From f4b18892dca8e629e0ce192b233579505f8ed343 Mon Sep 17 00:00:00 2001
From: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Date: Tue, 31 Dec 2019 16:00:07 +0200
Subject: [PATCH] drm/i915: Limit audio CDCLK>=2*BCLK constraint back to GLK only
Git-commit: f4b18892dca8e629e0ce192b233579505f8ed343
Patch-mainline: v5.5-rc6
No-fix: 1ee48a61aa57dbdbc3cd2808d8b28df40d938e44
References: git-fixes

Revert changes done in commit f6ec9483091f ("drm/i915: extend audio
CDCLK>=2*BCLK constraint to more platforms"). Audio drivers
communicate with i915 over HDA bus multiple times during system
boot-up and each of these transactions result in matching
get_power/put_power calls to i915, and depending on the platform,
a modeset change causing visible flicker.

GLK is the only platform with minimum CDCLK significantly lower
than BCLK, and thus for GLK setting a higher CDCLK is mandatory.

For other platforms, minimum CDCLK is close but below 2*BCLK
(e.g. on ICL, CDCLK=176.4kHz with BCLK=96kHz). Spec-wise the constraint
should be set, but in practise no communication errors have been
reported and the downside if set is the flicker observed at boot-time.

Revert to old behaviour until better mechanism to manage
probe-time clocks is available.

The full CDCLK>=2*BCLK constraint is still enforced at pipe
enable time in intel_crtc_compute_min_cdclk().

Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/913
Fixes: f6ec9483091f ("drm/i915: extend audio CDCLK>=2*BCLK constraint to more platforms")
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191231140007.31728-1-kai.vehmanen@linux.intel.com
(cherry picked from commit 1ee48a61aa57dbdbc3cd2808d8b28df40d938e44)

Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/display/intel_audio.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/i915/display/intel_audio.c
+++ b/drivers/gpu/drm/i915/display/intel_audio.c
@@ -853,7 +853,7 @@ static unsigned long i915_audio_componen
 	/* Force CDCLK to 2*BCLK as long as we need audio to be powered. */
 	if (dev_priv->audio_power_refcount++ == 0)
 		/* Force CDCLK to 2*BCLK as long as we need audio powered. */
-		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
+		if (IS_GEMINILAKE(dev_priv))
 			glk_force_audio_cdclk(dev_priv, true);
 
 	return ret;
@@ -866,7 +866,7 @@ static void i915_audio_component_put_pow
 
 	/* Stop forcing CDCLK to 2*BCLK if no need for audio to be powered. */
 	if (--dev_priv->audio_power_refcount == 0)
-		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
+		if (IS_GEMINILAKE(dev_priv))
 			glk_force_audio_cdclk(dev_priv, false);
 
 	intel_display_power_put(dev_priv, POWER_DOMAIN_AUDIO, cookie);