[kvm-unit-tests PATCH v2 1/8] s390x: lib: css: disabling a subchannel

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

Some tests require to disable a subchannel.
Let's implement the css_disable() function.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 lib/s390x/css.h     |  1 +
 lib/s390x/css_lib.c | 67 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/lib/s390x/css.h b/lib/s390x/css.h
index 7e3d261..b0de3a3 100644
--- a/lib/s390x/css.h
+++ b/lib/s390x/css.h
@@ -284,6 +284,7 @@ int css_enumerate(void);
 #define IO_SCH_ISC      3
 int css_enable(int schid, int isc);
 bool css_enabled(int schid);
+int css_disable(int schid);
 
 /* Library functions */
 int start_ccw1_chain(unsigned int sid, struct ccw1 *ccw);
diff --git a/lib/s390x/css_lib.c b/lib/s390x/css_lib.c
index efc7057..f5c4f37 100644
--- a/lib/s390x/css_lib.c
+++ b/lib/s390x/css_lib.c
@@ -186,6 +186,73 @@ bool css_enabled(int schid)
 	}
 	return true;
 }
+
+/*
+ * css_disable: disable the subchannel
+ * @schid: Subchannel Identifier
+ * Return value:
+ *   On success: 0
+ *   On error the CC of the faulty instruction
+ *      or -1 if the retry count is exceeded.
+ */
+int css_disable(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: sch %08x failed with cc=%d", schid, cc);
+		return cc;
+	}
+
+	if (!(pmcw->flags & PMCW_ENABLE)) {
+		report_info("stsch: sch %08x already disabled", schid);
+		return 0;
+	}
+
+retry:
+	/* Update the SCHIB to disable the subchannel */
+	pmcw->flags &= ~PMCW_ENABLE;
+
+	/* Tell the CSS we want to modify the subchannel */
+	cc = msch(schid, &schib);
+	/*
+	 * If the subchannel is status pending or if a function is in progress,
+	 * we consider both cases as errors.
+	 */
+	if (cc) {
+		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 & PMCW_ENABLE)) {
+		if (retry_count)
+			report_info("stsch: sch %08x successfully disabled after %d retries",
+				    schid, retry_count);
+		return 0;
+	}
+
+	if (retry_count++ < MAX_ENABLE_RETRIES) {
+		/* the hardware was not ready, give it some time */
+		mdelay(10);
+		goto retry;
+	}
+
+	report_info("msch: modifying sch %08x failed after %d retries. pmcw flags: %04x",
+		    schid, retry_count, pmcw->flags);
+	return -1;
+}
 /*
  * css_enable: enable the subchannel with the specified ISC
  * @schid: Subchannel Identifier
-- 
2.17.1