Add the Intel Series PCH built-in read-only RTC. This driver is not for
in-system use on x86 but rather is for external access over I2C from a BMC.
Signed-off-by: Ivan Mikhaylov <[email protected]>
---
drivers/rtc/Kconfig | 10 +++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-pch.c | 148 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 159 insertions(+)
create mode 100644 drivers/rtc/rtc-pch.c
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 12153d5801ce..4f31bcbf0736 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -555,6 +555,16 @@ config RTC_DRV_PALMAS
This driver can also be built as a module. If so, the module
will be called rtc-palma.
+config RTC_DRV_PCH
+ tristate "PCH RTC driver"
+ help
+ If you say yes here you get support for the Intel Series PCH
+ built-in read-only RTC. This driver is not for in-system use on x86,
+ but rather is for external access over I2C from a BMC.
+
+ This driver can also be built as a module. If so, the module
+ will be called rtc-pch.
+
config RTC_DRV_TPS6586X
tristate "TI TPS6586X RTC driver"
depends on MFD_TPS6586X
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 2dd0dd956b0e..cb2804433d87 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -121,6 +121,7 @@ obj-$(CONFIG_RTC_DRV_PCF8523) += rtc-pcf8523.o
obj-$(CONFIG_RTC_DRV_PCF85363) += rtc-pcf85363.o
obj-$(CONFIG_RTC_DRV_PCF8563) += rtc-pcf8563.o
obj-$(CONFIG_RTC_DRV_PCF8583) += rtc-pcf8583.o
+obj-$(CONFIG_RTC_DRV_PCH) += rtc-pch.o
obj-$(CONFIG_RTC_DRV_PIC32) += rtc-pic32.o
obj-$(CONFIG_RTC_DRV_PL030) += rtc-pl030.o
obj-$(CONFIG_RTC_DRV_PL031) += rtc-pl031.o
diff --git a/drivers/rtc/rtc-pch.c b/drivers/rtc/rtc-pch.c
new file mode 100644
index 000000000000..a2918257bf39
--- /dev/null
+++ b/drivers/rtc/rtc-pch.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * I2C read-only RTC driver for PCH with additional sysfs attribute for host
+ * power control.
+ *
+ * Copyright (C) 2021 YADRO
+ */
+
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define PCH_REG_FORCE_OFF 0x00
+#define PCH_REG_SC 0x09
+#define PCH_REG_MN 0x0a
+#define PCH_REG_HR 0x0b
+#define PCH_REG_DW 0x0c
+#define PCH_REG_DM 0x0d
+#define PCH_REG_MO 0x0e
+#define PCH_REG_YR 0x0f
+
+#define NUM_TIME_REGS (PCH_REG_YR - PCH_REG_SC + 1)
+
+struct pch {
+ struct rtc_device *rtc;
+ struct regmap *regmap;
+};
+
+static int pch_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct pch *pch = i2c_get_clientdata(client);
+ unsigned char rtc_data[NUM_TIME_REGS] = {0};
+ int rc;
+
+ rc = regmap_bulk_read(pch->regmap, PCH_REG_SC, rtc_data, NUM_TIME_REGS);
+ if (rc < 0) {
+ dev_err(dev, "fail to read time reg(%d)\n", rc);
+ return rc;
+ }
+
+ tm->tm_sec = bcd2bin(rtc_data[0]);
+ tm->tm_min = bcd2bin(rtc_data[1]);
+ tm->tm_hour = bcd2bin(rtc_data[2]);
+ tm->tm_wday = rtc_data[3];
+ tm->tm_mday = bcd2bin(rtc_data[4]);
+ tm->tm_mon = bcd2bin(rtc_data[5]) - 1;
+ tm->tm_year = bcd2bin(rtc_data[6]) + 100;
+
+ return 0;
+}
+
+static ssize_t force_off_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct pch *pch = i2c_get_clientdata(client);
+ unsigned long val;
+ int rc;
+
+ if (kstrtoul(buf, 10, &val))
+ return -EINVAL;
+
+ if (val) {
+ /* 0x02 host force off */
+ rc = regmap_write(pch->regmap, PCH_REG_FORCE_OFF, 0x2);
+ if (rc < 0) {
+ dev_err(dev, "Fail to read time reg(%d)\n", rc);
+ return rc;
+ }
+ }
+
+ return 0;
+}
+static DEVICE_ATTR_WO(force_off);
+
+static const struct rtc_class_ops pch_rtc_ops = {
+ .read_time = pch_rtc_read_time,
+};
+
+static const struct regmap_config pch_rtc_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .use_single_read = true,
+};
+
+static int pch_rtc_probe(struct i2c_client *client)
+{
+ struct pch *pch;
+ int rc;
+
+ pch = devm_kzalloc(&client->dev, sizeof(*pch), GFP_KERNEL);
+ if (!pch)
+ return -ENOMEM;
+
+ pch->regmap = devm_regmap_init_i2c(client, &pch_rtc_regmap_config);
