[PATCH v2 0/6] Provides bug fixes for rtc-mcp795.c

[PATCH v2 0/6] Provides bug fixes for rtc-mcp795.c

[Emil Bartczak]

This patchset provides 4 bug fixes (patch 1, 2, 3, 4), one 
improvement (patch 5) and whitespace, indention errors fixes 
(patch 6) in the file driver/rtc/rtc-mcp795.c.
Please review the changes and consider to apply them to the 
main kernel tree.

Changes from v1:
- Introduced SoB to all patches.
- Patch which switches to bcd2bin/bin2bcd became as first now, 
  it also solved the shift problem presented in the previous patch 1.
- Added restoring EXTOSC bit to its previous value.
- All whitespace and indention fixes moved to the new patch 6.
- Added new patch which replaces all bitmask values with the 
  BIT(x) macro.

Emil Bartczak (6):
  rtc: mcp795: use bcd2bin/bin2bcd.
  rtc: mcp795: fix bitmask value for leap year (LP).
  rtc: mcp795: fix time range difference between linux and RTC chip.
  rtc: mcp795: fix month write resetting date to 1.
  rtc: mcp795: Prefer using the BIT() macro.
  rtc: mcp795: Fix whitespace and indentation.

 drivers/rtc/rtc-mcp795.c | 122 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 100 insertions(+), 22 deletions(-)

-- 
2.7.4

[PATCH v2 1/6] rtc: mcp795: use bcd2bin/bin2bcd.

[Emil Bartczak]

Change rtc-mcp795.c to use the bcd2bin/bin2bcd functions.
This change fixes the wrong conversion of month value
from binary to BCD (missing right shift operation for 10 month).

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 4021fd0..0389ee0 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -21,6 +21,7 @@
 #include <linux/spi/spi.h>
 #include <linux/rtc.h>
 #include <linux/of.h>
+#include <linux/bcd.h>
 
 /* MCP795 Instructions, see datasheet table 3-1 */
 #define MCP795_EEREAD	0x03
@@ -104,16 +105,16 @@ static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
 	if (ret)
 		return ret;
 
-	data[0] = (data[0] & 0x80) | ((tim->tm_sec / 10) << 4) | (tim->tm_sec % 10);
-	data[1] = (data[1] & 0x80) | ((tim->tm_min / 10) << 4) | (tim->tm_min % 10);
-	data[2] = ((tim->tm_hour / 10) << 4) | (tim->tm_hour % 10);
-	data[4] = ((tim->tm_mday / 10) << 4) | ((tim->tm_mday) % 10);
-	data[5] = (data[5] & 0x10) | (tim->tm_mon / 10) | (tim->tm_mon % 10);
+	data[0] = (data[0] & 0x80) | bin2bcd(tim->tm_sec);
+	data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min);
+	data[2] = bin2bcd(tim->tm_hour);
+	data[4] = bin2bcd(tim->tm_mday);
+	data[5] = (data[5] & 0x10) | bin2bcd(tim->tm_mon);
 
 	if (tim->tm_year > 100)
 		tim->tm_year -= 100;
 
-	data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10);
+	data[6] = bin2bcd(tim->tm_year);
 
 	ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
 
@@ -137,12 +138,12 @@ static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
 	if (ret)
 		return ret;
 
-	tim->tm_sec		= ((data[0] & 0x70) >> 4) * 10 + (data[0] & 0x0f);
-	tim->tm_min		= ((data[1] & 0x70) >> 4) * 10 + (data[1] & 0x0f);
-	tim->tm_hour	= ((data[2] & 0x30) >> 4) * 10 + (data[2] & 0x0f);
-	tim->tm_mday	= ((data[4] & 0x30) >> 4) * 10 + (data[4] & 0x0f);
-	tim->tm_mon		= ((data[5] & 0x10) >> 4) * 10 + (data[5] & 0x0f);
-	tim->tm_year	= ((data[6] & 0xf0) >> 4) * 10 + (data[6] & 0x0f) + 100; /* Assume we are in 20xx */
+	tim->tm_sec	= bcd2bin(data[0] & 0x7F);
+	tim->tm_min	= bcd2bin(data[1] & 0x7F);
+	tim->tm_hour	= bcd2bin(data[2] & 0x3F);
+	tim->tm_mday	= bcd2bin(data[4] & 0x3F);
+	tim->tm_mon	= bcd2bin(data[5] & 0x1F);
+	tim->tm_year	= bcd2bin(data[6]) + 100; /* Assume we are in 20xx */
 
 	dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
 				tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
-- 
2.7.4

