[PATCH i-g-t] tests/i915_suspend: Refresh device list after *-without-i915 subtests

[Janusz Krzysztofik]

If any of *-without-i915 subtests fails or skips for any reason, it may
leave the i915 module unloaded while keeping our device list populated
with initially collected data.  In a follow up igt_fixture section we then
try to reopen the device.  If the test has been executed with a device
filter specified, an attempt to open the device finds a matching entry
that belongs to the no longer existing device in that initially collected
device list, fails to stat() it, concludes that's because of the device
having been already open, and returns an error.

Fix this potentially confusing test result by refreshing the potentially
outdated device list before continuing with drm_open_driver() if we've
been called with a device filter specified.

While being at it, add a comment that explains why we call
igt_devices_scan() from __igt_device_card_match() but don't force device
rescan, and emit a debug message if we fail in _is_already_opened() on
unsuccessful device stat().

v2: don't free the device list -- we can't tell if it has been populated,
    and igt_devices_free() fails if it hasn't.

Subtest basic-s3-without-i915: FAIL (9.572s)
(i915_suspend:9050) drmtest-WARNING: card maching filter 0 is already opened
(i915_suspend:9050) drmtest-CRITICAL: Test abort in function drm_open_driver, file ../lib/drmtest.c:639:
(i915_suspend:9050) drmtest-CRITICAL: abort condition: fd < 0
(i915_suspend:9050) drmtest-CRITICAL: Last errno: 2, No such file or directory
(i915_suspend:9050) drmtest-CRITICAL: No known gpu found for chipset flags 0x1 (intel)
Test i915_suspend failed.
**** DEBUG ****
(i915_suspend:9050) drmtest-DEBUG: Looking for devices to open using filter 0: pci:vendor=intel,device=dg2
(i915_suspend:9050) drmtest-DEBUG: Filter matched /dev/dri/card0 | /dev/dri/renderD128
(i915_suspend:9050) drmtest-WARNING: card maching filter 0 is already opened
(i915_suspend:9050) drmtest-CRITICAL: Test abort in function drm_open_driver, file ../lib/drmtest.c:639:
(i915_suspend:9050) drmtest-CRITICAL: abort condition: fd < 0
(i915_suspend:9050) drmtest-CRITICAL: Last errno: 2, No such file or directory
(i915_suspend:9050) drmtest-CRITICAL: No known gpu found for chipset flags 0x1 (intel)
(i915_suspend:9050) igt_core-INFO: Stack trace:
(i915_suspend:9050) igt_core-INFO:   #0 ../lib/igt_core.c:2066 __igt_abort()
(i915_suspend:9050) igt_core-INFO:   #1 ../lib/drmtest.c:573 drm_open_driver()
(i915_suspend:9050) igt_core-INFO:   #2 ../tests/i915/i915_suspend.c:258 __igt_unique____real_main245()
(i915_suspend:9050) igt_core-INFO:   #3 ../tests/i915/i915_suspend.c:245 main()
(i915_suspend:9050) igt_core-INFO:   #4 ../sysdeps/nptl/libc_start_call_main.h:58 __libc_start_call_main()
(i915_suspend:9050) igt_core-INFO:   #5 ../csu/libc-start.c:128 __libc_start_main@@GLIBC_2.34()
(i915_suspend:9050) igt_core-INFO:   #6 [_start+0x2a]
****  END  ****

Fixes: f7aff600ab16 ("tests/i915/i915_suspend: Disable d3cold_allowed for basic-s2idle-without-i915")
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Cc: Riana Tauro <riana.tauro at intel.com>
---
 lib/drmtest.c             |  2 +-
 lib/igt_device_scan.c     |  4 ++++
 tests/i915/i915_suspend.c | 12 +++++++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/drmtest.c b/lib/drmtest.c
index 16e80bdfcf..8e2d1ac50b 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -260,7 +260,7 @@ static bool _is_already_opened(const char *path, int as_idx)
 	 * we cannot even stat the device, so it's of no use - let's claim it's
 	 * already opened
 	 */
-	if (stat(path, &new) != 0)
+	if (igt_debug_on(stat(path, &new) != 0))
 		return true;
 
 	for (int i = 0; i < as_idx; ++i) {
diff --git a/lib/igt_device_scan.c b/lib/igt_device_scan.c
index 8b767eed20..ae69ed09f1 100644
--- a/lib/igt_device_scan.c
+++ b/lib/igt_device_scan.c
@@ -1918,6 +1918,10 @@ static bool __igt_device_card_match(const char *filter,
 		return false;
 	memset(card, 0, sizeof(*card));
 
+	/*
+	 * Scan devices in case the user hasn't yet,
+	 * but leave a decision on forced rescan on the user side.
+	 */
 	igt_devices_scan(false);
 
 	if (igt_device_filter_apply(filter) == false)
diff --git a/tests/i915/i915_suspend.c b/tests/i915/i915_suspend.c
index 815f1c8a2c..1d304a9317 100644
--- a/tests/i915/i915_suspend.c
+++ b/tests/i915/i915_suspend.c
@@ -253,8 +253,18 @@ igt_main
 	igt_subtest("basic-s3-without-i915")
 		test_suspend_without_i915(SUSPEND_STATE_S3);
 
-	igt_fixture
+	igt_fixture {
+		/*
+		 * Since above subtests may fail, leaving i915 module unloaded
+		 * but device list populated, refresh the device list before
+		 * reopening the i915 device if we've been called with a device
+		 * filter specified, otherwise drm_open_driver() will fail
+		 * instead of reloading the i915 module.
+		 */
+		if (igt_device_filter_count())
+			igt_devices_scan(true);
 		fd = drm_open_driver(DRIVER_INTEL);
+	}
 
 	igt_subtest("fence-restore-tiled2untiled") {
 		gem_require_mappable_ggtt(fd);
-- 
2.25.1