+ if (IS_ERR(pch->regmap)) {
+ dev_err(&client->dev, "regmap_init failed\n");
+ return PTR_ERR(pch->regmap);
+ }
+
+ i2c_set_clientdata(client, pch);
+
+ pch->rtc = devm_rtc_device_register(&client->dev, "pch-rtc",
+ &pch_rtc_ops, THIS_MODULE);
+ if (IS_ERR(pch->rtc)) {
+ dev_err(&client->dev, "rtc device register failed\n");
+ return PTR_ERR(pch->rtc);
+ }
+
+ rc = sysfs_create_file(&client->dev.kobj, &dev_attr_force_off.attr);
+ if (rc) {
+ dev_err(&client->dev, "couldn't create sysfs attr : %i\n", rc);
+ return rc;
+ }
+
+ return 0;
+}
+
+static int pch_rtc_remove(struct i2c_client *client)
+{
+ sysfs_remove_file(&client->dev.kobj, &dev_attr_force_off.attr);
+ return 0;
+}
+
+static const struct of_device_id pch_rtc_of_match[] = {
+ { .compatible = "intel,pch-rtc", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, pch_rtc_of_match);
+
+static struct i2c_driver pch_rtc_driver = {
+ .driver = {
+ .name = "pch-rtc",
+ .of_match_table = pch_rtc_of_match,
+ },
+ .probe_new = pch_rtc_probe,
+ .remove = pch_rtc_remove,
+};
+module_i2c_driver(pch_rtc_driver);
+
+MODULE_DESCRIPTION("RTC PCH driver");
+MODULE_AUTHOR("Ivan Mikhaylov <[email protected]>");
+MODULE_LICENSE("GPL");
--
2.31.1
On Tue, Aug 10, 2021 at 06:44:35PM +0300, Ivan Mikhaylov wrote:
> +config RTC_DRV_PCH
> + tristate "PCH RTC driver"
> + help
> + If you say yes here you get support for the Intel Series PCH
I'm afraid this is really lacking some specification of devices that
are supported. Is it really everything that Intel currently calls PCH?
> +static int pch_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct pch *pch = i2c_get_clientdata(client);
> + unsigned char rtc_data[NUM_TIME_REGS] = {0};
> + int rc;
> +
> + rc = regmap_bulk_read(pch->regmap, PCH_REG_SC, rtc_data, NUM_TIME_REGS);
> + if (rc < 0) {
> + dev_err(dev, "fail to read time reg(%d)\n", rc);
> + return rc;
> + }
Citing 26.7.2.3 from C620 (Lewisburg/Purley) datasheet:
"The PCH SMBus slave interface only supports Byte Read operation. The
external SMBus master will read the RTC time bytes one after
another. It is software’s responsibility to check and manage the
possible time rollover when subsequent time bytes are read.
For example, assuming the RTC time is 11 hours: 59 minutes: 59
seconds. When the external SMBus master reads the hour as 11, then
proceeds to read the minute, it is possible that the rollover happens
between the reads and the minute is read as 0. This results in 11
hours: 0 minutes instead of the correct time of 12 hours: 0 minutes.
Unless it is certain that rollover will not occur, software is
required to detect the possible time rollover by reading multiple
times such that the read time bytes can be adjusted accordingly if
needed."
Should this be taken additional care of somehow?
> +static ssize_t force_off_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct pch *pch = i2c_get_clientdata(client);
> + unsigned long val;
> + int rc;
> +
> + if (kstrtoul(buf, 10, &val))
> + return -EINVAL;
> +
> + if (val) {
> + /* 0x02 host force off */
I wonder why you write "host force off" while the C620 datasheet calls
it "Unconditional Power Down", does your PCH manual use different
naming?
In any case this doesn't belong to an RTC driver, as previously noted.
--
Be free, use free (http://www.gnu.org/philosophy/free-sw.html) software!
mailto:[email protected]
On Tue, Aug 15, 2021 at 01:52:42PM +0300, Paul Fertser wrote:
> On Tue, Aug 10, 2021 at 06:44:35PM +0300, Ivan Mikhaylov wrote:
> > +config RTC_DRV_PCH
> > + tristate "PCH RTC driver"
> > + help
> > + If you say yes here you get support for the Intel Series PCH
>
> I'm afraid this is really lacking some specification of devices that
> are supported. Is it really everything that Intel currently calls PCH?
Yes, from infromation that I know.
