[PATCH v6 22/23] rtc: Add driver for Maxim 77802 PMIC Real-Time-Clock

Hello Krzysztof,

On 07/04/2014 03:11 PM, Krzysztof Kozlowski wrote:

On pi?, 2014-07-04 at 14:52 +0200, Javier Martinez Canillas wrote:

quoted

Hello Krzysztof,

Thanks a lot for your feedback.

On 07/04/2014 01:56 PM, Krzysztof Kozlowski wrote:

quoted

On pi?, 2014-07-04 at 11:55 +0200, Javier Martinez Canillas wrote:

quoted

The MAX7802 PMIC has a Real-Time-Clock (RTC) with two alarms.
This patch adds support for the RTC and is based on a driver
added by Simon Glass to the Chrome OS kernel 3.8 tree.

Signed-off-by: Javier Martinez Canillas <redacted>
---

Changes since v5: None

Changes since v4: None

Changes since v3: None
---
 drivers/rtc/Kconfig        |  10 +
 drivers/rtc/Makefile       |   1 +
 drivers/rtc/rtc-max77802.c | 637 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 648 insertions(+)
 create mode 100644 drivers/rtc/rtc-max77802.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index a672dd1..243ac72 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig

@@ -288,6 +288,16 @@ config RTC_DRV_MAX77686
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-max77686.
 
+config RTC_DRV_MAX77802
+	tristate "Maxim 77802 RTC"
+	depends on MFD_MAX77686
+	help
+	  If you say yes here you will get support for the
+	  RTC of Maxim MAX77802 PMIC.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-max77802.
+
 config RTC_DRV_RS5C372
 	tristate "Ricoh R2025S/D, RS5C372A/B, RV5C386, RV5C387A"
 	help

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 70347d0..247de78 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile

@@ -81,6 +81,7 @@ obj-$(CONFIG_RTC_DRV_MAX8998)	+= rtc-max8998.o
 obj-$(CONFIG_RTC_DRV_MAX8997)	+= rtc-max8997.o
 obj-$(CONFIG_RTC_DRV_MAX6902)	+= rtc-max6902.o
 obj-$(CONFIG_RTC_DRV_MAX77686)	+= rtc-max77686.o
+obj-$(CONFIG_RTC_DRV_MAX77802)  += rtc-max77802.o
 obj-$(CONFIG_RTC_DRV_MC13XXX)	+= rtc-mc13xxx.o
 obj-$(CONFIG_RTC_DRV_MCP795)	+= rtc-mcp795.o
 obj-$(CONFIG_RTC_DRV_MSM6242)	+= rtc-msm6242.o

diff --git a/drivers/rtc/rtc-max77802.c b/drivers/rtc/rtc-max77802.c
new file mode 100644
index 0000000..2f4fc2e
--- /dev/null
+++ b/drivers/rtc/rtc-max77802.c

@@ -0,0 +1,637 @@
+/*
+ * RTC driver for Maxim MAX77802
+ *
+ * Copyright (C) 2013 Google, Inc
+ *
+ * Copyright (C) 2012 Samsung Electronics Co.Ltd
+ *
+ *  based on rtc-max8997.c
+ *
+ *  This program is free software; you can redistribute  it and/or modify it
+ *  under  the terms of  the GNU General  Public License as published by the
+ *  Free Software Foundation;  either version 2 of the  License, or (at your
+ *  option) any later version.
+ *
+ */
+
+#include <linux/slab.h>
+#include <linux/rtc.h>
+#include <linux/delay.h>
+#include <linux/mutex.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/max77686-private.h>
+#include <linux/irqdomain.h>
+#include <linux/regmap.h>
+
+/* RTC Control Register */
+#define BCD_EN_SHIFT			0
+#define BCD_EN_MASK			(1 << BCD_EN_SHIFT)
+#define MODEL24_SHIFT			1
+#define MODEL24_MASK			(1 << MODEL24_SHIFT)
+/* RTC Update Register1 */
+#define RTC_UDR_SHIFT			0
+#define RTC_UDR_MASK			(1 << RTC_UDR_SHIFT)
+#define RTC_RBUDR_SHIFT			4
+#define RTC_RBUDR_MASK			(1 << RTC_RBUDR_SHIFT)
+/* WTSR and SMPL Register */
+#define WTSRT_SHIFT			0
+#define SMPLT_SHIFT			2
+#define WTSR_EN_SHIFT			6
+#define SMPL_EN_SHIFT			7
+#define WTSRT_MASK			(3 << WTSRT_SHIFT)
+#define SMPLT_MASK			(3 << SMPLT_SHIFT)
+#define WTSR_EN_MASK			(1 << WTSR_EN_SHIFT)
+#define SMPL_EN_MASK			(1 << SMPL_EN_SHIFT)
+/* RTC Hour register */
+#define HOUR_PM_SHIFT			6
+#define HOUR_PM_MASK			(1 << HOUR_PM_SHIFT)
+/* RTC Alarm Enable */
+#define ALARM_ENABLE_SHIFT		7
+#define ALARM_ENABLE_MASK		(1 << ALARM_ENABLE_SHIFT)
+
+/* For the RTCAE1 register, we write this value to enable the alarm */
+#define ALARM_ENABLE_VALUE		0x77
+
+#define MAX77802_RTC_UPDATE_DELAY_US	200
+#undef MAX77802_RTC_WTSR_SMPL

Hmmm... I am not sure what is the purpose of this undef. It disables
some functions below. I saw same code in 77686 RTC driver but this does
not help me :).

If this is on purpose can you add a comment explaining the
purpose/cause?

This is a left over from when a combined 77686/802 driver was attempted since as
you said the 77686 RTC driver does the same.

I just checked MAX77802 data sheet and the MAX77802_RTC_WTSR_SMPL register is to
control the SMPL (Sudden Momentary Power Loss) and WTSR (Watchdog Timeout and
Software Resets) features.

Now, I wanted to figure out why the 77686 driver unset that register and have
those conditionals but git blame shows me that this was already in the original
commit that added the driver: fca1dd03 ("rtc: max77686: add Maxim 77686 driver").

Also, I see that the MAX8997 driver (drivers/rtc/rtc-max8997.c) also has a
similar register but actually uses it and doesn't have the conditionals if is
disabled. But this driver has two module parameters to control if these features
are enabled or not (wtsr_en and smpl_en).

If these two features have been disabled since the max77686 driver was merged
then I guess that the dead code should be removed from that driver as well? Or
do you have more hints about why it has been disabled?

If the max77802 driver in current form works fine for your setup then I
think these functions can be removed completely. It should not harm
since this is dead code anyway and it will simplify the driver.

Agreed, I'll just remove it.

I think the same applies to max77686 (especially that as you said - this
is dead since beginning). Just remove it in separate patch.

Ok, I'll add that as a separate cleanup patch in the next version of the series
as well.

Best regards,
Krzysztof

Best regards,
Javier