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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: David Airlie <airlied@linux.ie>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	open list <linux-kernel@vger.kernel.org>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Sean Paul <seanpaul@chromium.org>,
	Daniel Vetter <daniel@ffwll.ch>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: [Nouveau] [RFC v3 08/10] drm/i915/dpcd_bl: Return early in vesa_calc_max_backlight if we can't read PWMGEN_BIT_COUNT
Date: Fri,  5 Feb 2021 18:45:12 -0500
Message-ID: <20210205234515.1216538-9-lyude@redhat.com> (raw)
In-Reply-To: <20210205234515.1216538-1-lyude@redhat.com>

If we can't read DP_EDP_PWMGEN_BIT_COUNT in
intel_dp_aux_vesa_calc_max_backlight() but do have a valid PWM frequency
defined in the VBT, we'll keep going in the function until we inevitably
fail on reading DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN. There's not much point in
doing this, so just return early.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

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 431758058aa0..c66350cdf7e9 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -449,11 +449,14 @@ static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connecto
 	int freq, fxp, fxp_min, fxp_max, fxp_actual, f = 1;
 	u8 pn, pn_min, pn_max;
 
-	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) == 1) {
-		pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
-		max_backlight = (1 << pn) - 1;
+	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT, &pn) != 1) {
+		drm_dbg_kms(&i915->drm, "Failed to read pwmgen bit count cap\n");
+		return 0;
 	}
 
+	pn &= DP_EDP_PWMGEN_BIT_COUNT_MASK;
+	max_backlight = (1 << pn) - 1;
+
 	/* Find desired value of (F x P)
 	 * Note that, if F x P is out of supported range, the maximum value or
 	 * minimum value will applied automatically. So no need to check that.
-- 
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 ` [Nouveau] [RFC v3 03/10] drm/i915/dpcd_bl: Remove redundant AUX backlight frequency calculations Lyude Paul
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 ` Lyude Paul [this message]
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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