s390/time: Add PtP driver

Add a small PtP driver which allows user space to get
the values of the physical and tod clock. This allows
programs like chrony to use STP as clock source and
steer the kernel clock. The physical clock can be used
as a debugging aid to get the clock without any additional
offsets like STP steering or LPAR offset.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Link: https://patch.msgid.link/20241023065601.449586-3-svens@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -20204,6 +20204,12 @@ F:	Documentation/arch/s390/pci.rst
 F:	arch/s390/pci/
 F:	drivers/pci/hotplug/s390_pci_hpc.c
 
+S390 PTP DRIVER
+M:	Sven Schnelle <svens@linux.ibm.com>
+L:	linux-s390@vger.kernel.org
+S:	Supported
+F:	drivers/ptp/ptp_s390.c
+
 S390 SCM DRIVER
 M:	Vineeth Vijayan <vneethv@linux.ibm.com>
 L:	linux-s390@vger.kernel.org

arch/s390/include/asm/stp.h

@@ -94,5 +94,6 @@ struct stp_stzi {
 int stp_sync_check(void);
 int stp_island_check(void);
 void stp_queue_work(void);
+bool stp_enabled(void);
 
 #endif /* __S390_STP_H */

arch/s390/include/asm/timex.h

@@ -93,6 +93,7 @@ extern unsigned char ptff_function_mask[16];
 #define PTFF_QAF	0x00	/* query available functions */
 #define PTFF_QTO	0x01	/* query tod offset */
 #define PTFF_QSI	0x02	/* query steering information */
+#define PTFF_QPT	0x03	/* query physical clock */
 #define PTFF_QUI	0x04	/* query UTC information */
 #define PTFF_ATO	0x40	/* adjust tod offset */
 #define PTFF_STO	0x41	/* set tod offset */
@@ -250,6 +251,11 @@ static __always_inline unsigned long tod_to_ns(unsigned long todval)
 	return ((todval >> 9) * 125) + (((todval & 0x1ff) * 125) >> 9);
 }
 
+static __always_inline u128 eitod_to_ns(u128 todval)
+{
+	return (todval * 125) >> 9;
+}
+
 /**
  * tod_after - compare two 64 bit TOD values
  * @a: first 64 bit TOD timestamp

arch/s390/kernel/time.c

@@ -469,6 +469,12 @@ static void __init stp_reset(void)
 	}
 }
 
+bool stp_enabled(void)
+{
+	return test_bit(CLOCK_SYNC_HAS_STP, &clock_sync_flags) && stp_online;
+}
+EXPORT_SYMBOL(stp_enabled);
+
 static void stp_timeout(struct timer_list *unused)
 {
 	queue_work(time_sync_wq, &stp_work);

drivers/ptp/Kconfig

@@ -237,4 +237,15 @@ config PTP_DFL_TOD
 	  To compile this driver as a module, choose M here: the module
 	  will be called ptp_dfl_tod.
 
+config PTP_S390
+	tristate "S390 PTP driver"
+	depends on PTP_1588_CLOCK
+	depends on S390
+	help
+	  This driver adds support for S390 time steering via the PtP
+	  interface. This works by adding a in-kernel clock delta value,
+	  which is always added to time values used in the kernel. The PtP
+	  driver provides the raw clock value without the delta to
+	  userspace. That way userspace programs like chrony could steer
+	  the kernel clock.
 endmenu

drivers/ptp/Makefile

@@ -22,3 +22,4 @@ obj-$(CONFIG_PTP_1588_CLOCK_MOCK)	+= ptp_mock.o
 obj-$(CONFIG_PTP_1588_CLOCK_VMW)	+= ptp_vmw.o
 obj-$(CONFIG_PTP_1588_CLOCK_OCP)	+= ptp_ocp.o
 obj-$(CONFIG_PTP_DFL_TOD)		+= ptp_dfl_tod.o
+obj-$(CONFIG_PTP_S390)			+= ptp_s390.o

