[S390] ETR support.

This patch adds support for clock synchronization to an external time
reference (ETR). The external time reference sends an oscillator
signal and a synchronization signal every 2^20 microseconds to keep
the TOD clocks of all connected servers in sync. For availability
two ETR units can be connected to a machine. If the clock deviates
for more than the sync-check tolerance all cpus get a machine check
that indicates that the clock is out of sync. For the lovely details
how to get the clock back in sync see the code below.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

5 files changed, 72 insertions, 22 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index f208940c463..555e18a6b78 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -1232,6 +1232,19 @@ __dasd_process_blk_queue(struct dasd_device * device)
 		if (IS_ERR(cqr)) {
 			if (PTR_ERR(cqr) == -ENOMEM)
 				break;	/* terminate request queue loop */
+			if (PTR_ERR(cqr) == -EAGAIN) {
+				/*
+				 * The current request cannot be build right
+				 * now, we have to try later. If this request
+				 * is the head-of-queue we stop the device
+				 * for 1/2 second.
+				 */
+				if (!list_empty(&device->ccw_queue))
+					break;
+				device->stopped |= DASD_STOPPED_PENDING;
+				dasd_set_timer(device, HZ/2);
+				break;
+			}
 			DBF_DEV_EVENT(DBF_ERR, device,
 				      "CCW creation failed (rc=%ld) "
 				      "on request %p",
diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index d59115cce6d..a17d73193aa 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -204,37 +204,39 @@ recs_per_track(struct dasd_eckd_characteristics * rdc,
 	return 0;
 }
 
-static inline void
+static inline int
 check_XRC (struct ccw1         *de_ccw,
            struct DE_eckd_data *data,
            struct dasd_device  *device)
 {
         struct dasd_eckd_private *private;
+	int rc;
 
         private = (struct dasd_eckd_private *) device->private;
+	if (!private->rdc_data.facilities.XRC_supported)
+		return 0;
 
         /* switch on System Time Stamp - needed for XRC Support */
-        if (private->rdc_data.facilities.XRC_supported) {
-
-                data->ga_extended |= 0x08; /* switch on 'Time Stamp Valid'   */
-                data->ga_extended |= 0x02; /* switch on 'Extended Parameter' */
-
-                data->ep_sys_time = get_clock ();
-
-                de_ccw->count = sizeof (struct DE_eckd_data);
-		de_ccw->flags |= CCW_FLAG_SLI;
-        }
+	data->ga_extended |= 0x08; /* switch on 'Time Stamp Valid'   */
+	data->ga_extended |= 0x02; /* switch on 'Extended Parameter' */
 
-        return;
+	rc = get_sync_clock(&data->ep_sys_time);
+	/* Ignore return code if sync clock is switched off. */
+	if (rc == -ENOSYS || rc == -EACCES)
+		rc = 0;
 
-} /* end check_XRC */
+	de_ccw->count = sizeof (struct DE_eckd_data);
+	de_ccw->flags |= CCW_FLAG_SLI;
+	return rc;
+}
 
-static inline void
+static inline int
 define_extent(struct ccw1 * ccw, struct DE_eckd_data * data, int trk,
 	      int totrk, int cmd, struct dasd_device * device)
 {
 	struct dasd_eckd_private *private;
 	struct ch_t geo, beg, end;
+	int rc = 0;
 
 	private = (struct dasd_eckd_private *) device->private;
 
@@ -263,12 +265,12 @@ define_extent(struct ccw1 * ccw, struct DE_eckd_data * data, int trk,
 	case DASD_ECKD_CCW_WRITE_KD_MT:
 		data->mask.perm = 0x02;
 		data->attributes.operation = private->attrib.operation;
-                check_XRC (ccw, data, device);
+		rc = check_XRC (ccw, data, device);
 		break;
 	case DASD_ECKD_CCW_WRITE_CKD:
 	case DASD_ECKD_CCW_WRITE_CKD_MT:
 		data->attributes.operation = DASD_BYPASS_CACHE;
-                check_XRC (ccw, data, device);
+		rc = check_XRC (ccw, data, device);
 		break;
 	case DASD_ECKD_CCW_ERASE:
 	case DASD_ECKD_CCW_WRITE_HOME_ADDRESS:
@@ -276,7 +278,7 @@ define_extent(struct ccw1 * ccw, struct DE_eckd_data * data, int trk,
 		data->mask.perm = 0x3;
 		data->mask.auth = 0x1;
 		data->attributes.operation = DASD_BYPASS_CACHE;
-                check_XRC (ccw, data, device);
+		rc = check_XRC (ccw, data, device);
 		break;
 	default:
 		DEV_MESSAGE(KERN_ERR, device, "unknown opcode 0x%x", cmd);
@@ -312,6 +314,7 @@ define_extent(struct ccw1 * ccw, struct DE_eckd_data * data, int trk,
 	data->beg_ext.head = beg.head;
 	data->end_ext.cyl = end.cyl;
 	data->end_ext.head = end.head;
+	return rc;
 }
 
