drm/i915/gt: Use the RPM config register to determine clk frequencies

For many configuration details within RC6 and RPS we are programming
intervals for the internal clocks. From gen11, these clocks are
configuration via the RPM_CONFIG and so for convenience, we would like
to convert to/from more natural units (ns).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200424162805.25920-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_gt_clock_utils.h

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2020 Intel Corporation
+ */
+
+#ifndef __INTEL_GT_CLOCK_UTILS_H__
+#define __INTEL_GT_CLOCK_UTILS_H__
+
+#include <linux/types.h>
+
+struct intel_gt;
+
+void intel_gt_init_clock_frequency(struct intel_gt *gt);
+
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
+void intel_gt_check_clock_frequency(const struct intel_gt *gt);
+#else
+static inline void intel_gt_check_clock_frequency(const struct intel_gt *gt) {}
+#endif
+
+u32 intel_gt_clock_interval_to_ns(const struct intel_gt *gt, u32 count);
+u32 intel_gt_pm_interval_to_ns(const struct intel_gt *gt, u32 count);
+
+u32 intel_gt_ns_to_clock_interval(const struct intel_gt *gt, u32 ns);
+u32 intel_gt_ns_to_pm_interval(const struct intel_gt *gt, u32 ns);
+
+#endif /* __INTEL_GT_CLOCK_UTILS_H__ */