[gentoo-commits] proj/linux-patches:5.15 commit in: /

["Mike Pagano" <mpagano@gentoo.org>]

commit:     b75b7e6a336c28fa493be98a01eef5ce375e020b
Author:     Mike Pagano <mpagano <AT> gentoo <DOT> org>
AuthorDate: Mon Nov 29 23:34:54 2021 +0000
Commit:     Mike Pagano <mpagano <AT> gentoo <DOT> org>
CommitDate: Mon Nov 29 23:34:54 2021 +0000
URL:        https://gitweb.gentoo.org/proj/linux-patches.git/commit/?id=b75b7e6a

Add suprt for panels w. VESA backlights with PWM enable/disable

Signed-off-by: Mike Pagano <mpagano <AT> gentoo.org>

 0000_README                                        |   4 +
 ...15-PWM-support-for-VESA-backlight-helpers.patch | 618 +++++++++++++++++++++
 2 files changed, 622 insertions(+)

diff --git a/0000_README b/0000_README
index 68d0c0db..0923a646 100644
--- a/0000_README
+++ b/0000_README
@@ -75,6 +75,10 @@ Patch:  2000_BT-Check-key-sizes-only-if-Secure-Simple-Pairing-enabled.patch
 From:   https://lore.kernel.org/linux-bluetooth/20190522070540.48895-1-marcel@holtmann.org/raw
 Desc:   Bluetooth: Check key sizes only when Secure Simple Pairing is enabled. See bug #686758
 
+Patch:  2800_drm-i915-PWM-support-for-VESA-backlight-helpers.patch 
+From:   https://patchwork.freedesktop.org/series/95127/
+Desc:   drm/i915: Add support for panels with VESA backlights with PWM enable/disable
+
 Patch:  2900_tmp513-Fix-build-issue-by-selecting-CONFIG_REG.patch
 From:   https://bugs.gentoo.org/710790
 Desc:   tmp513 requies REGMAP_I2C to build.  Select it by default in Kconfig. See bug #710790. Thanks to Phil Stracchino

diff --git a/2800_drm-i915-PWM-support-for-VESA-backlight-helpers.patch b/2800_drm-i915-PWM-support-for-VESA-backlight-helpers.patch
new file mode 100644
index 00000000..45969bce
--- /dev/null
+++ b/2800_drm-i915-PWM-support-for-VESA-backlight-helpers.patch
@@ -0,0 +1,618 @@
+From patchwork Fri Nov  5 18:33:38 2021
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
+Subject: [v5,1/5] drm/i915: Add support for panels with VESA backlights with
+ PWM enable/disable
+From: Lyude Paul <lyude@redhat.com>
+X-Patchwork-Id: 462369
+Message-Id: <20211105183342.130810-2-lyude@redhat.com>
+To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
+ intel-gfx@lists.freedesktop.org
+Cc: David Airlie <airlied@linux.ie>, open list <linux-kernel@vger.kernel.org>,
+ stable@vger.kernel.org
+Date: Fri,  5 Nov 2021 14:33:38 -0400
+
+This simply adds proper support for panel backlights that can be controlled
+via VESA's backlight control protocol, but which also require that we
+enable and disable the backlight via PWM instead of via the DPCD interface.
+We also enable this by default, in order to fix some people's backlights
+that were broken by not having this enabled.
+
+For reference, backlights that require this and use VESA's backlight
+interface tend to be laptops with hybrid GPUs, but this very well may
+change in the future.