 static inline void
@@ -1200,7 +1203,12 @@ dasd_eckd_build_cp(struct dasd_device * device, struct request *req)
 		return cqr;
 	ccw = cqr->cpaddr;
 	/* First ccw is define extent. */
-	define_extent(ccw++, cqr->data, first_trk, last_trk, cmd, device);
+	if (define_extent(ccw++, cqr->data, first_trk,
+			  last_trk, cmd, device) == -EAGAIN) {
+		/* Clock not in sync and XRC is enabled. Try again later. */
+		dasd_sfree_request(cqr, device);
+		return ERR_PTR(-EAGAIN);
+	}
 	/* Build locate_record+read/write/ccws. */
 	idaws = (unsigned long *) (cqr->data + sizeof(struct DE_eckd_data));
 	LO_data = (struct LO_eckd_data *) (idaws + cidaw);
diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c
index 07a4cbfc243..ad2b3792984 100644
--- a/drivers/s390/cio/cio.c
+++ b/drivers/s390/cio/cio.c
@@ -646,7 +646,7 @@ do_IRQ (struct pt_regs *regs)
 		 * Make sure that the i/o interrupt did not "overtake"
 		 * the last HZ timer interrupt.
 		 */
-		account_ticks();
+		account_ticks(S390_lowcore.int_clock);
 	/*
 	 * Get interrupt information from lowcore
 	 */
@@ -850,6 +850,19 @@ __disable_subchannel_easy(struct subchannel_id schid, struct schib *schib)
 	return -EBUSY; /* uhm... */
 }
 
+/* we can't use the normal udelay here, since it enables external interrupts */
+
+static void udelay_reset(unsigned long usecs)
+{
+	uint64_t start_cc, end_cc;
+
+	asm volatile ("STCK %0" : "=m" (start_cc));
+	do {
+		cpu_relax();
+		asm volatile ("STCK %0" : "=m" (end_cc));
+	} while (((end_cc - start_cc)/4096) < usecs);
+}
+
 static inline int
 __clear_subchannel_easy(struct subchannel_id schid)
 {
@@ -865,7 +878,7 @@ __clear_subchannel_easy(struct subchannel_id schid)
 			if (schid_equal(&ti.schid, &schid))
 				return 0;
 		}
-		udelay(100);
+		udelay_reset(100);
 	}
 	return -EBUSY;
 }
diff --git a/drivers/s390/s390mach.c b/drivers/s390/s390mach.c
index 442d6347042..806bb1a921e 100644
--- a/drivers/s390/s390mach.c
+++ b/drivers/s390/s390mach.c
@@ -15,7 +15,7 @@
 #include <linux/time.h>
 #include <linux/device.h>
 #include <linux/kthread.h>
-
+#include <asm/etr.h>
 #include <asm/lowcore.h>
 #include <asm/cio.h>
 #include "cio/cio.h"
@@ -466,6 +466,19 @@ s390_do_machine_check(struct pt_regs *regs)
 			s390_handle_damage("unable to revalidate registers.");
 	}
 
+	if (mci->cd) {
+		/* Timing facility damage */
+		s390_handle_damage("TOD clock damaged");
+	}
+
+	if (mci->ed && mci->ec) {
+		/* External damage */
+		if (S390_lowcore.external_damage_code & (1U << ED_ETR_SYNC))
+			etr_sync_check();
+		if (S390_lowcore.external_damage_code & (1U << ED_ETR_SWITCH))
+			etr_switch_to_local();
+	}
+
 	if (mci->se)
 		/* Storage error uncorrected */
 		s390_handle_damage("received storage error uncorrected "
@@ -504,7 +517,7 @@ static int
 machine_check_init(void)
 {
 	init_MUTEX_LOCKED(&m_sem);
-	ctl_clear_bit(14, 25);	/* disable external damage MCH */
+	ctl_set_bit(14, 25);	/* enable external damage MCH */
 	ctl_set_bit(14, 27);    /* enable system recovery MCH */
 #ifdef CONFIG_MACHCHK_WARNING
 	ctl_set_bit(14, 24);	/* enable warning MCH */
diff --git a/drivers/s390/s390mach.h b/drivers/s390/s390mach.h
index 7abb42a09ae..d3ca4281a49 100644
--- a/drivers/s390/s390mach.h
+++ b/drivers/s390/s390mach.h
@@ -102,4 +102,7 @@ static inline int stcrw(struct crw *pcrw )
 	return ccode;
 }
 
+#define ED_ETR_SYNC	12	/* External damage ETR sync check */
+#define ED_ETR_SWITCH	13	/* External damage ETR switch to local */
+
 #endif /* __s390mach */