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From: Lyude Paul <lyude@redhat.com>
To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
	intel-gfx@lists.freedesktop.org
Cc: "Jani Nikula" <jani.nikula@intel.com>,
	"Anshuman Gupta" <anshuman.gupta@intel.com>,
	"David Airlie" <airlied@linux.ie>,
	"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
	"Lucas De Marchi" <lucas.demarchi@intel.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Gwan-gyeong Mun" <gwan-gyeong.mun@intel.com>,
	"Manasi Navare" <manasi.d.navare@intel.com>,
	greg.depoire@gmail.com, "Uma Shankar" <uma.shankar@intel.com>,
	"Sean Paul" <seanpaul@chromium.org>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Dave Airlie" <airlied@redhat.com>,
	"Imre Deak" <imre.deak@intel.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>
Subject: [Nouveau] [RFC v3 03/10] drm/i915/dpcd_bl: Remove redundant AUX backlight frequency calculations
Date: Fri,  5 Feb 2021 18:45:07 -0500
Message-ID: <20210205234515.1216538-4-lyude@redhat.com> (raw)
In-Reply-To: <20210205234515.1216538-1-lyude@redhat.com>

Noticed this while moving all of the VESA backlight code in i915 over to
DRM helpers: it would appear that we calculate the frequency value we want
to write to DP_EDP_BACKLIGHT_FREQ_SET twice even though this value never
actually changes during runtime. So, let's simplify things by just caching
this value in intel_panel.backlight, and re-writing it as-needed.

Changes since v1:
* Wrap panel->backlight.edp.vesa.pwm_freq_pre_divider in
  DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP check - Jani

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Dave Airlie <airlied@gmail.com>
Cc: greg.depoire@gmail.com
---
 .../drm/i915/display/intel_display_types.h    |  1 +
 .../drm/i915/display/intel_dp_aux_backlight.c | 65 ++++++-------------
 2 files changed, 20 insertions(+), 46 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 307ff4b771f4..f4b26e1dbaaf 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -264,6 +264,7 @@ struct intel_panel {
 		union {
 			struct {
 				u8 pwmgen_bit_count;
+				u8 pwm_freq_pre_divider;
 			} vesa;
 			struct {
 				bool sdr_uses_aux;
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index 651884390137..62294967f430 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -373,50 +373,6 @@ intel_dp_aux_vesa_set_backlight(const struct drm_connector_state *conn_state,
 	}
 }
 
-/*
- * Set PWM Frequency divider to match desired frequency in vbt.
- * The PWM Frequency is calculated as 27Mhz / (F x P).
- * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 of the
- *             EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
- * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of the
- *             EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
- */
-static bool intel_dp_aux_vesa_set_pwm_freq(struct intel_connector *connector)
-{
-	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
-	struct intel_dp *intel_dp = intel_attached_dp(connector);
-	const u8 pn = connector->panel.backlight.edp.vesa.pwmgen_bit_count;
-	int freq, fxp, f, fxp_actual, fxp_min, fxp_max;
-
-	freq = dev_priv->vbt.backlight.pwm_freq_hz;
-	if (!freq) {
-		drm_dbg_kms(&dev_priv->drm,
-			    "Use panel default backlight frequency\n");
-		return false;
-	}
-
-	fxp = DIV_ROUND_CLOSEST(KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ), freq);
-	f = clamp(DIV_ROUND_CLOSEST(fxp, 1 << pn), 1, 255);
-	fxp_actual = f << pn;
-
-	/* Ensure frequency is within 25% of desired value */
-	fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
-	fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
-
-	if (fxp_min > fxp_actual || fxp_actual > fxp_max) {
-		drm_dbg_kms(&dev_priv->drm, "Actual frequency out of range\n");
-		return false;
-	}
-
-	if (drm_dp_dpcd_writeb(&intel_dp->aux,
-			       DP_EDP_BACKLIGHT_FREQ_SET, (u8) f) < 0) {
-		drm_dbg_kms(&dev_priv->drm,
-			    "Failed to write aux backlight freq\n");
-		return false;
-	}
-	return true;
-}
-
 static void
 intel_dp_aux_vesa_enable_backlight(const struct intel_crtc_state *crtc_state,
 				   const struct drm_connector_state *conn_state, u32 level)
@@ -459,9 +415,13 @@ intel_dp_aux_vesa_enable_backlight(const struct intel_crtc_state *crtc_state,
 		break;
 	}
 