+
+v4:
+* Make sure that we call intel_backlight_level_to_pwm() in
+  intel_dp_aux_vesa_enable_backlight() - vsyrjala
+
+Signed-off-by: Lyude Paul <lyude@redhat.com>
+Link: https://gitlab.freedesktop.org/drm/intel/-/issues/3680
+Fixes: fe7d52bccab6 ("drm/i915/dp: Don't use DPCD backlights that need PWM enable/disable")
+Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
+Cc: <stable@vger.kernel.org> # v5.12+
+---
+ .../drm/i915/display/intel_dp_aux_backlight.c | 27 ++++++++++++++-----
+ 1 file changed, 21 insertions(+), 6 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 569d17b4d00f..f05b71c01b8e 100644
+--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
++++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+@@ -293,6 +293,13 @@ intel_dp_aux_vesa_enable_backlight(const struct intel_crtc_state *crtc_state,
+ 	struct intel_panel *panel = &connector->panel;
+ 	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ 
++	if (!panel->backlight.edp.vesa.info.aux_enable) {
++		u32 pwm_level = intel_backlight_invert_pwm_level(connector,
++								 panel->backlight.pwm_level_max);
++
++		panel->backlight.pwm_funcs->enable(crtc_state, conn_state, pwm_level);
++	}
++
+ 	drm_edp_backlight_enable(&intel_dp->aux, &panel->backlight.edp.vesa.info, level);
+ }
+ 
+@@ -304,6 +311,10 @@ static void intel_dp_aux_vesa_disable_backlight(const struct drm_connector_state
+ 	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ 
+ 	drm_edp_backlight_disable(&intel_dp->aux, &panel->backlight.edp.vesa.info);
++
++	if (!panel->backlight.edp.vesa.info.aux_enable)
++		panel->backlight.pwm_funcs->disable(old_conn_state,
++						    intel_backlight_invert_pwm_level(connector, 0));
+ }
+ 
+ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector, enum pipe pipe)
+@@ -321,6 +332,15 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
+ 	if (ret < 0)
+ 		return ret;
+ 
++	if (!panel->backlight.edp.vesa.info.aux_enable) {
++		ret = panel->backlight.pwm_funcs->setup(connector, pipe);
++		if (ret < 0) {
++			drm_err(&i915->drm,
++				"Failed to setup PWM backlight controls for eDP backlight: %d\n",
++				ret);
++			return ret;
++		}
++	}
+ 	panel->backlight.max = panel->backlight.edp.vesa.info.max;
+ 	panel->backlight.min = 0;
+ 	if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
+@@ -340,12 +360,7 @@ intel_dp_aux_supports_vesa_backlight(struct intel_connector *connector)
+ 	struct intel_dp *intel_dp = intel_attached_dp(connector);
+ 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+ 
+-	/* TODO: We currently only support AUX only backlight configurations, not backlights which
+-	 * require a mix of PWM and AUX controls to work. In the mean time, these machines typically
+-	 * work just fine using normal PWM controls anyway.
+-	 */
+-	if ((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
+-	    drm_edp_backlight_supported(intel_dp->edp_dpcd)) {
++	if (drm_edp_backlight_supported(intel_dp->edp_dpcd)) {
+ 		drm_dbg_kms(&i915->drm, "AUX Backlight Control Supported!\n");
+ 		return true;
+ 	}
+
+From patchwork Fri Nov  5 18:33:39 2021
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: [v5,2/5] drm/nouveau/kms/nv50-: Explicitly check DPCD backlights for
+ aux enable/brightness
+From: Lyude Paul <lyude@redhat.com>
+X-Patchwork-Id: 462371
+Message-Id: <20211105183342.130810-3-lyude@redhat.com>
+To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
+ intel-gfx@lists.freedesktop.org
+Cc: David Airlie <airlied@linux.ie>, Ben Skeggs <bskeggs@redhat.com>,
+ Karol Herbst <kherbst@redhat.com>, open list <linux-kernel@vger.kernel.org>
+Date: Fri,  5 Nov 2021 14:33:39 -0400
+
+Since we don't support hybrid AUX/PWM backlights in nouveau right now,
+let's add some explicit checks so that we don't break nouveau once we
+enable support for these backlights in other drivers.
+
+Reviewed-by: Karol Herbst <kherbst@redhat.com>
+Signed-off-by: Lyude Paul <lyude@redhat.com>
+---
+ drivers/gpu/drm/nouveau/nouveau_backlight.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
+index 1cbd71abc80a..ae2f2abc8f5a 100644
+--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
++++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
+@@ -308,7 +308,10 @@ nv50_backlight_init(struct nouveau_backlight *bl,
+ 		if (ret < 0)
+ 			return ret;
+ 
+-		if (drm_edp_backlight_supported(edp_dpcd)) {
++		/* TODO: Add support for hybrid PWM/DPCD panels */
++		if (drm_edp_backlight_supported(edp_dpcd) &&
++		    (edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
++		    (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) {
+ 			NV_DEBUG(drm, "DPCD backlight controls supported on %s\n",
+ 				 nv_conn->base.name);
+ 
+
+From patchwork Fri Nov  5 18:33:40 2021
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: [v5,3/5] drm/dp: Don't read back backlight mode in
+ drm_edp_backlight_enable()
+From: Lyude Paul <lyude@redhat.com>
+X-Patchwork-Id: 462376
+Message-Id: <20211105183342.130810-4-lyude@redhat.com>
+To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
+ intel-gfx@lists.freedesktop.org
+Cc: Thomas Zimmermann <tzimmermann@suse.de>, David Airlie <airlied@linux.ie>,
+ open list <linux-kernel@vger.kernel.org>, Maxime Ripard <mripard@kernel.org>
+Date: Fri,  5 Nov 2021 14:33:40 -0400
+
+As it turns out, apparently some machines will actually leave additional
+backlight functionality like dynamic backlight control on before the OS
+loads. Currently we don't take care to disable unsupported features when
+writing back the backlight mode, which can lead to some rather strange
+looking behavior when adjusting the backlight.
