drivers/rtc/rtc-palmas.c: support for backup battery charging

Palmas series device like TPS65913, TPS80036 supports the backup battery
for powering the RTC when no other energy source is available.

The backup battery is optional, connected to the VBACKUP pin, and can be
nonrechargeable or rechargeable.  The rechargeable battery can be charged
from the system supply using the backup battery charger.

Add support for enabling charging of this backup battery.  Also add the DT
binding document and the new properties to have this support.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Acked-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-palmas.c b/drivers/rtc/rtc-palmas.c
index a1fecc8d97fc..fffb7d3449d7 100644
--- a/drivers/rtc/rtc-palmas.c
+++ b/drivers/rtc/rtc-palmas.c
@@ -238,6 +238,15 @@ static int palmas_rtc_probe(struct platform_device *pdev)
         struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
         struct palmas_rtc *palmas_rtc = NULL;
         int ret;
+        bool enable_bb_charging = false;
+        bool high_bb_charging;
+
+        if (pdev->dev.of_node) {
+                enable_bb_charging = of_property_read_bool(pdev->dev.of_node,
+                                        "ti,backup-battery-chargeable");
+                high_bb_charging = of_property_read_bool(pdev->dev.of_node,
+                                        "ti,backup-battery-charge-high-current");
+        }
 
         palmas_rtc = devm_kzalloc(&pdev->dev, sizeof(struct palmas_rtc),
                         GFP_KERNEL);
@@ -254,6 +263,32 @@ static int palmas_rtc_probe(struct platform_device *pdev)
         palmas_rtc->dev = &pdev->dev;
         platform_set_drvdata(pdev, palmas_rtc);
 
+        if (enable_bb_charging) {
+                unsigned reg = PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG;
+
+                if (high_bb_charging)
+                        reg = 0;
+
+                ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+                        PALMAS_BACKUP_BATTERY_CTRL,
+                        PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG, reg);
+                if (ret < 0) {
+                        dev_err(&pdev->dev,
+                                "BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+                        return ret;
+                }
+
+                ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+                        PALMAS_BACKUP_BATTERY_CTRL,
+                        PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN,
+                        PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN);
+                if (ret < 0) {
+                        dev_err(&pdev->dev,
+                                "BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+                        return ret;
+                }
+        }
+
         /* Start RTC */
         ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
                         PALMAS_RTC_CTRL_REG_STOP_RTC,