 }
 
+static inline bool ti_adc_with_touchscreen(struct ti_tscadc_dev *tscadc)
+{
+	return of_device_is_compatible(tscadc->dev->of_node,
+				       "ti,am3359-tscadc");
+}
+
 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);