> > +static int pch_rtc_read_time(struct device *dev, struct rtc_time *tm)
> > +{
> > + struct i2c_client *client = to_i2c_client(dev);
> > + struct pch *pch = i2c_get_clientdata(client);
> > + unsigned char rtc_data[NUM_TIME_REGS] = {0};
> > + int rc;
> > +
> > + rc = regmap_bulk_read(pch->regmap, PCH_REG_SC, rtc_data, NUM_TIME_REGS);
> > + if (rc < 0) {
> > + dev_err(dev, "fail to read time reg(%d)\n", rc);
> > + return rc;
> > + }
>
> Citing 26.7.2.3 from C620 (Lewisburg/Purley) datasheet:
>
> "The PCH SMBus slave interface only supports Byte Read operation. The
> external SMBus master will read the RTC time bytes one after
> another. It is software’s responsibility to check and manage the
> possible time rollover when subsequent time bytes are read.
>
> For example, assuming the RTC time is 11 hours: 59 minutes: 59
> seconds. When the external SMBus master reads the hour as 11, then
> proceeds to read the minute, it is possible that the rollover happens
> between the reads and the minute is read as 0. This results in 11
> hours: 0 minutes instead of the correct time of 12 hours: 0 minutes.
> Unless it is certain that rollover will not occur, software is
> required to detect the possible time rollover by reading multiple
> times such that the read time bytes can be adjusted accordingly if
> needed."
>
> Should this be taken additional care of somehow?
1. .use_single_read in regmap_config.
2. Maybe that is the right place for rollover check.
> > +static ssize_t force_off_store(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct i2c_client *client = to_i2c_client(dev);
> > + struct pch *pch = i2c_get_clientdata(client);
> > + unsigned long val;
> > + int rc;
> > +
> > + if (kstrtoul(buf, 10, &val))
> > + return -EINVAL;
> > +
> > + if (val) {
> > + /* 0x02 host force off */
>
> I wonder why you write "host force off" while the C620 datasheet calls
> it "Unconditional Power Down", does your PCH manual use different
> naming?
It just a synonym, does the same. I can change it but first it's need to
be decided if attribute would go or not.
Thanks.
On 20/08/2021 15:34:10+0300, Ivan Mikhaylov wrote:
> On Tue, Aug 15, 2021 at 01:52:42PM +0300, Paul Fertser wrote:
> > On Tue, Aug 10, 2021 at 06:44:35PM +0300, Ivan Mikhaylov wrote:
> > > +config RTC_DRV_PCH
> > > + tristate "PCH RTC driver"
> > > + help
> > > + If you say yes here you get support for the Intel Series PCH
> >
> > I'm afraid this is really lacking some specification of devices that
> > are supported. Is it really everything that Intel currently calls PCH?
>
> Yes, from infromation that I know.
>
> > > +static int pch_rtc_read_time(struct device *dev, struct rtc_time *tm)
> > > +{
> > > + struct i2c_client *client = to_i2c_client(dev);
> > > + struct pch *pch = i2c_get_clientdata(client);
> > > + unsigned char rtc_data[NUM_TIME_REGS] = {0};
> > > + int rc;
> > > +
> > > + rc = regmap_bulk_read(pch->regmap, PCH_REG_SC, rtc_data, NUM_TIME_REGS);
> > > + if (rc < 0) {
> > > + dev_err(dev, "fail to read time reg(%d)\n", rc);
> > > + return rc;
> > > + }
> >
> > Citing 26.7.2.3 from C620 (Lewisburg/Purley) datasheet:
> >
> > "The PCH SMBus slave interface only supports Byte Read operation. The
> > external SMBus master will read the RTC time bytes one after
> > another. It is software’s responsibility to check and manage the
> > possible time rollover when subsequent time bytes are read.
> >
> > For example, assuming the RTC time is 11 hours: 59 minutes: 59
> > seconds. When the external SMBus master reads the hour as 11, then
> > proceeds to read the minute, it is possible that the rollover happens
> > between the reads and the minute is read as 0. This results in 11
> > hours: 0 minutes instead of the correct time of 12 hours: 0 minutes.
> > Unless it is certain that rollover will not occur, software is
> > required to detect the possible time rollover by reading multiple
> > times such that the read time bytes can be adjusted accordingly if
> > needed."
> >
> > Should this be taken additional care of somehow?
>
> 1. .use_single_read in regmap_config.
> 2. Maybe that is the right place for rollover check.
>
> > > +static ssize_t force_off_store(struct device *dev,
> > > + struct device_attribute *attr,
> > > + const char *buf, size_t count)
> > > +{
> > > + struct i2c_client *client = to_i2c_client(dev);
> > > + struct pch *pch = i2c_get_clientdata(client);
> > > + unsigned long val;
> > > + int rc;
> > > +
> > > + if (kstrtoul(buf, 10, &val))
> > > + return -EINVAL;
> > > +
> > > + if (val) {
> > > + /* 0x02 host force off */
> >
> > I wonder why you write "host force off" while the C620 datasheet calls
> > it "Unconditional Power Down", does your PCH manual use different
> > naming?
>
> It just a synonym, does the same. I can change it but first it's need to
> be decided if attribute would go or not.
>
I would prefer if this was added later on in a later patch, with the
proper ABI documentation so that the ABI can be discussed.
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com