[kvm-unit-tests PATCH v13 8/9] s390x: css: msch, enable test

[Pierre Morel <pmorel@linux.ibm.com>]

A second step when testing the channel subsystem is to prepare a channel
for use.
This includes:
- Get the current subchannel Information Block (SCHIB) using STSCH
- Update it in memory to set the ENABLE bit and the specified ISC
- Tell the CSS that the SCHIB has been modified using MSCH
- Get the SCHIB from the CSS again to verify that the subchannel is
  enabled and uses the specified ISC.
- If the command succeeds but subchannel is not enabled or the ISC
  field is not as expected, retry a predefined retries count.
- If the command fails, report the failure and do not retry, even
  if cc indicates a busy/status pending as we do not expect this.

This tests the MSCH instruction to enable a channel successfully.
Retries are done and in case of error, and if the retries count
is exceeded, a report is made.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 lib/s390x/css.h     |  9 ++++--
 lib/s390x/css_lib.c | 73 +++++++++++++++++++++++++++++++++++++++++++++
 s390x/css.c         | 15 ++++++++++
 3 files changed, 94 insertions(+), 3 deletions(-)

diff --git a/lib/s390x/css.h b/lib/s390x/css.h
index 0ddceb1..63a70f1 100644
--- a/lib/s390x/css.h
+++ b/lib/s390x/css.h
@@ -71,8 +71,10 @@ struct scsw {
 
 struct pmcw {
 	uint32_t intparm;
-#define PMCW_DNV        0x0001
-#define PMCW_ENABLE     0x0080
+#define PMCW_DNV	0x0001
+#define PMCW_ENABLE	0x0080
+#define PMCW_ISC_MASK	0x3800
+#define PMCW_ISC_SHIFT	11
 	uint16_t flags;
 	uint16_t devnum;
 	uint8_t  lpm;
@@ -251,6 +253,7 @@ void dump_orb(struct orb *op);
 
 int css_enumerate(void);
 #define MAX_ENABLE_RETRIES      5
-int css_enable(int schid);
 
+#define IO_SCH_ISC      3
+int css_enable(int schid, int isc);
 #endif
diff --git a/lib/s390x/css_lib.c b/lib/s390x/css_lib.c
index fd087ce..e47a945 100644
--- a/lib/s390x/css_lib.c
+++ b/lib/s390x/css_lib.c
@@ -15,6 +15,7 @@
 #include <string.h>
 #include <interrupt.h>
 #include <asm/arch_def.h>
+#include <asm/time.h>
 
 #include <css.h>
 
@@ -68,3 +69,75 @@ out:
 		    scn, scn_found, dev_found);
 	return schid;
 }
+
+/*
+ * css_enable: enable the subchannel with the specified ISC
+ * @schid: Subchannel Identifier
+ * @isc  : number of the interruption subclass to use
+ * Return value:
+ *   On success: 0
+ *   On error the CC of the faulty instruction
+ *      or -1 if the retry count is exceeded.
+ */
+int css_enable(int schid, int isc)
+{
+	struct pmcw *pmcw = &schib.pmcw;
+	int retry_count = 0;
+	uint16_t flags;
+	int cc;
+
+	/* Read the SCHIB for this subchannel */
+	cc = stsch(schid, &schib);
+	if (cc) {
+		report_info("stsch: sch %08x failed with cc=%d", schid, cc);
+		return cc;
+	}
+
+	flags = PMCW_ENABLE | (isc << PMCW_ISC_SHIFT);
+	if ((pmcw->flags & (PMCW_ISC_MASK | PMCW_ENABLE)) == flags) {
+		report_info("stsch: sch %08x already enabled", schid);
+		return 0;
+	}
+
+retry:
+	/* Update the SCHIB to enable the channel and set the ISC */
+	pmcw->flags &= ~PMCW_ISC_MASK;
+	pmcw->flags |= flags;
+
+	/* Tell the CSS we want to modify the subchannel */
+	cc = msch(schid, &schib);
+	if (cc) {
+		/*
+		 * If the subchannel is status pending or
+		 * if a function is in progress,
+		 * we consider both cases as errors.
+		 */
+		report_info("msch: sch %08x failed with cc=%d", schid, cc);
+		return cc;
+	}
+
+	/*
+	 * Read the SCHIB again to verify the enablement
+	 */
+	cc = stsch(schid, &schib);
+	if (cc) {
+		report_info("stsch: updating sch %08x failed with cc=%d",
+			    schid, cc);
+		return cc;
+	}
+
+	if ((pmcw->flags & flags) == flags) {
+		report_info("stsch: sch %08x successfully modified after %d retries",
+			    schid, retry_count);
+		return 0;
+	}
+
+	if (retry_count++ < MAX_ENABLE_RETRIES) {
+		mdelay(10); /* the hardware was not ready, give it some time */
+		goto retry;
+	}
+
+	report_info("msch: modifying sch %08x failed after %d retries. pmcw flags: %04x",
+		    schid, retry_count, pmcw->flags);
+	return -1;
+}
diff --git a/s390x/css.c b/s390x/css.c
index e19ffc8..f314a0c 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -31,11 +31,26 @@ static void test_enumerate(void)
 	report(0, "No I/O device found");
 }
 
+static void test_enable(void)
+{
+	int cc;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+
+	cc = css_enable(test_device_sid, IO_SCH_ISC);
+
+	report(cc == 0, "Enable subchannel %08x", test_device_sid);
+}
+
 static struct {
 	const char *name;
 	void (*func)(void);
 } tests[] = {
 	{ "enumerate (stsch)", test_enumerate },
+	{ "enable (msch)", test_enable },
 	{ NULL, NULL }
 };
 
-- 
2.25.1