+
+So, let's fix this by just not reading back the current backlight mode on
+initial enable. I don't think there should really be any downsides to this,
+and this will ensure we don't leave any unsupported functionality enabled.
+
+This should fix at least one (but not all) of the issues seen with DPCD
+backlight support on fi-bdw-samus
+
+v5:
+* Just avoid reading back DPCD register - Doug Anderson
+
+Signed-off-by: Lyude Paul <lyude@redhat.com>
+Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers")
+Reviewed-by: Douglas Anderson <dianders@chromium.org>
+---
+ drivers/gpu/drm/drm_dp_helper.c | 40 ++++++++++-----------------------
+ 1 file changed, 12 insertions(+), 28 deletions(-)
+
+diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
+index ada0a1ff262d..af2aad2f4725 100644
+--- a/drivers/gpu/drm/drm_dp_helper.c
++++ b/drivers/gpu/drm/drm_dp_helper.c
+@@ -3363,27 +3363,13 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli
+ 			     const u16 level)
+ {
+ 	int ret;
+-	u8 dpcd_buf, new_dpcd_buf;
++	u8 dpcd_buf = DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+ 
+-	ret = drm_dp_dpcd_readb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf);
+-	if (ret != 1) {
+-		drm_dbg_kms(aux->drm_dev,
+-			    "%s: Failed to read backlight mode: %d\n", aux->name, ret);
+-		return ret < 0 ? ret : -EIO;
+-	}
+-
+-	new_dpcd_buf = dpcd_buf;
+-
+-	if ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) != DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
+-		new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
+-		new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+-
+-		if (bl->pwmgen_bit_count) {
+-			ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count);
+-			if (ret != 1)
+-				drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n",
+-					    aux->name, ret);
+-		}
++	if (bl->pwmgen_bit_count) {
++		ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count);
++		if (ret != 1)
++			drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n",
++				    aux->name, ret);
+ 	}
+ 
+ 	if (bl->pwm_freq_pre_divider) {
+@@ -3393,16 +3379,14 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli
+ 				    "%s: Failed to write aux backlight frequency: %d\n",
+ 				    aux->name, ret);
+ 		else
+-			new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
++			dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
+ 	}
+ 
+-	if (new_dpcd_buf != dpcd_buf) {
+-		ret = drm_dp_dpcd_writeb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf);
+-		if (ret != 1) {
+-			drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux backlight mode: %d\n",
+-				    aux->name, ret);
+-			return ret < 0 ? ret : -EIO;
+-		}
++	ret = drm_dp_dpcd_writeb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf);
++	if (ret != 1) {
++		drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux backlight mode: %d\n",
++			    aux->name, ret);
++		return ret < 0 ? ret : -EIO;
+ 	}
+ 
+ 	ret = drm_edp_backlight_set_level(aux, bl, level);
+
+From patchwork Fri Nov  5 18:33:41 2021
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: [v5,4/5] drm/dp,
+ drm/i915: Add support for VESA backlights using PWM for brightness control
+From: Lyude Paul <lyude@redhat.com>
+X-Patchwork-Id: 462379
+Message-Id: <20211105183342.130810-5-lyude@redhat.com>
+To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
+ intel-gfx@lists.freedesktop.org
+Cc: Rajeev Nandan <rajeevny@codeaurora.org>, David Airlie <airlied@linux.ie>,
+ Doug Anderson <dianders@chromium.org>, Maxime Ripard <mripard@kernel.org>,
+ open list <linux-kernel@vger.kernel.org>,
+ Thomas Zimmermann <tzimmermann@suse.de>
+Date: Fri,  5 Nov 2021 14:33:41 -0400
+
+Now that we've added support to i915 for controlling panel backlights that
+need PWM to be enabled/disabled, let's finalize this and add support for
+controlling brightness levels via PWM as well. This should hopefully put us
+towards the path of supporting _ALL_ backlights via VESA's DPCD interface
+which would allow us to finally start trusting the DPCD again.
