linux-kernel - [PATCH 4.9 32/72] power: supply: axp288_fuel_gauge: Read 12 bit values 2 registers at a time

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Date:   Sun, 19 Nov 2017 15:38:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Sebastian Reichel <sre@...nel.org>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 32/72] power: supply: axp288_fuel_gauge: Read 12 bit values 2 registers at a time

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hans de Goede <hdegoede@...hat.com>


[ Upstream commit 248efcf00602f0282587999bcc221a872bd72530 ]

In order for the MSB -> LSB latching to work correctly we must read the
2 8 bit registers of a 12 bit value in one consecutive read.

This fixes voltage_ocv reporting inconsistent values on my tablet.

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Sebastian Reichel <sre@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/power/supply/axp288_fuel_gauge.c |   40 +++++++++++++++++--------------
 1 file changed, 22 insertions(+), 18 deletions(-)

--- a/drivers/power/supply/axp288_fuel_gauge.c
+++ b/drivers/power/supply/axp288_fuel_gauge.c
@@ -210,6 +210,22 @@ static int fuel_gauge_read_15bit_word(st
 	return ret & FG_15BIT_VAL_MASK;
 }
 
+static int fuel_gauge_read_12bit_word(struct axp288_fg_info *info, int reg)
+{
+	unsigned char buf[2];
+	int ret;
+
+	ret = regmap_bulk_read(info->regmap, reg, buf, 2);
+	if (ret < 0) {
+		dev_err(&info->pdev->dev, "Error reading reg 0x%02x err: %d\n",
+			reg, ret);
+		return ret;
+	}
+
+	/* 12-bit data values have upper 8 bits in buf[0], lower 4 in buf[1] */
+	return (buf[0] << 4) | ((buf[1] >> 4) & 0x0f);
+}
+
 static int pmic_read_adc_val(const char *name, int *raw_val,
 		struct axp288_fg_info *info)
 {
@@ -270,12 +286,9 @@ static int fuel_gauge_debug_show(struct
 	seq_printf(s, "    FG_RDC0[%02x] : %02x\n",
 		AXP288_FG_RDC0_REG,
 		fuel_gauge_reg_readb(info, AXP288_FG_RDC0_REG));
-	seq_printf(s, "    FG_OCVH[%02x] : %02x\n",
+	seq_printf(s, "     FG_OCV[%02x] : %04x\n",
 		AXP288_FG_OCVH_REG,
-		fuel_gauge_reg_readb(info, AXP288_FG_OCVH_REG));
-	seq_printf(s, "    FG_OCVL[%02x] : %02x\n",
-		AXP288_FG_OCVL_REG,
-		fuel_gauge_reg_readb(info, AXP288_FG_OCVL_REG));
+		fuel_gauge_read_12bit_word(info, AXP288_FG_OCVH_REG));
 	seq_printf(s, " FG_DES_CAP[%02x] : %04x\n",
 		AXP288_FG_DES_CAP1_REG,
 		fuel_gauge_read_15bit_word(info, AXP288_FG_DES_CAP1_REG));
@@ -532,21 +545,12 @@ temp_read_fail:
 
 static int fuel_gauge_get_vocv(struct axp288_fg_info *info, int *vocv)
 {
-	int ret, value;
-
-	/* 12-bit data value, upper 8 in OCVH, lower 4 in OCVL */
-	ret = fuel_gauge_reg_readb(info, AXP288_FG_OCVH_REG);
-	if (ret < 0)
-		goto vocv_read_fail;
-	value = ret << 4;
+	int ret;
 
-	ret = fuel_gauge_reg_readb(info, AXP288_FG_OCVL_REG);
-	if (ret < 0)
-		goto vocv_read_fail;
-	value |= (ret & 0xf);
+	ret = fuel_gauge_read_12bit_word(info, AXP288_FG_OCVH_REG);
+	if (ret >= 0)
+		*vocv = VOLTAGE_FROM_ADC(ret);
 
-	*vocv = VOLTAGE_FROM_ADC(value);
-vocv_read_fail:
 	return ret;
 }