twl4030_charger: add software controlled linear charging mode.

Add a 'continuous' option for usb charging which enables
the "linear" charging mode of the twl4030.

Linear charging does a good job with not-so-reliable power sources.
Auto mode does not work well as it switches off when voltage drops
momentarily.  Care must be taken not to over-charge.

It was used with a bike hub dynamo since a year or so. In that case
there are automatically charging stops when the cyclist needs a break.

Original-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

diff --git a/Documentation/ABI/testing/sysfs-class-power-twl4030 b/Documentation/ABI/testing/sysfs-class-power-twl4030
index 40e0f919cbdeb440db37661834d583dfbe828b09..e8baa36aaa2b12db469764600cec67a4e8d81174 100644 (file)
--- a/Documentation/ABI/testing/sysfs-class-power-twl4030
+++ b/Documentation/ABI/testing/sysfs-class-power-twl4030
@@ -24,3 +24,12 @@ Description:
                "auto" - draw power as appropriate for detected
                         power source and battery status.
                "off"  - do not draw any power.
+               "continuous"
+                      - activate mode described as "linear" in
+                        TWL data sheets.  This uses whatever
+                        current is available and doesn't switch off
+                        when voltage drops.
+
+                        This is useful for unstable power sources
+                        such as bicycle dynamo, but care should
+                        be taken that battery is not over-charged.

diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c
index 6fa928ed3128b8b64e1d9652359b35a207f464ab..de5430deaf23989f492cee902fbe32a9ade165d9 100644 (file)
--- a/drivers/power/twl4030_charger.c
+++ b/drivers/power/twl4030_charger.c
@@ -24,6 +24,8 @@
 #include <linux/usb/otg.h>
 #include <linux/i2c/twl4030-madc.h>
 
+#define TWL4030_BCIMDEN                0x00
+#define TWL4030_BCIMDKEY       0x01
 #define TWL4030_BCIMSTATEC     0x02
 #define TWL4030_BCIICHG                0x08
 #define TWL4030_BCIVAC         0x0a
@@ -35,13 +37,16 @@
 #define TWL4030_BCIIREF1       0x27
 #define TWL4030_BCIIREF2       0x28
 #define TWL4030_BCIMFKEY       0x11
+#define TWL4030_BCIMFEN3       0x14
 #define TWL4030_BCIMFTH8       0x1d
 #define TWL4030_BCIMFTH9       0x1e
+#define TWL4030_BCIWDKEY       0x21
 
 #define TWL4030_BCIMFSTS1      0x01
 
 #define TWL4030_BCIAUTOWEN     BIT(5)
 #define TWL4030_CONFIG_DONE    BIT(4)
+#define TWL4030_CVENAC         BIT(2)
 #define TWL4030_BCIAUTOUSB     BIT(1)
 #define TWL4030_BCIAUTOAC      BIT(0)
 #define TWL4030_CGAIN          BIT(5)
@@ -112,12 +117,13 @@ struct twl4030_bci {
        int                     usb_mode; /* charging mode requested */
 #define        CHARGE_OFF      0
 #define        CHARGE_AUTO     1
+#define        CHARGE_LINEAR   2
 
        unsigned long           event;
 };
 
 /* strings for 'usb_mode' values */
-static char *modes[] = { "off", "auto" };
+static char *modes[] = { "off", "auto", "continuous" };
 
 /*
  * clear and set bits on an given register on a given module
@@ -404,16 +410,42 @@ static int twl4030_charger_enable_usb(struct twl4030_bci *bci, bool enable)
                        bci->usb_enabled = 1;
                }
 
-               /* forcing the field BCIAUTOUSB (BOOT_BCI[1]) to 1 */
-               ret = twl4030_clear_set_boot_bci(0, TWL4030_BCIAUTOUSB);
-               if (ret < 0)
-                       return ret;
+               if (bci->usb_mode == CHARGE_AUTO)
+                       /* forcing the field BCIAUTOUSB (BOOT_BCI[1]) to 1 */
+                       ret = twl4030_clear_set_boot_bci(0, TWL4030_BCIAUTOUSB);
 
                /* forcing USBFASTMCHG(BCIMFSTS4[2]) to 1 */
                ret = twl4030_clear_set(TWL_MODULE_MAIN_CHARGE, 0,
                        TWL4030_USBFASTMCHG, TWL4030_BCIMFSTS4);
+               if (bci->usb_mode == CHARGE_LINEAR) {
+                       twl4030_clear_set_boot_bci(TWL4030_BCIAUTOAC|TWL4030_CVENAC, 0);
+                       /* Watch dog key: WOVF acknowledge */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0x33,
+                                              TWL4030_BCIWDKEY);
+                       /* 0x24 + EKEY6: off mode */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0x2a,
+                                              TWL4030_BCIMDKEY);
+                       /* EKEY2: Linear charge: USB path */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0x26,
+                                              TWL4030_BCIMDKEY);
+                       /* WDKEY5: stop watchdog count */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0xf3,
+                                              TWL4030_BCIWDKEY);
+                       /* enable MFEN3 access */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0x9c,
+                                              TWL4030_BCIMFKEY);
+                        /* ICHGEOCEN - end-of-charge monitor (current < 80mA)
+                         *                      (charging continues)
+                         * ICHGLOWEN - current level monitor (charge continues)
+                         * don't monitor over-current or heat save
+                         */
+                       ret = twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0xf0,
+                                              TWL4030_BCIMFEN3);
+               }
        } else {
                ret = twl4030_clear_set_boot_bci(TWL4030_BCIAUTOUSB, 0);
+               ret |= twl_i2c_write_u8(TWL_MODULE_MAIN_CHARGE, 0x2a,
+                                       TWL4030_BCIMDKEY);
                if (bci->usb_enabled) {
                        pm_runtime_mark_last_busy(bci->transceiver->dev);
                        pm_runtime_put_autosuspend(bci->transceiver->dev);
@@ -652,6 +684,8 @@ twl4030_bci_mode_store(struct device *dev, struct device_attribute *attr,
                mode = 0;
        else if (sysfs_streq(buf, modes[1]))
                mode = 1;
+       else if (sysfs_streq(buf, modes[2]))
+               mode = 2;
        else
                return -EINVAL;
        twl4030_charger_enable_usb(bci, false);
@@ -750,6 +784,17 @@ static int twl4030_bci_get_property(struct power_supply *psy,
                is_charging = state & TWL4030_MSTATEC_USB;
        else
                is_charging = state & TWL4030_MSTATEC_AC;
+       if (!is_charging) {
+               u8 s;
+               twl4030_bci_read(TWL4030_BCIMDEN, &s);
+               if (psy->desc->type == POWER_SUPPLY_TYPE_USB)
+                       is_charging = s & 1;
+               else
+                       is_charging = s & 2;
+               if (is_charging)
+                       /* A little white lie */
+                       state = TWL4030_MSTATEC_QUICK1;
+       }
 
        switch (psp) {
        case POWER_SUPPLY_PROP_STATUS: