[PATCH i-g-t 4/5] lib/igt_kms: Add igt_get_max_cdclk()

[Swati Sharma <swati2.sharma@intel.com>]

Add igt_get_max_cdclk() to return max cdclk frequency.

Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
---
 lib/igt_kms.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 50 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 8220cc0eb..aa5dfa8ce 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -6390,6 +6390,55 @@ int igt_get_max_dotclock(int fd)
 	return max_dotclock;
 }
 
+/**
+ * igt_get_max_cdclk:
+ * @fd: A drm file descriptor
+ *
+ * Get the Max CD clock frequency from intel specific debugfs
+ * "i915_frequency_info" (or) "i915_cdclk_info".
+ *
+ * Returns: Max supported CD clock frequency.
+ */
+int igt_get_max_cdclk(int fd)
+{
+	char buf[4096];
+	char *s;
+	int dir, res, max_cdclk = 0;
+	drmModeRes *resources;
+
+	if (!is_intel_device(fd))
+		return max_cdclk;
+
+	/* If there is no display, then no point to check for cdclk. */
+	resources = drmModeGetResources(fd);
+	if (!resources)
+		return max_cdclk;
+
+	drmModeFreeResources(resources);
+
+	dir = igt_debugfs_dir(fd);
+	igt_require(dir != -1);
+
+	/*
+	 * Display specific clock frequency info is moved to i915_cdclk_info,
+	 * On older kernels if this debugfs is not found, fallback to read from
+	 * i915_frequency_info.
+	 */
+	res = igt_debugfs_simple_read(dir, "i915_cdclk_info",
+				      buf, sizeof(buf));
+	if (res <= 0)
+		res = igt_debugfs_simple_read(dir, "i915_frequency_info",
+					      buf, sizeof(buf));
+	close(dir);
+
+	igt_require(res > 0);
+
+	igt_assert(s = strstr(buf, "Max CD clock frequency:"));
+	igt_assert_eq(sscanf(s, "Max CD clock frequency: %d kHz", &max_cdclk), 1);
+
+	return max_cdclk;
+}
+
 /**
  * igt_bigjoiner_possible:
  * @drm_fd: drm file descriptor
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 5cf0b89d3..e6665abdd 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1244,6 +1244,7 @@ void igt_sort_connector_modes(drmModeConnector *connector,
 bool igt_max_bpc_constraint(igt_display_t *display, enum pipe pipe,
 		igt_output_t *output, int bpc);
 int igt_get_max_dotclock(int fd);
+int igt_get_max_cdclk(int fd);
 bool igt_bigjoiner_possible(int drm_fd, drmModeModeInfo *mode, int max_dotclock);
 bool bigjoiner_mode_found(int drm_fd, drmModeConnector *connector,
 			  int max_dotclock, drmModeModeInfo *mode);
-- 
2.25.1