[igt-dev] [PATCH i-g-t v3 2/4] lib/igt_pm: Find HDA device when attempting to enable runtime PM

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

HDA audio device can be present at various PCI paths on different systems
which the existing code did not account for.

Furthermore the failure to enable runtime PM was silent leaving callers
in the dark.

Improve it by auto-locating the PCI path and logging a warning when
something is not as expected.

v2:
 * If there is no audio hw/driver there is no failure.

v3
 * Comment.
 * Skip non-symlinks.
 * Free path on failure and restore.
 * Simplify with asprintf. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 lib/igt_pm.c | 76 ++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 59 insertions(+), 17 deletions(-)

diff --git a/lib/igt_pm.c b/lib/igt_pm.c
index 6f3b0a2d897d..fd2880c9df11 100644
--- a/lib/igt_pm.c
+++ b/lib/igt_pm.c
@@ -33,6 +33,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <dirent.h>
 
 #include "drmtest.h"
 #include "igt_pm.h"
@@ -64,6 +65,7 @@ enum {
 #define MAX_POLICY_STRLEN	strlen(MAX_PERFORMANCE_STR)
 
 static char __igt_pm_audio_runtime_power_save[64];
+static char * __igt_pm_audio_runtime_control_path;
 static char __igt_pm_audio_runtime_control[64];
 
 static int __igt_pm_audio_restore_runtime_pm(void)
@@ -86,7 +88,7 @@ static int __igt_pm_audio_restore_runtime_pm(void)
 
 	close(fd);
 
-	fd = open("/sys/bus/pci/devices/0000:00:03.0/power/control", O_WRONLY);
+	fd = open(__igt_pm_audio_runtime_control_path, O_WRONLY);
 	if (fd < 0)
 		return errno;
 
@@ -100,6 +102,8 @@ static int __igt_pm_audio_restore_runtime_pm(void)
 	close(fd);
 
 	__igt_pm_audio_runtime_power_save[0] = 0;
+	free(__igt_pm_audio_runtime_control_path);
+	__igt_pm_audio_runtime_control_path = NULL;
 
 	return 0;
 }
@@ -130,36 +134,74 @@ static void strchomp(char *str)
  */
 void igt_pm_enable_audio_runtime_pm(void)
 {
+	char *path = NULL;
+	struct dirent *de;
+	DIR *dir;
 	int fd;
 
 	/* Check if already enabled. */
 	if (__igt_pm_audio_runtime_power_save[0])
 		return;
 
-	fd = open("/sys/module/snd_hda_intel/parameters/power_save", O_RDWR);
-	if (fd >= 0) {
-		igt_assert(read(fd, __igt_pm_audio_runtime_power_save,
-				sizeof(__igt_pm_audio_runtime_power_save)) > 0);
-		strchomp(__igt_pm_audio_runtime_power_save);
-		igt_install_exit_handler(__igt_pm_audio_runtime_exit_handler);
-		igt_assert_eq(write(fd, "1\n", 2), 2);
-		close(fd);
-	}
-	fd = open("/sys/bus/pci/devices/0000:00:03.0/power/control", O_RDWR);
-	if (fd >= 0) {
-		igt_assert(read(fd, __igt_pm_audio_runtime_control,
-				sizeof(__igt_pm_audio_runtime_control)) > 0);
-		strchomp(__igt_pm_audio_runtime_control);
-		igt_assert_eq(write(fd, "auto\n", 5), 5);
-		close(fd);
+	dir = opendir("/sys/bus/pci/drivers/snd_hda_intel");
+	if (!dir)
+		return;
+
+	/* Find PCI device claimed by snd_hda_intel. */
+	while ((de = readdir(dir))) {
+		const char *match = "0000:00:";
+
+		if (de->d_type != DT_LNK ||
+		    strncmp(de->d_name, match, strlen(match)))
+			continue;
+
+		igt_assert(asprintf(&path,
+				    "/sys/bus/pci/devices/%s/power/control",
+				    de->d_name));
+
+		igt_debug("Audio device PCI path is %s\n", path);
+
+		break;
 	}
 
+	if (!path)
+		goto err;
+
+	fd = open("/sys/module/snd_hda_intel/parameters/power_save", O_RDWR);
+	if (fd < 0)
+		goto err;
+
+	igt_assert(read(fd, __igt_pm_audio_runtime_power_save,
+			sizeof(__igt_pm_audio_runtime_power_save)) > 0);
+	strchomp(__igt_pm_audio_runtime_power_save);
+	igt_install_exit_handler(__igt_pm_audio_runtime_exit_handler);
+	igt_assert_eq(write(fd, "1\n", 2), 2);
+	close(fd);
+
+	fd = open(path, O_RDWR);
+	if (fd < 0)
+		goto err;
+
+	igt_assert(read(fd, __igt_pm_audio_runtime_control,
+			sizeof(__igt_pm_audio_runtime_control)) > 0);
+	strchomp(__igt_pm_audio_runtime_control);
+	igt_assert_eq(write(fd, "auto\n", 5), 5);
+	close(fd);
+
+	__igt_pm_audio_runtime_control_path = path;
+
 	igt_debug("Saved audio power management as '%s' and '%s'\n",
 		  __igt_pm_audio_runtime_power_save,
 		  __igt_pm_audio_runtime_control);
 
 	/* Give some time for it to react. */
 	sleep(1);
+
+	return;
+
+err:
+	igt_warn("Failed to enable audio runtime PM! (%d)", errno);
+	free(path);
 }
 
 /**
-- 
2.17.1