+
+Note however that we still don't enable using this by default on i915 when
+it's not needed, primarily because I haven't yet had a chance to confirm if
+it's safe to do this on the one machine in Intel's CI that had an issue
+with this: samus-fi-bdw. I have done basic testing of this on other
+machines though, by manually patching i915 to force it into PWM-only mode
+on some of my laptops.
+
+v2:
+* Correct documentation (thanks Doug!)
+* Get rid of backlight caps
+
+Signed-off-by: Lyude Paul <lyude@redhat.com>
+Reviewed-by: Doug Anderson <dianders@chromium.org>
+Cc: Rajeev Nandan <rajeevny@codeaurora.org>
+Cc: Satadru Pramanik <satadru@gmail.com>
+---
+ drivers/gpu/drm/drm_dp_helper.c               | 72 +++++++++++++------
+ .../drm/i915/display/intel_dp_aux_backlight.c | 44 +++++++++---
+ include/drm/drm_dp_helper.h                   |  7 +-
+ 3 files changed, 89 insertions(+), 34 deletions(-)
+
+diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
+index af2aad2f4725..23f9073bc473 100644
+--- a/drivers/gpu/drm/drm_dp_helper.c
++++ b/drivers/gpu/drm/drm_dp_helper.c
+@@ -3290,6 +3290,10 @@ int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct drm_edp_bac
+ 	int ret;
+ 	u8 buf[2] = { 0 };
+ 
++	/* The panel uses the PWM for controlling brightness levels */
++	if (!bl->aux_set)
++		return 0;
++
+ 	if (bl->lsb_reg_used) {
+ 		buf[0] = (level & 0xff00) >> 8;
+ 		buf[1] = (level & 0x00ff);
+@@ -3316,7 +3320,7 @@ drm_edp_backlight_set_enable(struct drm_dp_aux *aux, const struct drm_edp_backli
+ 	int ret;
+ 	u8 buf;
+ 
+-	/* The panel uses something other then DPCD for enabling its backlight */
++	/* This panel uses the EDP_BL_PWR GPIO for enablement */
+ 	if (!bl->aux_enable)
+ 		return 0;
+ 
+@@ -3351,11 +3355,11 @@ drm_edp_backlight_set_enable(struct drm_dp_aux *aux, const struct drm_edp_backli
+  * restoring any important backlight state such as the given backlight level, the brightness byte
+  * count, backlight frequency, etc.
+  *
+- * Note that certain panels, while supporting brightness level controls over DPCD, may not support
+- * having their backlights enabled via the standard %DP_EDP_DISPLAY_CONTROL_REGISTER. On such panels
+- * &drm_edp_backlight_info.aux_enable will be set to %false, this function will skip the step of
+- * programming the %DP_EDP_DISPLAY_CONTROL_REGISTER, and the driver must perform the required
+- * implementation specific step for enabling the backlight after calling this function.
++ * Note that certain panels do not support being enabled or disabled via DPCD, but instead require
++ * that the driver handle enabling/disabling the panel through implementation-specific means using
++ * the EDP_BL_PWR GPIO. For such panels, &drm_edp_backlight_info.aux_enable will be set to %false,
++ * this function becomes a no-op, and the driver is expected to handle powering the panel on using
++ * the EDP_BL_PWR GPIO.
+  *
+  * Returns: %0 on success, negative error code on failure.
+  */
+@@ -3363,7 +3367,12 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli
+ 			     const u16 level)
+ {
+ 	int ret;
+-	u8 dpcd_buf = DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
++	u8 dpcd_buf;
++
++	if (bl->aux_set)
++		dpcd_buf = DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
++	else
++		dpcd_buf = DP_EDP_BACKLIGHT_CONTROL_MODE_PWM;
+ 
+ 	if (bl->pwmgen_bit_count) {
+ 		ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count);
+@@ -3405,12 +3414,13 @@ EXPORT_SYMBOL(drm_edp_backlight_enable);
+  * @aux: The DP AUX channel to use
+  * @bl: Backlight capability info from drm_edp_backlight_init()
+  *
+- * This function handles disabling DPCD backlight controls on a panel over AUX. Note that some
+- * panels have backlights that are enabled/disabled by other means, despite having their brightness
+- * values controlled through DPCD. On such panels &drm_edp_backlight_info.aux_enable will be set to
+- * %false, this function will become a no-op (and we will skip updating
+- * %DP_EDP_DISPLAY_CONTROL_REGISTER), and the driver must take care to perform it's own
+- * implementation specific step for disabling the backlight.
