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Date: Tue, 6 May 2014 19:13:18 +0200
From: atx@....name
To: a.zummo@...ertech.it
Cc: linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com
Subject: [PATCH] rtc: Add support for Microchip MCP795
Adds driver for SPI RTC Microchip MCP795. Does only support saving/loading time from the chip (i. e. no alarms/power events/ID).
Signed-off-by: Josef Gajdusek <atx@....name>
---
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 2e565f8..bcffe07 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -650,6 +650,14 @@ config RTC_DRV_RX4581
This driver can also be built as a module. If so the module
will be called rtc-rx4581.
+config RTC_DRV_MCP795
+ tristate "Microchip MCP795"
+ help
+ If you say yes here you will get support for the Microchip MCP795.
+
+ This driver can also be built as a module. If so the module
+ will be called rtc-mcp795.
+
endif # SPI_MASTER
comment "Platform RTC drivers"
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 40a0991..816ad37 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -80,6 +80,7 @@ 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_MC13XXX) += rtc-mc13xxx.o
+obj-$(CONFIG_RTC_DRV_MCP795) += rtc-mcp795.o
obj-$(CONFIG_RTC_DRV_MSM6242) += rtc-msm6242.o
obj-$(CONFIG_RTC_DRV_MPC5121) += rtc-mpc5121.o
obj-$(CONFIG_RTC_DRV_MV) += rtc-mv.o
diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c
new file mode 100644
index 0000000..34295bf
--- /dev/null
+++ b/drivers/rtc/rtc-mcp795.c
@@ -0,0 +1,199 @@
+/*
+ * SPI Driver for Microchip MCP795 RTC
+ *
+ * Copyright (C) Josef Gajdusek <atx@....name>
+ *
+ * based on other Linux RTC drivers
+ *
+ * Device datasheet:
+ * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * 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>
+#include <linux/device.h>
+#include <linux/printk.h>
+#include <linux/spi/spi.h>
+#include <linux/rtc.h>
+
+/* MCP795 Instructions, see datasheet table 3-1 */
+#define MCP795_EEREAD 0x03
+#define MCP795_EEWRITE 0x02
+#define MCP795_EEWRDI 0x04
+#define MCP795_EEWREN 0x06
+#define MCP795_SRREAD 0x05
+#define MCP795_SRWRITE 0x01
+#define MCP795_READ 0x13
+#define MCP795_WRITE 0x12
+#define MCP795_UNLOCK 0x14
+#define MCP795_IDWRITE 0x32
+#define MCP795_IDREAD 0x33
+#define MCP795_CLRWDT 0x44
+#define MCP795_CLRRAM 0x54
+
+#define MCP795_ST_BIT 0x80
+#define MCP795_24_BIT 0x40
+
+static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
+{
+ struct spi_device *spi = to_spi_device(dev);
+ int ret;
+ u8 tx[2];
+
+ tx[0] = MCP795_READ;
+ tx[1] = addr;
+ ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
+
+ if (ret)
+ dev_err(dev, "Failed reading %d bytes from address %x.\n",
+ count, addr);
+
+ return ret;
+}
+
+static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
+{
+ struct spi_device *spi = to_spi_device(dev);
+ int ret;
+ u8 tx[2 + count];
+
+ tx[0] = MCP795_WRITE;
+ tx[1] = addr;
+ memcpy(&tx[2], data, count);
+
+ ret = spi_write(spi, tx, 2 + count);
+
+ if (ret)
+ dev_err(dev, "Failed to write %d bytes to address %x.\n",
+ count, addr);
+
+ return ret;
+}
+
+static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
+{
+ int ret;
+ u8 tmp;
+
+ ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
+ if (ret)
+ return ret;
+
+ if ((tmp & mask) != state) {
+ tmp = (tmp & ~mask) | state;
+ ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
+ }
+
+ return ret;
+}
+
+static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
+{
+ int ret;
+ u8 data[7];
+
+ /* Read first, so we can leave config bits untouched */
+ ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
+
+ 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);
+
+ if (tim->tm_year > 100)
+ tim->tm_year -= 100;
+
+ data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10);
+
+ ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
+
+ if (ret)
+ return ret;
+
+ dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
+ tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
+ tim->tm_hour, tim->tm_min, tim->tm_sec);
+
+ return 0;
+}
+
+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));
+
+ 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 */
+
+ dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
+ tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
+ tim->tm_hour, tim->tm_min, tim->tm_sec);
+
+ return rtc_valid_tm(tim);
+}
+
+static struct rtc_class_ops mcp795_rtc_ops = {
+ .read_time = mcp795_read_time,
+ .set_time = mcp795_set_time
+};
+
+static int mcp795_probe(struct spi_device *spi)
+{
+ struct rtc_device *rtc;
+ int ret;
+
+ spi->mode = SPI_MODE_0;
+ spi->bits_per_word = 8;
+ ret = spi_setup(spi);
+ if (ret) {
+ dev_err(&spi->dev, "Unable to setup SPI\n");
+ return ret;
+ }
+
+ /* Start the oscillator */
+ mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT);
+ /* Clear the 12 hour mode flag*/
+ 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);
+ if (IS_ERR(rtc))
+ return PTR_ERR(rtc);
+
+ spi_set_drvdata(spi, rtc);
+
+ return 0;
+}
+
+static struct spi_driver mcp795_driver = {
+ .driver = {
+ .name = "rtc-mcp795",
+ .owner = THIS_MODULE,
+ },
+ .probe = mcp795_probe,
+};
+
+module_spi_driver(mcp795_driver);
+
+MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
+MODULE_AUTHOR("Josef Gajdusek <atx@....name>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:mcp795");
--
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