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>

1 files changed, 50 insertions, 5 deletions

diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c
index 6fa928ed3128..de5430deaf23 100644
--- 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: