power: axp209: Add support for voltage rate control on LDO3
The AXP209 LDO3 regulator supports voltage rate control, or can set a
slew rate.
This allows for the power to gradually rise up to the desired voltage,
instead of spiking up as fast as possible. Reason to have this can be
to reduce the inrush currents for example.
There are 3 slopes to choose from, the default, 'none' is a voltage rise
of 0.0167 V/uS, a 1.6 mV/uS and a 0.8 mV/uS voltage rise.
In ideal world (where vendors follow the recommended design guidelines)
this setting should not be enabled by default. Unless of course AXP209
crashes instead of reporting overcurrent condition as it normally should
do in this case.
Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Priit Laes <plaes@plaes.org>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
diff --git a/drivers/power/axp209.c b/drivers/power/axp209.c
index 819b168..cf138fc 100644
--- a/drivers/power/axp209.c
+++ b/drivers/power/axp209.c
@@ -9,6 +9,16 @@
#include <asm/arch/pmic_bus.h>
#include <axp_pmic.h>
+#ifdef CONFIG_AXP_ALDO3_VOLT_SLOPE_08
+# define AXP209_VRC_SLOPE AXP209_VRC_LDO3_800uV_uS
+#endif
+#ifdef CONFIG_AXP_ALDO3_VOLT_SLOPE_16
+# define AXP209_VRC_SLOPE AXP209_VRC_LDO3_1600uV_uS
+#endif
+#if defined CONFIG_AXP_ALDO3_VOLT_SLOPE_NONE || !defined AXP209_VRC_SLOPE
+# define AXP209_VRC_SLOPE 0x00
+#endif
+
static u8 axp209_mvolt_to_cfg(int mvolt, int min, int max, int div)
{
if (mvolt < min)
@@ -98,6 +108,20 @@
return pmic_bus_clrbits(AXP209_OUTPUT_CTRL,
AXP209_OUTPUT_CTRL_LDO3);
+ /*
+ * Some boards have trouble reaching the target voltage without causing
+ * great inrush currents. To prevent this, boards can enable a certain
+ * slope to ramp up voltage. Note, this only works when changing an
+ * already active power rail. When toggling power on, the AXP ramps up
+ * steeply at 0.0167 V/uS.
+ */
+ rc = pmic_bus_read(AXP209_VRC_DCDC2_LDO3, &cfg);
+ cfg = AXP209_VRC_LDO3_SLOPE_SET(cfg, AXP209_VRC_SLOPE);
+ rc |= pmic_bus_write(AXP209_VRC_DCDC2_LDO3, cfg);
+
+ if (rc)
+ return rc;
+
if (mvolt == -1) {
cfg = AXP209_LDO3_VOLTAGE_FROM_LDO3IN;
} else {