thermal: ti-soc-thermal: Skip pointless register access for dra7

On dra7, there is no Start of Conversion (SOC) register bit and we have an
empty bgap_soc_mask in the configuration for the thermal driver. Let's not
do pointless reads and writes with the empty mask.

There's also no point waiting for End of Conversion bit (EOCZ) to go high
on dra7. We only care about it going down, and are now mostly timing out
waiting for EOCZ high while it has already gone down.

When we add checking for the timeout errors in a later patch, waiting for
EOCZ high would cause bogus time out errors.

Cc: Adam Ford <aford173@gmail.com>
Cc: Carl Philipp Klemm <philipp@uvos.xyz>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: H. Nikolaus Schaller <hns@goldelico.com>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Adam Ford <aford173@gmail.com> #logicpd-torpedo-37xx-devkit
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210205134534.49200-2-tony@atomide.com

drivers/thermal/ti-soc-thermal/ti-bandgap.c

@@ -602,29 +602,30 @@ void *ti_bandgap_get_sensor_data(struct ti_bandgap *bgp, int id)
 static int
 ti_bandgap_force_single_read(struct ti_bandgap *bgp, int id)
 {
-	u32 counter = 1000;
-	struct temp_sensor_registers *tsr;
+	struct temp_sensor_registers *tsr = bgp->conf->sensors[id].registers;
+	u32 counter;
 
 	/* Select single conversion mode */
 	if (TI_BANDGAP_HAS(bgp, MODE_CONFIG))
 		RMW_BITS(bgp, id, bgap_mode_ctrl, mode_ctrl_mask, 0);
 
-	/* Start of Conversion = 1 */
-	RMW_BITS(bgp, id, temp_sensor_ctrl, bgap_soc_mask, 1);
+	/* Set Start of Conversion if available */
+	if (tsr->bgap_soc_mask) {
+		RMW_BITS(bgp, id, temp_sensor_ctrl, bgap_soc_mask, 1);
 
-	/* Wait for EOCZ going up */
-	tsr = bgp->conf->sensors[id].registers;
+		/* Wait for EOCZ going up */
+		counter = 1000;
+		while (--counter) {
+			if (ti_bandgap_readl(bgp, tsr->temp_sensor_ctrl) &
+			    tsr->bgap_eocz_mask)
+				break;
+		}
 
-	while (--counter) {
-		if (ti_bandgap_readl(bgp, tsr->temp_sensor_ctrl) &
-		    tsr->bgap_eocz_mask)
-			break;
+		/* Clear Start of Conversion if available */
+		RMW_BITS(bgp, id, temp_sensor_ctrl, bgap_soc_mask, 0);
 	}
 
-	/* Start of Conversion = 0 */
-	RMW_BITS(bgp, id, temp_sensor_ctrl, bgap_soc_mask, 0);
-
-	/* Wait for EOCZ going down */
+	/* Wait for EOCZ going down, always needed even if no bgap_soc_mask */
 	counter = 1000;
 	while (--counter) {
 		if (!(ti_bandgap_readl(bgp, tsr->temp_sensor_ctrl) &