++ * This function handles disabling DPCD backlight controls on a panel over AUX.
++ *
++ * Note that certain panels do not support being enabled or disabled via DPCD, but instead require
++ * that the driver handle enabling/disabling the panel through implementation-specific means using
++ * the EDP_BL_PWR GPIO. For such panels, &drm_edp_backlight_info.aux_enable will be set to %false,
++ * this function becomes a no-op, and the driver is expected to handle powering the panel off using
++ * the EDP_BL_PWR GPIO.
+  *
+  * Returns: %0 on success or no-op, negative error code on failure.
+  */
+@@ -3434,6 +3444,9 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
+ 	int ret;
+ 	u8 pn, pn_min, pn_max;
+ 
++	if (!bl->aux_set)
++		return 0;
++
+ 	ret = drm_dp_dpcd_readb(aux, DP_EDP_PWMGEN_BIT_COUNT, &pn);
+ 	if (ret != 1) {
+ 		drm_dbg_kms(aux->drm_dev, "%s: Failed to read pwmgen bit count cap: %d\n",
+@@ -3519,7 +3532,7 @@ drm_edp_backlight_probe_max(struct drm_dp_aux *aux, struct drm_edp_backlight_inf
+ }
+ 
+ static inline int
+-drm_edp_backlight_probe_level(struct drm_dp_aux *aux, struct drm_edp_backlight_info *bl,
++drm_edp_backlight_probe_state(struct drm_dp_aux *aux, struct drm_edp_backlight_info *bl,
+ 			      u8 *current_mode)
+ {
+ 	int ret;
+@@ -3534,6 +3547,9 @@ drm_edp_backlight_probe_level(struct drm_dp_aux *aux, struct drm_edp_backlight_i
+ 	}
+ 
+ 	*current_mode = (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK);
++	if (!bl->aux_set)
++		return 0;
++
+ 	if (*current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
+ 		int size = 1 + bl->lsb_reg_used;
+ 
+@@ -3564,7 +3580,7 @@ drm_edp_backlight_probe_level(struct drm_dp_aux *aux, struct drm_edp_backlight_i
+  * @bl: The &drm_edp_backlight_info struct to fill out with information on the backlight
+  * @driver_pwm_freq_hz: Optional PWM frequency from the driver in hz
+  * @edp_dpcd: A cached copy of the eDP DPCD
+- * @current_level: Where to store the probed brightness level
++ * @current_level: Where to store the probed brightness level, if any
+  * @current_mode: Where to store the currently set backlight control mode
+  *
+  * Initializes a &drm_edp_backlight_info struct by probing @aux for it's backlight capabilities,
+@@ -3584,24 +3600,38 @@ drm_edp_backlight_init(struct drm_dp_aux *aux, struct drm_edp_backlight_info *bl
+ 
+ 	if (edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP)
+ 		bl->aux_enable = true;
++	if (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)
++		bl->aux_set = true;
+ 	if (edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+ 		bl->lsb_reg_used = true;
+ 
++	/* Sanity check caps */
++	if (!bl->aux_set && !(edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) {
++		drm_dbg_kms(aux->drm_dev,
++			    "%s: Panel supports neither AUX or PWM brightness control? Aborting\n",
++			    aux->name);
++		return -EINVAL;
++	}
++
+ 	ret = drm_edp_backlight_probe_max(aux, bl, driver_pwm_freq_hz, edp_dpcd);
+ 	if (ret < 0)
+ 		return ret;
+ 
+-	ret = drm_edp_backlight_probe_level(aux, bl, current_mode);
++	ret = drm_edp_backlight_probe_state(aux, bl, current_mode);
+ 	if (ret < 0)
+ 		return ret;
+ 	*current_level = ret;
+ 
+ 	drm_dbg_kms(aux->drm_dev,
+-		    "%s: Found backlight level=%d/%d pwm_freq_pre_divider=%d mode=%x\n",
+-		    aux->name, *current_level, bl->max, bl->pwm_freq_pre_divider, *current_mode);
+-	drm_dbg_kms(aux->drm_dev,
+-		    "%s: Backlight caps: pwmgen_bit_count=%d lsb_reg_used=%d aux_enable=%d\n",
+-		    aux->name, bl->pwmgen_bit_count, bl->lsb_reg_used, bl->aux_enable);
++		    "%s: Found backlight: aux_set=%d aux_enable=%d mode=%d\n",
++		    aux->name, bl->aux_set, bl->aux_enable, *current_mode);
++	if (bl->aux_set) {
++		drm_dbg_kms(aux->drm_dev,
++			    "%s: Backlight caps: level=%d/%d pwm_freq_pre_divider=%d lsb_reg_used=%d\n",
++			    aux->name, *current_level, bl->max, bl->pwm_freq_pre_divider,
++			    bl->lsb_reg_used);
++	}
++
+ 	return 0;
+ }
+ EXPORT_SYMBOL(drm_edp_backlight_init);
+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 f05b71c01b8e..96fe3eaba44a 100644
+--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
++++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+@@ -282,6 +282,12 @@ intel_dp_aux_vesa_set_backlight(const struct drm_connector_state *conn_state, u3
+ 	struct intel_panel *panel = &connector->panel;
+ 	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ 
++	if (!panel->backlight.edp.vesa.info.aux_set) {
++		const u32 pwm_level = intel_backlight_level_to_pwm(connector, level);
++
++		intel_backlight_set_pwm_level(conn_state, pwm_level);
++	}
++
+ 	drm_edp_backlight_set_level(&intel_dp->aux, &panel->backlight.edp.vesa.info, level);
+ }
+ 
+@@ -294,8 +300,13 @@ intel_dp_aux_vesa_enable_backlight(const struct intel_crtc_state *crtc_state,
+ 	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+ 
+ 	if (!panel->backlight.edp.vesa.info.aux_enable) {
+-		u32 pwm_level = intel_backlight_invert_pwm_level(connector,
+-								 panel->backlight.pwm_level_max);
++		u32 pwm_level;
++
++		if (!panel->backlight.edp.vesa.info.aux_set)
++			pwm_level = intel_backlight_level_to_pwm(connector, level);
++		else
++			pwm_level = intel_backlight_invert_pwm_level(connector,
++								     panel->backlight.pwm_level_max);
+ 
+ 		panel->backlight.pwm_funcs->enable(crtc_state, conn_state, pwm_level);
+ 	}
+@@ -332,7 +343,7 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
+ 	if (ret < 0)
+ 		return ret;
+ 
+-	if (!panel->backlight.edp.vesa.info.aux_enable) {
++	if (!panel->backlight.edp.vesa.info.aux_set || !panel->backlight.edp.vesa.info.aux_enable) {
+ 		ret = panel->backlight.pwm_funcs->setup(connector, pipe);
+ 		if (ret < 0) {
+ 			drm_err(&i915->drm,
+@@ -341,14 +352,27 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
+ 			return ret;
+ 		}
+ 	}
+-	panel->backlight.max = panel->backlight.edp.vesa.info.max;
+-	panel->backlight.min = 0;
+-	if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
+-		panel->backlight.level = current_level;
+-		panel->backlight.enabled = panel->backlight.level != 0;
++
++	if (panel->backlight.edp.vesa.info.aux_set) {
++		panel->backlight.max = panel->backlight.edp.vesa.info.max;
++		panel->backlight.min = 0;
++		if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
++			panel->backlight.level = current_level;
++			panel->backlight.enabled = panel->backlight.level != 0;
++		} else {
++			panel->backlight.level = panel->backlight.max;
++			panel->backlight.enabled = false;
++		}
+ 	} else {
+-		panel->backlight.level = panel->backlight.max;
+-		panel->backlight.enabled = false;
++		panel->backlight.max = panel->backlight.pwm_level_max;
++		panel->backlight.min = panel->backlight.pwm_level_min;
++		if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_PWM) {
++			panel->backlight.level = panel->backlight.pwm_funcs->get(connector, pipe);
++			panel->backlight.enabled = panel->backlight.pwm_enabled;
++		} else {
++			panel->backlight.level = panel->backlight.max;
++			panel->backlight.enabled = false;
++		}
+ 	}
+ 
+ 	return 0;
+diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
+index afdf7f4183f9..8b2ed4199284 100644
+--- a/include/drm/drm_dp_helper.h
++++ b/include/drm/drm_dp_helper.h
+@@ -1868,7 +1868,7 @@ drm_dp_sink_can_do_video_without_timing_msa(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+  *
+  * Note that currently this function will return %false for panels which support various DPCD
+  * backlight features but which require the brightness be set through PWM, and don't support setting
+- * the brightness level via the DPCD. This is a TODO.
++ * the brightness level via the DPCD.
+  *
+  * Returns: %True if @edp_dpcd indicates that VESA backlight controls are supported, %false
+  * otherwise
+@@ -1876,8 +1876,7 @@ drm_dp_sink_can_do_video_without_timing_msa(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+ static inline bool
+ drm_edp_backlight_supported(const u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE])
+ {
+-	return (edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) &&
+-		(edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP);
++	return !!(edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP);
+ }
+ 
+ /*
+@@ -2238,6 +2237,7 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, enum drm_dp_quirk quirk)
+  * @max: The maximum backlight level that may be set
+  * @lsb_reg_used: Do we also write values to the DP_EDP_BACKLIGHT_BRIGHTNESS_LSB register?
+  * @aux_enable: Does the panel support the AUX enable cap?
++ * @aux_set: Does the panel support setting the brightness through AUX?
+  *
+  * This structure contains various data about an eDP backlight, which can be populated by using
+  * drm_edp_backlight_init().
+@@ -2249,6 +2249,7 @@ struct drm_edp_backlight_info {
+ 
+ 	bool lsb_reg_used : 1;
+ 	bool aux_enable : 1;
++	bool aux_set : 1;
+ };
+ 
+ int
+
+From patchwork Fri Nov  5 18:33:42 2021
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
+Subject: [v5,5/5] drm/i915: Clarify probing order in
+ intel_dp_aux_init_backlight_funcs()
+From: Lyude Paul <lyude@redhat.com>
+X-Patchwork-Id: 462382
+Message-Id: <20211105183342.130810-6-lyude@redhat.com>
+To: dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
+ intel-gfx@lists.freedesktop.org
+Cc: David Airlie <airlied@linux.ie>, open list <linux-kernel@vger.kernel.org>
+Date: Fri,  5 Nov 2021 14:33:42 -0400
+
+Hooray! We've managed to hit enough bugs upstream that I've been able to
+come up with a pretty solid explanation for how backlight controls are
+actually supposed to be detected and used these days. As well, having the
+rest of the PWM bits in VESA's backlight interface implemented seems to
+have fixed all of the problematic brightness controls laptop panels that
+we've hit so far.
+
+So, let's actually document this instead of just calling the laptop panels
+liars. As well, I would like to formally apologize to all of the laptop
+panels I called liars. I'm sorry laptop panels, hopefully you can all
+forgive me and we can move past this~
+
+Signed-off-by: Lyude Paul <lyude@redhat.com>
+Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
+---
+ .../drm/i915/display/intel_dp_aux_backlight.c    | 16 +++++++++++-----
+ 1 file changed, 11 insertions(+), 5 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 96fe3eaba44a..8b9c925c4c16 100644
+--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
++++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+@@ -456,11 +456,17 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
+ 	}
+ 
+ 	/*
+-	 * A lot of eDP panels in the wild will report supporting both the
+-	 * Intel proprietary backlight control interface, and the VESA
+-	 * backlight control interface. Many of these panels are liars though,
+-	 * and will only work with the Intel interface. So, always probe for
+-	 * that first.
++	 * Since Intel has their own backlight control interface, the majority of machines out there
++	 * using DPCD backlight controls with Intel GPUs will be using this interface as opposed to
++	 * the VESA interface. However, other GPUs (such as Nvidia's) will always use the VESA
++	 * interface. This means that there's quite a number of panels out there that will advertise
++	 * support for both interfaces, primarily systems with Intel/Nvidia hybrid GPU setups.
++	 *
++	 * There's a catch to this though: on many panels that advertise support for both
++	 * interfaces, the VESA backlight interface will stop working once we've programmed the
++	 * panel with Intel's OUI - which is also required for us to be able to detect Intel's
++	 * backlight interface at all. This means that the only sensible way for us to detect both
++	 * interfaces is to probe for Intel's first, and VESA's second.
+ 	 */
+ 	if (try_intel_interface && intel_dp_aux_supports_hdr_backlight(connector)) {
+ 		drm_dbg_kms(dev, "Using Intel proprietary eDP backlight controls\n");