[PATCH v2 2/6] rtc: mcp795: fix bitmask value for leap year (LP).

[Emil Bartczak]

According the datasheet the leap year is a fifth bit in month register.

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 0389ee0..5fbdb4c 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -40,6 +40,7 @@
 
 #define MCP795_ST_BIT	0x80
 #define MCP795_24_BIT	0x40
+#define MCP795_LP_BIT	BIT(5)
 
 static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
 {
@@ -109,7 +110,7 @@ static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
 	data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min);
 	data[2] = bin2bcd(tim->tm_hour);
 	data[4] = bin2bcd(tim->tm_mday);
-	data[5] = (data[5] & 0x10) | bin2bcd(tim->tm_mon);
+	data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon);
 
 	if (tim->tm_year > 100)
 		tim->tm_year -= 100;
-- 
2.7.4

[PATCH v2 3/6] rtc: mcp795: fix time range difference between linux and RTC chip.

[Emil Bartczak]

In linux rtc_time struct, tm_mon range is 0~11, while in RTC HW REG,
month range is 1~12. This patch adjusts difference of them.

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 5fbdb4c..4618f4f 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -110,7 +110,7 @@ static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
 	data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min);
 	data[2] = bin2bcd(tim->tm_hour);
 	data[4] = bin2bcd(tim->tm_mday);
-	data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon);
+	data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1);
 
 	if (tim->tm_year > 100)
 		tim->tm_year -= 100;
@@ -143,7 +143,7 @@ static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
 	tim->tm_min	= bcd2bin(data[1] & 0x7F);
 	tim->tm_hour	= bcd2bin(data[2] & 0x3F);
 	tim->tm_mday	= bcd2bin(data[4] & 0x3F);
-	tim->tm_mon	= bcd2bin(data[5] & 0x1F);
+	tim->tm_mon	= bcd2bin(data[5] & 0x1F) - 1;
 	tim->tm_year	= bcd2bin(data[6]) + 100; /* Assume we are in 20xx */
 
 	dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
-- 
2.7.4

[PATCH v2 4/6] rtc: mcp795: fix month write resetting date to 1.

[Emil Bartczak]

According to Microchip errata some combinations of date and month
values may result in the date being reset to 1, even if the date
is also written with the month (for example 31-07 or 31-08).
As a workaround avoid writing date and month values within the same
Write command. Instead, terminate the Write command after loading
the date and begin a new command to write the month. In addition,
disable the oscillator before loading the new values. This is done
by ensuring both the ST and EXTOSC bits are cleared and waiting for
the OSCON bit to clear.

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 86 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 81 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 4618f4f..89b0ffa 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -22,6 +22,7 @@
 #include <linux/rtc.h>
 #include <linux/of.h>
 #include <linux/bcd.h>
+#include <linux/delay.h>
 
 /* MCP795 Instructions, see datasheet table 3-1 */
 #define MCP795_EEREAD	0x03
@@ -38,9 +39,17 @@
 #define MCP795_CLRWDT	0x44
 #define MCP795_CLRRAM	0x54
 
+/* MCP795 RTCC registers, see datasheet table 4-1 */
+#define MCP795_REG_SECONDS	0x01
+#define MCP795_REG_DAY		0x04
+#define MCP795_REG_MONTH	0x06
+#define MCP795_REG_CONTROL	0x08
+
 #define MCP795_ST_BIT	0x80
 #define MCP795_24_BIT	0x40
 #define MCP795_LP_BIT	BIT(5)
+#define MCP795_EXTOSC_BIT	BIT(3)
+#define MCP795_OSCON_BIT	BIT(5)
 
 static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
 {
@@ -95,13 +104,65 @@ static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
 	return ret;
 }
 
+static int mcp795_stop_oscillator(struct device *dev, bool *extosc)
+{
+	int retries = 5;
+	int ret;
+	u8 data;
+
+	ret = mcp795_rtcc_set_bits(dev, MCP795_REG_SECONDS, MCP795_ST_BIT, 0);
+	if (ret)
+		return ret;
+	ret = mcp795_rtcc_read(dev, MCP795_REG_CONTROL, &data, 1);
+	if (ret)
+		return ret;
+	*extosc = !!(data & MCP795_EXTOSC_BIT);
+	ret = mcp795_rtcc_set_bits(
+				dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, 0);
+	if (ret)
+		return ret;
+	/* wait for the OSCON bit to clear */
+	do {
+		usleep_range(700, 800);
+		ret = mcp795_rtcc_read(dev, MCP795_REG_DAY, &data, 1);
+		if (ret)
+			break;
+		if (!(data & MCP795_OSCON_BIT))
+			break;
+
+	} while (--retries);
+
+	return !retries ? -EIO : ret;
+}
+
+static int mcp795_start_oscillator(struct device *dev, bool *extosc)
+{
+	if (extosc) {
+		u8 data = *extosc ? MCP795_EXTOSC_BIT : 0;
+		int ret;
+
+		ret = mcp795_rtcc_set_bits(
+			dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, data);
+		if (ret)
+			return ret;
+	}
+	return mcp795_rtcc_set_bits(
+			dev, MCP795_REG_SECONDS, MCP795_ST_BIT, MCP795_ST_BIT);
+}
+
 static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
 {
 	int ret;
 	u8 data[7];
+	bool extosc;
+
+	/* Stop RTC and store current value of EXTOSC bit */
+	ret = mcp795_stop_oscillator(dev, &extosc);
+	if (ret)
+		return ret;
 
 	/* Read first, so we can leave config bits untouched */
-	ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
+	ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
 
 	if (ret)
 		return ret;
@@ -117,8 +178,23 @@ static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
 
 	data[6] = bin2bcd(tim->tm_year);
 
-	ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
+	/* Always write the date and month using a separate Write command.
+	 * This is a workaround for a know silicon issue that some combinations
+	 * of date and month values may result in the date being reset to 1.
+	 */
+	ret = mcp795_rtcc_write(dev, MCP795_REG_SECONDS, data, 5);
+	if (ret)
+		return ret;
+
+	ret = mcp795_rtcc_write(dev, MCP795_REG_MONTH, &data[5], 2);
+	if (ret)
+		return ret;
 
+	/* Start back RTC and restore previous value of EXTOSC bit.
+	 * There is no need to clear EXTOSC bit when the previous value was 0
+	 * because it was already cleared when stopping the RTC oscillator.
+	 */
+	ret = mcp795_start_oscillator(dev, extosc ? &extosc : NULL);
 	if (ret)
 		return ret;
 
@@ -134,7 +210,7 @@ static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
 	int ret;
 	u8 data[7];
 
-	ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
+	ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
 
 	if (ret)
 		return ret;
@@ -171,8 +247,8 @@ static int mcp795_probe(struct spi_device *spi)
 		return ret;
 	}
 
-	/* Start the oscillator */
-	mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT);
+	/* Start the oscillator but don't set the value of EXTOSC bit */
+	mcp795_start_oscillator(&spi->dev, NULL);
 	/* Clear the 12 hour mode flag*/
 	mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
 
-- 
2.7.4

[PATCH v2 5/6] rtc: mcp795: Prefer using the BIT() macro.

[Emil Bartczak]

This patch doesn't change the code but replaces all bitmask values
with the BIT(x) macro.

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 89b0ffa..8ed55f6 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -45,8 +45,8 @@
 #define MCP795_REG_MONTH	0x06
 #define MCP795_REG_CONTROL	0x08
 
-#define MCP795_ST_BIT	0x80
-#define MCP795_24_BIT	0x40
+#define MCP795_ST_BIT	BIT(7)
+#define MCP795_24_BIT	BIT(6)
 #define MCP795_LP_BIT	BIT(5)
 #define MCP795_EXTOSC_BIT	BIT(3)
 #define MCP795_OSCON_BIT	BIT(5)
-- 
2.7.4

[PATCH v2 6/6] rtc: mcp795: Fix whitespace and indentation.

[Emil Bartczak]

Fix whitespace and indentation errors and the following
checkpatch warnings:
- line 15: Block comments use a trailing */ on a separate line
- line 256: Line over 80 characters
No code change.

Signed-off-by: Emil Bartczak <emilbart@gmail.com>
---
 drivers/rtc/rtc-mcp795.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
index 8ed55f6..ce75e42 100644
--- a/drivers/rtc/rtc-mcp795.c
+++ b/drivers/rtc/rtc-mcp795.c
@@ -12,7 +12,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- * */
+ */
 
 #include <linux/module.h>
 #include <linux/kernel.h>
@@ -31,7 +31,7 @@
 #define MCP795_EEWREN	0x06
 #define MCP795_SRREAD	0x05
 #define MCP795_SRWRITE	0x01
-#define MCP795_READ		0x13
+#define MCP795_READ	0x13
 #define MCP795_WRITE	0x12
 #define MCP795_UNLOCK	0x14
 #define MCP795_IDWRITE	0x32
@@ -45,9 +45,9 @@
 #define MCP795_REG_MONTH	0x06
 #define MCP795_REG_CONTROL	0x08
 
-#define MCP795_ST_BIT	BIT(7)
-#define MCP795_24_BIT	BIT(6)
-#define MCP795_LP_BIT	BIT(5)
+#define MCP795_ST_BIT		BIT(7)
+#define MCP795_24_BIT		BIT(6)
+#define MCP795_LP_BIT		BIT(5)
 #define MCP795_EXTOSC_BIT	BIT(3)
 #define MCP795_OSCON_BIT	BIT(5)
 
@@ -253,7 +253,7 @@ static int mcp795_probe(struct spi_device *spi)
 	mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
 
 	rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
-								&mcp795_rtc_ops, THIS_MODULE);
+					&mcp795_rtc_ops, THIS_MODULE);
 	if (IS_ERR(rtc))
 		return PTR_ERR(rtc);
 
-- 
2.7.4

Re: [PATCH v2 0/6] Provides bug fixes for rtc-mcp795.c

[Alexandre Belloni]

On 08/12/2016 at 00:27:36 +0100, Emil Bartczak wrote :
> This patchset provides 4 bug fixes (patch 1, 2, 3, 4), one 
> improvement (patch 5) and whitespace, indention errors fixes 
> (patch 6) in the file driver/rtc/rtc-mcp795.c.
> Please review the changes and consider to apply them to the 
> main kernel tree.
> 
> Changes from v1:
> - Introduced SoB to all patches.
> - Patch which switches to bcd2bin/bin2bcd became as first now, 
>   it also solved the shift problem presented in the previous patch 1.
> - Added restoring EXTOSC bit to its previous value.
> - All whitespace and indention fixes moved to the new patch 6.
> - Added new patch which replaces all bitmask values with the 
>   BIT(x) macro.
> 
> Emil Bartczak (6):
>   rtc: mcp795: use bcd2bin/bin2bcd.
>   rtc: mcp795: fix bitmask value for leap year (LP).
>   rtc: mcp795: fix time range difference between linux and RTC chip.
>   rtc: mcp795: fix month write resetting date to 1.
>   rtc: mcp795: Prefer using the BIT() macro.
>   rtc: mcp795: Fix whitespace and indentation.
> 
>  drivers/rtc/rtc-mcp795.c | 122 ++++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 100 insertions(+), 22 deletions(-)
> 

All applied, thanks!

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com