mfd: Support LP3974 RTC

The first releases of LP3974 have a large delay in RTC registers,
which requires 2 seconds of delay after writing to a rtc register
(recommended by National Semiconductor's engineers)
before reading it.

If "rtc_delay" field of the platform data is true, the rtc driver
assumes that such delays are required. Although we have not seen
LP3974s without requiring such delays, we assume that such LP3974s
will be released soon (or they have done so already) and they are
supported by "lp3974" without setting "rtc_delay" at the platform
data.

This patch adds delays with msleep when writing values to RTC registers
if the platform data has rtc_delay set.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

1 files changed, 49 insertions, 5 deletions

diff --git a/drivers/rtc/rtc-max8998.c b/drivers/rtc/rtc-max8998.c
index f22dee35f330..3f7bc6b9fefa 100644
--- a/drivers/rtc/rtc-max8998.c
+++ b/drivers/rtc/rtc-max8998.c
@@ -20,6 +20,7 @@
 #include <linux/platform_device.h>
 #include <linux/mfd/max8998.h>
 #include <linux/mfd/max8998-private.h>
+#include <linux/delay.h>
 
 #define MAX8998_RTC_SEC                 0x00
 #define MAX8998_RTC_MIN                 0x01
@@ -73,6 +74,7 @@ struct max8998_rtc_info {
         struct i2c_client       *rtc;
         struct rtc_device       *rtc_dev;
         int irq;
+        bool lp3974_bug_workaround;
 };
 
 static void max8998_data_to_tm(u8 *data, struct rtc_time *tm)
@@ -124,10 +126,16 @@ static int max8998_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
         struct max8998_rtc_info *info = dev_get_drvdata(dev);
         u8 data[8];
+        int ret;
 
         max8998_tm_to_data(tm, data);
 
-        return max8998_bulk_write(info->rtc, MAX8998_RTC_SEC, 8, data);
+        ret = max8998_bulk_write(info->rtc, MAX8998_RTC_SEC, 8, data);
+
+        if (info->lp3974_bug_workaround)
+                msleep(2000);
+
+        return ret;
 }
 
 static int max8998_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
@@ -163,12 +171,29 @@ static int max8998_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 
 static int max8998_rtc_stop_alarm(struct max8998_rtc_info *info)
 {
-        return max8998_write_reg(info->rtc, MAX8998_ALARM0_CONF, 0);
+        int ret = max8998_write_reg(info->rtc, MAX8998_ALARM0_CONF, 0);
+
+        if (info->lp3974_bug_workaround)
+                msleep(2000);
+
+        return ret;
 }
 
 static int max8998_rtc_start_alarm(struct max8998_rtc_info *info)
 {
-        return max8998_write_reg(info->rtc, MAX8998_ALARM0_CONF, 0x77);
+        int ret;
+        u8 alarm0_conf = 0x77;
+
+        /* LP3974 with delay bug chips has rtc alarm bugs with "MONTH" field */
+        if (info->lp3974_bug_workaround)
+                alarm0_conf = 0x57;
+
+        ret = max8998_write_reg(info->rtc, MAX8998_ALARM0_CONF, alarm0_conf);
+
+        if (info->lp3974_bug_workaround)
+                msleep(2000);
+
+        return ret;
 }
 
 static int max8998_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
@@ -187,10 +212,13 @@ static int max8998_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
         if (ret < 0)
                 return ret;
 
+        if (info->lp3974_bug_workaround)
+                msleep(2000);
+
         if (alrm->enabled)
-                return max8998_rtc_start_alarm(info);
+                ret = max8998_rtc_start_alarm(info);
 
-        return 0;
+        return ret;
 }
 
 static int max8998_rtc_alarm_irq_enable(struct device *dev,
@@ -224,6 +252,7 @@ static const struct rtc_class_ops max8998_rtc_ops = {
 static int __devinit max8998_rtc_probe(struct platform_device *pdev)
 {
         struct max8998_dev *max8998 = dev_get_drvdata(pdev->dev.parent);
+        struct max8998_platform_data *pdata = dev_get_platdata(max8998->dev);
         struct max8998_rtc_info *info;
         int ret;
 
@@ -249,10 +278,18 @@ static int __devinit max8998_rtc_probe(struct platform_device *pdev)
 
         ret = request_threaded_irq(info->irq, NULL, max8998_rtc_alarm_irq, 0,
                         "rtc-alarm0", info);
+
         if (ret < 0)
                 dev_err(&pdev->dev, "Failed to request alarm IRQ: %d: %d\n",
                         info->irq, ret);
 
+        dev_info(&pdev->dev, "RTC CHIP NAME: %s\n", pdev->id_entry->name);
+        if (pdata->rtc_delay) {
+                info->lp3974_bug_workaround = true;
+                dev_warn(&pdev->dev, "LP3974 with RTC REGERR option."
+                                " RTC updates will be extremely slow.\n");
+        }
+
         return 0;
 
 out_rtc:
@@ -273,6 +310,12 @@ static int __devexit max8998_rtc_remove(struct platform_device *pdev)
         return 0;
 }
 
+static const struct platform_device_id max8998_rtc_id[] = {
+        { "max8998-rtc", TYPE_MAX8998 },
+        { "lp3974-rtc", TYPE_LP3974 },
+        { }
+};
+
 static struct platform_driver max8998_rtc_driver = {
         .driver         = {
                 .name   = "max8998-rtc",
@@ -280,6 +323,7 @@ static struct platform_driver max8998_rtc_driver = {
         },
         .probe          = max8998_rtc_probe,
         .remove         = __devexit_p(max8998_rtc_remove),
+        .id_table       = max8998_rtc_id,
 };
 
 static int __init max8998_rtc_init(void)