pcf50633_charger: Enable periodic charging restart

The battery charger state machine switches into charging mode when
the battery voltage falls below 96% of a battery float voltage. But
the voltage drop in Li-ion batteries is marginal(1~2 %) till about
80% of its capacity - which means, after a BATFULL, charging won't
be restarted until 80%.

This work_struct function restarts charging at regular intervals to
make sure the battery doesn't discharge too much.

Signed-off-by: Balaji Rao <balajirrao@openmoko.org>
Cc: Andy Green <andy@openmoko.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

2 files changed, 73 insertions, 2 deletions

diff --git a/drivers/power/pcf50633-charger.c b/drivers/power/pcf50633-charger.c
index 41aec2acbb91..1fe1e851a8dd 100644
--- a/drivers/power/pcf50633-charger.c
+++ b/drivers/power/pcf50633-charger.c
@@ -36,6 +36,8 @@ struct pcf50633_mbc {
 
         struct power_supply usb;
         struct power_supply adapter;
+
+        struct delayed_work charging_restart_work;
 };
 
 int pcf50633_mbc_usb_curlim_set(struct pcf50633 *pcf, int ma)
@@ -43,6 +45,8 @@ int pcf50633_mbc_usb_curlim_set(struct pcf50633 *pcf, int ma)
         struct pcf50633_mbc *mbc = platform_get_drvdata(pcf->mbc_pdev);
         int ret = 0;
         u8 bits;
+        int charging_start = 1;
+        u8 mbcs2, chgmod;
 
         if (ma >= 1000)
                 bits = PCF50633_MBCC7_USB_1000mA;
@@ -50,8 +54,10 @@ int pcf50633_mbc_usb_curlim_set(struct pcf50633 *pcf, int ma)
                 bits = PCF50633_MBCC7_USB_500mA;
         else if (ma >= 100)
                 bits = PCF50633_MBCC7_USB_100mA;
-        else
+        else {
                 bits = PCF50633_MBCC7_USB_SUSPEND;
+                charging_start = 0;
+        }
 
         ret = pcf50633_reg_set_bit_mask(pcf, PCF50633_REG_MBCC7,
                                         PCF50633_MBCC7_USB_MASK, bits);
@@ -60,6 +66,22 @@ int pcf50633_mbc_usb_curlim_set(struct pcf50633 *pcf, int ma)
         else
                 dev_info(pcf->dev, "usb curlim to %d mA\n", ma);
 
+        /* Manual charging start */
+        mbcs2 = pcf50633_reg_read(pcf, PCF50633_REG_MBCS2);
+        chgmod = (mbcs2 & PCF50633_MBCS2_MBC_MASK);
+
+        /* If chgmod == BATFULL, setting chgena has no effect.
+         * We need to set resume instead.
+         */
+        if (chgmod != PCF50633_MBCS2_MBC_BAT_FULL)
+                pcf50633_reg_set_bit_mask(pcf, PCF50633_REG_MBCC1,
+                                PCF50633_MBCC1_CHGENA, PCF50633_MBCC1_CHGENA);
+        else
+                pcf50633_reg_set_bit_mask(pcf, PCF50633_REG_MBCC1,
+                                PCF50633_MBCC1_RESUME, PCF50633_MBCC1_RESUME);
+
+        mbc->usb_active = charging_start;
+
         power_supply_changed(&mbc->usb);
 
         return ret;
@@ -160,10 +182,44 @@ static struct attribute_group mbc_attr_group = {
         .attrs  = pcf50633_mbc_sysfs_entries,
 };
 