-	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP)
-		if (intel_dp_aux_vesa_set_pwm_freq(connector))
+	if (panel->backlight.edp.vesa.pwm_freq_pre_divider) {
+		if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_FREQ_SET,
+				       panel->backlight.edp.vesa.pwm_freq_pre_divider) == 1)
 			new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
+		else
+			drm_dbg_kms(&i915->drm, "Failed to write aux backlight frequency\n");
+	}
 
 	if (new_dpcd_buf != dpcd_buf) {
 		if (drm_dp_dpcd_writeb(&intel_dp->aux,
@@ -482,6 +442,14 @@ static void intel_dp_aux_vesa_disable_backlight(const struct drm_connector_state
 				  false);
 }
 
+/*
+ * Compute PWM frequency divider value based off the frequency provided to us by the vbt.
+ * The PWM Frequency is calculated as 27Mhz / (F x P).
+ * - Where F = PWM Frequency Pre-Divider value programmed by field 7:0 of the
+ *             EDP_BACKLIGHT_FREQ_SET register (DPCD Address 00728h)
+ * - Where P = 2^Pn, where Pn is the value programmed by field 4:0 of the
+ *             EDP_PWMGEN_BIT_COUNT register (DPCD Address 00724h)
+ */
 static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connector)
 {
 	struct drm_i915_private *i915 = to_i915(connector->base.dev);
@@ -533,8 +501,10 @@ static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connecto
 	pn_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
 	pn_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
 
+	/* Ensure frequency is within 25% of desired value */
 	fxp_min = DIV_ROUND_CLOSEST(fxp * 3, 4);
 	fxp_max = DIV_ROUND_CLOSEST(fxp * 5, 4);
+
 	if (fxp_min < (1 << pn_min) || (255 << pn_max) < fxp_max) {
 		drm_dbg_kms(&i915->drm,
 			    "VBT defined backlight frequency out of range\n");
@@ -555,7 +525,10 @@ static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connecto
 			    "Failed to write aux pwmgen bit count\n");
 		return max_backlight;
 	}
+
 	panel->backlight.edp.vesa.pwmgen_bit_count = pn;
+	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP)
+		panel->backlight.edp.vesa.pwm_freq_pre_divider = f;
 
 	max_backlight = (1 << pn) - 1;
 
-- 
2.29.2

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  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05 23:45 [Nouveau] [RFC v3 00/10] drm: Extract DPCD backlight helpers from i915, add support in nouveau Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 01/10] drm/nouveau/kms/nv40-/backlight: Assign prop type once Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 02/10] drm/nouveau/kms: Don't probe eDP connectors more then once Lyude Paul
2021-02-05 23:45 ` Lyude Paul [this message]
2021-02-05 23:45 ` [Nouveau] [RFC v3 04/10] drm/i915/dpcd_bl: Handle drm_dpcd_read/write() return values correctly Lyude Paul
2021-02-08 11:11   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 05/10] drm/i915/dpcd_bl: Cleanup intel_dp_aux_vesa_enable_backlight() a bit Lyude Paul
2021-02-06  0:07   ` Ilia Mirkin
2021-02-05 23:45 ` [Nouveau] [RFC v3 06/10] drm/i915/dpcd_bl: Cache some backlight capabilities in intel_panel.backlight Lyude Paul
2021-02-08 11:13   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 07/10] drm/i915/dpcd_bl: Move VESA backlight enabling code closer together Lyude Paul
2021-02-08 11:14   ` Rodrigo Vivi
2021-02-05 23:45 ` [Nouveau] [RFC v3 08/10] drm/i915/dpcd_bl: Return early in vesa_calc_max_backlight if we can't read PWMGEN_BIT_COUNT Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 09/10] drm/i915/dpcd_bl: Print return codes for VESA backlight failures Lyude Paul
2021-02-05 23:45 ` [Nouveau] [RFC v3 10/10] drm/dp: Extract i915's eDP backlight code into DRM helpers Lyude Paul
2021-02-08  8:46   ` Thomas Zimmermann
2021-02-08 23:03     ` Lyude Paul
2021-02-15 18:34       ` Thomas Zimmermann
2021-02-15 20:26         ` Lyude Paul
2021-02-08 22:52 ` [Nouveau] [RFC v3 00/10] drm: Extract DPCD backlight helpers from i915, add support in nouveau Lyude Paul

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