thermal: tsens: Check if the IP is correctly enabled by firmware

The SROT registers are initialised by the secure firmware at boot. We
don't have write access to the registers. Check if the block is enabled
before continuing.
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/qcom/tsens-common.c

@@ -12,6 +12,10 @@
 #include <linux/regmap.h>
 #include "tsens.h"
 
+/* SROT */
+#define TSENS_EN		BIT(0)
+
+/* TM */
 #define STATUS_OFFSET		0x30
 #define SN_ADDR_OFFSET		0x4
 #define SN_ST_TEMP_MASK		0x3ff
@@ -119,7 +123,10 @@ int __init init_common(struct tsens_device *tmdev)
 {
 	void __iomem *tm_base, *srot_base;
 	struct resource *res;
+	u32 code;
+	int ret;
 	struct platform_device *op = of_find_device_by_node(tmdev->dev->of_node);
+	u16 ctrl_offset = tmdev->reg_offsets[SROT_CTRL_OFFSET];
 
 	if (!op)
 		return -EINVAL;
@@ -151,5 +158,15 @@ int __init init_common(struct tsens_device *tmdev)
 	if (IS_ERR(tmdev->tm_map))
 		return PTR_ERR(tmdev->tm_map);
 
+	if (tmdev->srot_map) {
+		ret = regmap_read(tmdev->srot_map, ctrl_offset, &code);
+		if (ret)
+			return ret;
+		if (!(code & TSENS_EN)) {
+			dev_err(tmdev->dev, "tsens device is not enabled\n");
+			return -ENODEV;
+		}
+	}
+
 	return 0;
 }