drivers/ptp/ptp_s390.c

@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * s390 PTP clock driver
+ *
+ */
+
+#include "ptp_private.h"
+#include <linux/time.h>
+#include <asm/stp.h>
+
+static struct ptp_clock *ptp_stcke_clock, *ptp_qpt_clock;
+
+static int ptp_s390_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ptp_s390_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+	return -EOPNOTSUPP;
+}
+
+static struct timespec64 eitod_to_timespec64(union tod_clock *clk)
+{
+	return ns_to_timespec64(eitod_to_ns(clk->eitod - TOD_UNIX_EPOCH));
+}
+
+static struct timespec64 tod_to_timespec64(unsigned long tod)
+{
+	return ns_to_timespec64(tod_to_ns(tod - TOD_UNIX_EPOCH));
+}
+
+static int ptp_s390_stcke_gettime(struct ptp_clock_info *ptp,
+				  struct timespec64 *ts)
+{
+	union tod_clock tod;
+
+	if (!stp_enabled())
+		return -EOPNOTSUPP;
+
+	store_tod_clock_ext(&tod);
+	*ts = eitod_to_timespec64(&tod);
+	return 0;
+}
+
+static int ptp_s390_qpt_gettime(struct ptp_clock_info *ptp,
+				struct timespec64 *ts)
+{
+	unsigned long tod;
+
+	ptff(&tod, sizeof(tod), PTFF_QPT);
+	*ts = tod_to_timespec64(tod);
+	return 0;
+}
+
+static int ptp_s390_settime(struct ptp_clock_info *ptp,
+			    const struct timespec64 *ts)
+{
+	return -EOPNOTSUPP;
+}
+
+static int s390_arch_ptp_get_crosststamp(ktime_t *device_time,
+					 struct system_counterval_t *system_counter,
+					 void *ctx)
+{
+	union tod_clock clk;
+
+	store_tod_clock_ext(&clk);
+	*device_time = ns_to_ktime(tod_to_ns(clk.tod - TOD_UNIX_EPOCH));
+	system_counter->cycles = clk.tod;
+	system_counter->cs_id = CSID_S390_TOD;
+	return 0;
+}
+
+static int ptp_s390_getcrosststamp(struct ptp_clock_info *ptp,
+				   struct system_device_crosststamp *xtstamp)
+{
+	if (!stp_enabled())
+		return -EOPNOTSUPP;
+	return get_device_system_crosststamp(s390_arch_ptp_get_crosststamp, NULL, NULL, xtstamp);
+}
+
+static struct ptp_clock_info ptp_s390_stcke_info = {
+	.owner		= THIS_MODULE,
+	.name		= "s390 STCKE Clock",
+	.max_adj	= 0,
+	.adjfine	= ptp_s390_adjfine,
+	.adjtime	= ptp_s390_adjtime,
+	.gettime64	= ptp_s390_stcke_gettime,
+	.settime64	= ptp_s390_settime,
+	.getcrosststamp = ptp_s390_getcrosststamp,
+};
+
+static struct ptp_clock_info ptp_s390_qpt_info = {
+	.owner		= THIS_MODULE,
+	.name		= "s390 Physical Clock",
+	.max_adj	= 0,
+	.adjfine	= ptp_s390_adjfine,
+	.adjtime	= ptp_s390_adjtime,
+	.gettime64	= ptp_s390_qpt_gettime,
+	.settime64	= ptp_s390_settime,
+};
+
+static __init int ptp_s390_init(void)
+{
+	ptp_stcke_clock = ptp_clock_register(&ptp_s390_stcke_info, NULL);
+	if (IS_ERR(ptp_stcke_clock))
+		return PTR_ERR(ptp_stcke_clock);
+
+	ptp_qpt_clock = ptp_clock_register(&ptp_s390_qpt_info, NULL);
+	if (IS_ERR(ptp_qpt_clock)) {
+		ptp_clock_unregister(ptp_stcke_clock);
+		return PTR_ERR(ptp_qpt_clock);
+	}
+	return 0;
+}
+
+static __exit void ptp_s390_exit(void)
+{
+	ptp_clock_unregister(ptp_qpt_clock);
+	ptp_clock_unregister(ptp_stcke_clock);
+}
+
+module_init(ptp_s390_init);
+module_exit(ptp_s390_exit);
+
+MODULE_AUTHOR("Sven Schnelle <svens@linux.ibm.com>");
+MODULE_DESCRIPTION("s390 Physical/STCKE Clock PtP Driver");
+MODULE_LICENSE("GPL");