mfd: pm8xxx-misc: add an API to preload the dVdd regulator
Add a new API, pm8xxx_preload_dVdd, which will preload the dVdd
regulator on PMIC PM8901 chips during off state. This can help
to reduce fluctuations in the dVdd voltage during startup at the
cost of additional off state current draw.
This API should only be called if dVdd startup issues are
suspected.
Change-Id: Ic7ee60539de37a761bb9ca6c5200327a7b99da89
CRs-Fixed: 326086
Signed-off-by: David Collins <collinsd@codeaurora.org>
diff --git a/drivers/mfd/pm8xxx-misc.c b/drivers/mfd/pm8xxx-misc.c
index 7314c7e..283f985 100644
--- a/drivers/mfd/pm8xxx-misc.c
+++ b/drivers/mfd/pm8xxx-misc.c
@@ -944,6 +944,63 @@
}
EXPORT_SYMBOL(pm8xxx_uart_gpio_mux_ctrl);
+static int __pm8901_preload_dVdd(struct pm8xxx_misc_chip *chip)
+{
+ int rc;
+
+ rc = pm8xxx_writeb(chip->dev->parent, 0x0BD, 0x0F);
+ if (rc)
+ pr_err("pm8xxx_writeb failed for 0x0BD, rc=%d\n", rc);
+
+ rc = pm8xxx_writeb(chip->dev->parent, 0x001, 0xB4);
+ if (rc)
+ pr_err("pm8xxx_writeb failed for 0x001, rc=%d\n", rc);
+
+ pr_info("dVdd preloaded\n");
+
+ return rc;
+}
+
+/**
+ * pm8xxx_preload_dVdd - preload the dVdd regulator during off state.
+ *
+ * This can help to reduce fluctuations in the dVdd voltage during startup
+ * at the cost of additional off state current draw.
+ *
+ * This API should only be called if dVdd startup issues are suspected.
+ *
+ * RETURNS: an appropriate -ERRNO error value on error, or zero for success.
+ */
+int pm8xxx_preload_dVdd(void)
+{
+ struct pm8xxx_misc_chip *chip;
+ unsigned long flags;
+ int rc = 0;
+
+ spin_lock_irqsave(&pm8xxx_misc_chips_lock, flags);
+
+ /* Loop over all attached PMICs and call specific functions for them. */
+ list_for_each_entry(chip, &pm8xxx_misc_chips, link) {
+ switch (chip->version) {
+ case PM8XXX_VERSION_8901:
+ rc = __pm8901_preload_dVdd(chip);
+ break;
+ default:
+ /* PMIC doesn't have preload_dVdd; do nothing. */
+ break;
+ }
+ if (rc) {
+ pr_err("preload_dVdd failed, rc=%d\n", rc);
+ break;
+ }
+ }
+
+ spin_unlock_irqrestore(&pm8xxx_misc_chips_lock, flags);
+
+ return rc;
+}
+EXPORT_SYMBOL_GPL(pm8xxx_preload_dVdd);
+
static int __devinit pm8xxx_misc_probe(struct platform_device *pdev)
{
const struct pm8xxx_misc_platform_data *pdata = pdev->dev.platform_data;
diff --git a/include/linux/mfd/pm8xxx/misc.h b/include/linux/mfd/pm8xxx/misc.h
index 32189b2..f9fc498 100644
--- a/include/linux/mfd/pm8xxx/misc.h
+++ b/include/linux/mfd/pm8xxx/misc.h
@@ -160,6 +160,18 @@
*/
int pm8xxx_stay_on(void);
+/**
+ * pm8xxx_preload_dVdd - preload the dVdd regulator during off state.
+ *
+ * This can help to reduce fluctuations in the dVdd voltage during startup
+ * at the cost of additional off state current draw.
+ *
+ * This API should only be called if dVdd startup issues are suspected.
+ *
+ * RETURNS: an appropriate -ERRNO error value on error, or zero for success.
+ */
+int pm8xxx_preload_dVdd(void);
+
#else
static inline int pm8xxx_reset_pwr_off(int reset)
@@ -196,6 +208,10 @@
{
return -ENODEV;
}
+static inline int pm8xxx_preload_dVdd(void)
+{
+ return -ENODEV;
+}
#endif
#endif