[kvm-unit-tests PATCH v8 11/12] 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
- 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.
- If the command succeeds but subchannel is not enabled 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 succesfuly.
This some 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>
---
 lib/s390x/css_lib.c | 60 +++++++++++++++++++++++++++++++++++++++++++++
 s390x/css.c         | 18 ++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/lib/s390x/css_lib.c b/lib/s390x/css_lib.c
index dc5a512..831a116 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 +69,62 @@ out:
 		    scn, scn_found, dev_found);
 	return schid;
 }
+
+int css_enable(int schid)
+{
+	struct pmcw *pmcw = &schib.pmcw;
+	int retry_count = 0;
+	int cc;
+
+	/* Read the SCHIB for this subchannel */
+	cc = stsch(schid, &schib);
+	if (cc) {
+		report_info("stsch failed with cc=%d", cc);
+		return cc;
+	}
+
+	if (pmcw->flags & PMCW_ENABLE) {
+		report_info("stsch: sch %08x already enabled", schid);
+		return 0;
+	}
+
+retry:
+	/* Update the SCHIB to enable the channel */
+	pmcw->flags |= PMCW_ENABLE;
+
+	/* 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 failed with cc=%d", cc);
+		return cc;
+	}
+
+	/*
+	 * Read the SCHIB again to verify the enablement
+	 */
+	cc = stsch(schid, &schib);
+	if (cc) {
+		report_info("stsch failed with cc=%d", cc);
+		return cc;
+	}
+
+	if (pmcw->flags & PMCW_ENABLE) {
+		report_info("Subchannel %08x enabled 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: enabling sch %08x failed after %d retries. pmcw flags: %x",
+		    schid, retry_count, pmcw->flags);
+	return -1;
+}
diff --git a/s390x/css.c b/s390x/css.c
index f0e8f47..6f58d4a 100644
--- a/s390x/css.c
+++ b/s390x/css.c
@@ -40,11 +40,29 @@ static void test_enumerate(void)
 	}
 }
 
+static void test_enable(void)
+{
+	int cc;
+
+	if (!test_device_sid) {
+		report_skip("No device");
+		return;
+	}
+
+	cc = css_enable(test_device_sid);
+
+	if (cc)
+		report(0, "Failed to enable subchannel %08x", test_device_sid);
+	else
+		report(1, "Subchannel %08x enabled", 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