+/* MBC state machine switches into charging mode when the battery voltage
+ * falls below 96% of a battery float voltage. But the voltage drop in Li-ion
+ * batteries is marginal(1~2 %) till about 80% of its capacity - which means,
+ * after a BATFULL, charging won't be restarted until 80%.
+ *
+ * This work_struct function restarts charging at regular intervals to make
+ * sure we don't discharge too much
+ */
+
+static void pcf50633_mbc_charging_restart(struct work_struct *work)
+{
+        struct pcf50633_mbc *mbc;
+        u8 mbcs2, chgmod;
+
+        mbc = container_of(work, struct pcf50633_mbc,
+                                charging_restart_work.work);
+
+        mbcs2 = pcf50633_reg_read(mbc->pcf, PCF50633_REG_MBCS2);
+        chgmod = (mbcs2 & PCF50633_MBCS2_MBC_MASK);
+
+        if (chgmod != PCF50633_MBCS2_MBC_BAT_FULL)
+                return;
+
+        /* Restart charging */
+        pcf50633_reg_set_bit_mask(mbc->pcf, PCF50633_REG_MBCC1,
+                                PCF50633_MBCC1_RESUME, PCF50633_MBCC1_RESUME);
+        mbc->usb_active = 1;
+        power_supply_changed(&mbc->usb);
+
+        dev_info(mbc->pcf->dev, "Charging restarted\n");
+}
+
 static void
 pcf50633_mbc_irq_handler(int irq, void *data)
 {
         struct pcf50633_mbc *mbc = data;
+        int chg_restart_interval =
+                        mbc->pcf->pdata->charging_restart_interval;
 
         /* USB */
         if (irq == PCF50633_IRQ_USBINS) {
@@ -172,6 +228,7 @@ pcf50633_mbc_irq_handler(int irq, void *data)
                 mbc->usb_online = 0;
                 mbc->usb_active = 0;
                 pcf50633_mbc_usb_curlim_set(mbc->pcf, 0);
+                cancel_delayed_work_sync(&mbc->charging_restart_work);
         }
 
         /* Adapter */
@@ -186,7 +243,14 @@ pcf50633_mbc_irq_handler(int irq, void *data)
         if (irq == PCF50633_IRQ_BATFULL) {
                 mbc->usb_active = 0;
                 mbc->adapter_active = 0;
-        }
+
+                if (chg_restart_interval > 0)
+                        schedule_delayed_work(&mbc->charging_restart_work,
+                                                        chg_restart_interval);
+        } else if (irq == PCF50633_IRQ_USBLIMON)
+                mbc->usb_active = 0;
+        else if (irq == PCF50633_IRQ_USBLIMOFF)
+                mbc->usb_active = 1;
 
         power_supply_changed(&mbc->usb);
         power_supply_changed(&mbc->adapter);
@@ -303,6 +367,9 @@ static int __devinit pcf50633_mbc_probe(struct platform_device *pdev)
                 return ret;
         }
 
+        INIT_DELAYED_WORK(&mbc->charging_restart_work,
+                                pcf50633_mbc_charging_restart);
+
         ret = sysfs_create_group(&pdev->dev.kobj, &mbc_attr_group);
         if (ret)
                 dev_err(mbc->pcf->dev, "failed to create sysfs entries\n");
@@ -328,6 +395,8 @@ static int __devexit pcf50633_mbc_remove(struct platform_device *pdev)
         power_supply_unregister(&mbc->usb);
         power_supply_unregister(&mbc->adapter);
 
+        cancel_delayed_work_sync(&mbc->charging_restart_work);
+
         kfree(mbc);
 
         return 0;
diff --git a/include/linux/mfd/pcf50633/core.h b/include/linux/mfd/pcf50633/core.h
index 4455b212d75a..c8f51c3c0a72 100644
--- a/include/linux/mfd/pcf50633/core.h
+++ b/include/linux/mfd/pcf50633/core.h
@@ -29,6 +29,8 @@ struct pcf50633_platform_data {
         char **batteries;
         int num_batteries;
 
+        int charging_restart_interval;
+
         /* Callbacks */
         void (*probe_done)(struct pcf50633 *);
         void (*mbc_event_callback)(struct pcf50633 *, int);