regulator/mfd: max14577: Export symbols for calculating charger current

This patch prepares for changing the max14577 charger driver to allow
configuring battery-dependent settings from DTS.

The patch moves from regulator driver to MFD core driver and exports:
 - function for calculating register value for charger's current;
 - table of limits for chargers (MAX14577, MAX77836).

Previously they were used only by the max14577 regulator driver. In next
patch the charger driver will use them as well. Exporting them will
reduce unnecessary code duplication.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Mark Brown <broonie@linaro.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 95 insertions, 0 deletions

diff --git a/drivers/mfd/max14577.c b/drivers/mfd/max14577.c
index 6599407b5624..b8af263be594 100644
--- a/drivers/mfd/max14577.c
+++ b/drivers/mfd/max14577.c
@@ -26,6 +26,87 @@
 #include <linux/mfd/max14577.h>
 #include <linux/mfd/max14577-private.h>
 
+/*
+ * Table of valid charger currents for different Maxim chipsets.
+ * It is placed here because it is used by both charger and regulator driver.
+ */
+const struct maxim_charger_current maxim_charger_currents[] = {
+	[MAXIM_DEVICE_TYPE_UNKNOWN] = { 0, 0, 0, 0 },
+	[MAXIM_DEVICE_TYPE_MAX14577] = {
+		.min		= MAX14577_CHARGER_CURRENT_LIMIT_MIN,
+		.high_start	= MAX14577_CHARGER_CURRENT_LIMIT_HIGH_START,
+		.high_step	= MAX14577_CHARGER_CURRENT_LIMIT_HIGH_STEP,
+		.max		= MAX14577_CHARGER_CURRENT_LIMIT_MAX,
+	},
+	[MAXIM_DEVICE_TYPE_MAX77836] = {
+		.min		= MAX77836_CHARGER_CURRENT_LIMIT_MIN,
+		.high_start	= MAX77836_CHARGER_CURRENT_LIMIT_HIGH_START,
+		.high_step	= MAX77836_CHARGER_CURRENT_LIMIT_HIGH_STEP,
+		.max		= MAX77836_CHARGER_CURRENT_LIMIT_MAX,
+	},
+};
+EXPORT_SYMBOL_GPL(maxim_charger_currents);
+
+/*
+ * maxim_charger_calc_reg_current - Calculate register value for current
+ * @limits:	constraints for charger, matching the MBCICHWRC register
+ * @min_ua:	minimal requested current, micro Amps
+ * @max_ua:	maximum requested current, micro Amps
+ * @dst:	destination to store calculated register value
+ *
+ * Calculates the value of MBCICHWRC (Fast Battery Charge Current) register
+ * for given current and stores it under pointed 'dst'. The stored value
+ * combines low bit (MBCICHWRCL) and high bits (MBCICHWRCH). It is also
+ * properly shifted.
+ *
+ * The calculated register value matches the current which:
+ *  - is always between <limits.min, limits.max>;
+ *  - is always less or equal to max_ua;
+ *  - is the highest possible value;
+ *  - may be lower than min_ua.
+ *
+ * On success returns 0. On error returns -EINVAL (requested min/max current
+ * is outside of given charger limits) and 'dst' is not set.
+ */
+int maxim_charger_calc_reg_current(const struct maxim_charger_current *limits,
+		unsigned int min_ua, unsigned int max_ua, u8 *dst)
+{
+	unsigned int current_bits = 0xf;
+
+	if (min_ua > max_ua)
+		return -EINVAL;
+
+	if (min_ua > limits->max || max_ua < limits->min)
+		return -EINVAL;
+
+	if (max_ua < limits->high_start) {
+		/*
+		 * Less than high_start, so set the minimal current
+		 * (turn Low Bit off, 0 as high bits).
+		 */
+		*dst = 0x0;
+		return 0;
+	}
+
+	/* max_ua is in range: <high_start, infinite>, cut it to limits.max */
+	max_ua = min(limits->max, max_ua);
+	max_ua -= limits->high_start;
+	/*
+	 * There is no risk of overflow 'max_ua' here because:
+	 *  - max_ua >= limits.high_start
+	 *  - BUILD_BUG checks that 'limits' are: max >= high_start + high_step
+	 */
+	current_bits = max_ua / limits->high_step;
+
+	/* Turn Low Bit on (use range <limits.high_start, limits.max>) ... */
+	*dst = 0x1 << CHGCTRL4_MBCICHWRCL_SHIFT;
+	/* and set proper High Bits */
+	*dst |= current_bits << CHGCTRL4_MBCICHWRCH_SHIFT;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(maxim_charger_calc_reg_current);
+
 static const struct mfd_cell max14577_devs[] = {
 	{
 		.name = "max14577-muic",
@@ -466,6 +547,20 @@ static int __init max14577_i2c_init(void)
 	BUILD_BUG_ON(ARRAY_SIZE(max14577_i2c_id) != MAXIM_DEVICE_TYPE_NUM);
 	BUILD_BUG_ON(ARRAY_SIZE(max14577_dt_match) != MAXIM_DEVICE_TYPE_NUM);
 
+	/* Valid charger current values must be provided for each chipset */
+	BUILD_BUG_ON(ARRAY_SIZE(maxim_charger_currents) != MAXIM_DEVICE_TYPE_NUM);
+
+	/* Check for valid values for charger */
+	BUILD_BUG_ON(MAX14577_CHARGER_CURRENT_LIMIT_HIGH_START +
+			MAX14577_CHARGER_CURRENT_LIMIT_HIGH_STEP * 0xf !=
+			MAX14577_CHARGER_CURRENT_LIMIT_MAX);
+	BUILD_BUG_ON(MAX14577_CHARGER_CURRENT_LIMIT_HIGH_STEP == 0);
+
+	BUILD_BUG_ON(MAX77836_CHARGER_CURRENT_LIMIT_HIGH_START +
+			MAX77836_CHARGER_CURRENT_LIMIT_HIGH_STEP * 0xf !=
+			MAX77836_CHARGER_CURRENT_LIMIT_MAX);
+	BUILD_BUG_ON(MAX77836_CHARGER_CURRENT_LIMIT_HIGH_STEP == 0);
+
 	return i2c_add_driver(&max14577_i2c_driver);
 }
 subsys_initcall(max14577_i2c_init);