drivers/rtc/rtc-isl12057.c: report error code upon failure in dev_err() calls

As pointed out by Mark, it is generally useful to log the error code when
reporting a failure.  This patch improves existing calls to dev_err() in
ISL12057 driver to also report error code.
Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Suggested-by: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Peter Huewe <peter.huewe@infineon.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Grant Likely <grant.likely@linaro.org>
Acked-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-isl12057.c

@@ -170,8 +170,8 @@ static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	mutex_lock(&data->lock);
 	ret = regmap_read(data->regmap, ISL12057_REG_SR, &sr);
 	if (ret) {
-		dev_err(dev, "%s: unable to read oscillator status flag\n",
-			__func__);
+		dev_err(dev, "%s: unable to read oscillator status flag (%d)\n",
+			__func__, ret);
 		goto out;
 	} else {
 		if (sr & ISL12057_REG_SR_OSF) {
@@ -183,7 +183,8 @@ static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	ret = regmap_bulk_read(data->regmap, ISL12057_REG_RTC_SC, regs,
 			       ISL12057_RTC_SEC_LEN);
 	if (ret)
-		dev_err(dev, "%s: unable to read RTC time\n", __func__);
+		dev_err(dev, "%s: unable to read RTC time section (%d)\n",
+			__func__, ret);
 
 out:
 	mutex_unlock(&data->lock);
@@ -210,7 +211,8 @@ static int isl12057_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	ret = regmap_bulk_write(data->regmap, ISL12057_REG_RTC_SC, regs,
 				ISL12057_RTC_SEC_LEN);
 	if (ret) {
-		dev_err(dev, "%s: writing RTC time failed\n", __func__);
+		dev_err(dev, "%s: unable to write RTC time section (%d)\n",
+			__func__, ret);
 		goto out;
 	}
 
@@ -221,7 +223,8 @@ static int isl12057_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	ret = regmap_update_bits(data->regmap, ISL12057_REG_SR,
 				 ISL12057_REG_SR_OSF, 0);
 	if (ret < 0)
-		dev_err(dev, "Unable to clear oscillator failure bit\n");
+		dev_err(dev, "%s: unable to clear osc. failure bit (%d)\n",
+			__func__, ret);
 
 out:
 	mutex_unlock(&data->lock);
@@ -242,7 +245,8 @@ static int isl12057_check_rtc_status(struct device *dev, struct regmap *regmap)
 	ret = regmap_update_bits(regmap, ISL12057_REG_INT,
 				 ISL12057_REG_INT_EOSC, 0);
 	if (ret < 0) {
-		dev_err(dev, "Unable to enable oscillator\n");
+		dev_err(dev, "%s: unable to enable oscillator (%d)\n",
+			__func__, ret);
 		return ret;
 	}
 
@@ -250,7 +254,8 @@ static int isl12057_check_rtc_status(struct device *dev, struct regmap *regmap)
 	ret = regmap_update_bits(regmap, ISL12057_REG_SR,
 				 ISL12057_REG_SR_A1F, 0);
 	if (ret < 0) {
-		dev_err(dev, "Unable to clear alarm bit\n");
+		dev_err(dev, "%s: unable to clear alarm bit (%d)\n",
+			__func__, ret);
 		return ret;
 	}
 
@@ -284,7 +289,8 @@ static int isl12057_probe(struct i2c_client *client,
 	regmap = devm_regmap_init_i2c(client, &isl12057_rtc_regmap_config);
 	if (IS_ERR(regmap)) {
 		ret = PTR_ERR(regmap);
-		dev_err(dev, "regmap allocation failed: %d\n", ret);
+		dev_err(dev, "%s: regmap allocation failed (%d)\n",
+			__func__, ret);
 		return ret;
 	}