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* [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD"
@ 2017-07-04 15:00 David Weinehall
  2017-07-04 16:23 ` ✓ Fi.CI.BAT: success for " Patchwork
  2017-07-05 10:03 ` [PATCH] " Jani Nikula
  0 siblings, 2 replies; 5+ messages in thread
From: David Weinehall @ 2017-07-04 15:00 UTC (permalink / raw)
  To: intel-gfx; +Cc: jani.nikula

This reverts commit ae25eceab616d16a07bcaa434b84463d58a3bdc3.

The introduction of dynamic backlight control causes
Lenovo ThinkPad X1 Carbon 4th Gen to boot to a black screen;
presumably the backlight is off.

Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_params.c            |  5 -----
 drivers/gpu/drm/i915/i915_params.h            |  3 +--
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 26 --------------------------
 3 files changed, 1 insertion(+), 33 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 88b9d3e6713a..5b5ab15d191f 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -65,7 +65,6 @@ struct i915_params i915 __read_mostly = {
 	.inject_load_failure = 0,
 	.enable_dpcd_backlight = -1,
 	.enable_gvt = false,
-	.enable_dbc = true,
 };
 
 module_param_named(modeset, i915.modeset, int, 0400);
@@ -255,7 +254,3 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
 module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
 MODULE_PARM_DESC(enable_gvt,
 	"Enable support for Intel GVT-g graphics virtualization host support(default:false)");
-
-module_param_named_unsafe(enable_dbc, i915.enable_dbc, bool, 0600);
-MODULE_PARM_DESC(enable_dbc,
-	"Enable support for dynamic backlight control (default:true)");
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 057e203e6bda..0d6cf9138dc4 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -67,8 +67,7 @@
 	func(bool, verbose_state_checks); \
 	func(bool, nuclear_pageflip); \
 	func(bool, enable_dp_mst); \
-	func(bool, enable_gvt); \
-	func(bool, enable_dbc)
+	func(bool, enable_gvt)
 
 #define MEMBER(T, member) T member
 struct i915_params {
diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index b25cd88fc1c5..fea161727c6e 100644
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -173,24 +173,6 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
 	return true;
 }
 
-/*
-* Set minimum / maximum dynamic brightness percentage. This value is expressed
-* as the percentage of normal brightness in 5% increments.
-*/
-static bool
-intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
-					   u32 min, u32 max)
-{
-	u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5) };
-
-	if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
-			  dbc, sizeof(dbc)) < 0) {
-		DRM_DEBUG_KMS("Failed to write aux DBC brightness level\n");
-		return false;
-	}
-	return true;
-}
-
 static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_state,
 					  const struct drm_connector_state *conn_state)
 {
@@ -226,14 +208,6 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
 		if (intel_dp_aux_set_pwm_freq(connector))
 			new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
 
-	if (i915.enable_dbc &&
-	    (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP)) {
-		if(intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100)) {
-			new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
-			DRM_DEBUG_KMS("Enable dynamic brightness.\n");
-		}
-	}
-
 	if (new_dpcd_buf != dpcd_buf) {
 		if (drm_dp_dpcd_writeb(&intel_dp->aux,
 			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
-- 
2.13.2

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* ✓ Fi.CI.BAT: success for Revert "drm/i915: Add option to support dynamic backlight via DPCD"
  2017-07-04 15:00 [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD" David Weinehall
@ 2017-07-04 16:23 ` Patchwork
  2017-07-05 10:03 ` [PATCH] " Jani Nikula
  1 sibling, 0 replies; 5+ messages in thread
From: Patchwork @ 2017-07-04 16:23 UTC (permalink / raw)
  To: David Weinehall; +Cc: intel-gfx

== Series Details ==

Series: Revert "drm/i915: Add option to support dynamic backlight via DPCD"
URL   : https://patchwork.freedesktop.org/series/26818/
State : success

== Summary ==

Series 26818v1 Revert "drm/i915: Add option to support dynamic backlight via DPCD"
https://patchwork.freedesktop.org/api/1.0/series/26818/revisions/1/mbox/

Test gem_exec_suspend:
        Subgroup basic-s4-devices:
                dmesg-warn -> PASS       (fi-kbl-r) fdo#100125
Test kms_busy:
        Subgroup basic-flip-default-b:
                dmesg-warn -> PASS       (fi-skl-6700hq) fdo#101144
Test kms_pipe_crc_basic:
        Subgroup hang-read-crc-pipe-a:
                dmesg-warn -> PASS       (fi-pnv-d510) fdo#101597
        Subgroup suspend-read-crc-pipe-b:
                dmesg-warn -> PASS       (fi-byt-j1900) fdo#101516

fdo#100125 https://bugs.freedesktop.org/show_bug.cgi?id=100125
fdo#101144 https://bugs.freedesktop.org/show_bug.cgi?id=101144
fdo#101597 https://bugs.freedesktop.org/show_bug.cgi?id=101597
fdo#101516 https://bugs.freedesktop.org/show_bug.cgi?id=101516

fi-bdw-5557u     total:279  pass:268  dwarn:0   dfail:0   fail:0   skip:11  time:441s
fi-bdw-gvtdvm    total:279  pass:257  dwarn:8   dfail:0   fail:0   skip:14  time:429s
fi-blb-e6850     total:279  pass:224  dwarn:1   dfail:0   fail:0   skip:54  time:352s
fi-bsw-n3050     total:279  pass:243  dwarn:0   dfail:0   fail:0   skip:36  time:530s
fi-bxt-j4205     total:279  pass:260  dwarn:0   dfail:0   fail:0   skip:19  time:511s
fi-byt-j1900     total:279  pass:255  dwarn:0   dfail:0   fail:0   skip:24  time:486s
fi-byt-n2820     total:279  pass:250  dwarn:1   dfail:0   fail:0   skip:28  time:483s
fi-glk-2a        total:279  pass:260  dwarn:0   dfail:0   fail:0   skip:19  time:594s
fi-hsw-4770      total:279  pass:263  dwarn:0   dfail:0   fail:0   skip:16  time:438s
fi-hsw-4770r     total:279  pass:263  dwarn:0   dfail:0   fail:0   skip:16  time:414s
fi-ilk-650       total:279  pass:229  dwarn:0   dfail:0   fail:0   skip:50  time:427s
fi-ivb-3520m     total:279  pass:261  dwarn:0   dfail:0   fail:0   skip:18  time:495s
fi-ivb-3770      total:279  pass:261  dwarn:0   dfail:0   fail:0   skip:18  time:478s
fi-kbl-7500u     total:279  pass:261  dwarn:0   dfail:0   fail:0   skip:18  time:471s
fi-kbl-7560u     total:279  pass:268  dwarn:1   dfail:0   fail:0   skip:10  time:572s
fi-kbl-r         total:279  pass:261  dwarn:0   dfail:0   fail:0   skip:18  time:583s
fi-pnv-d510      total:279  pass:222  dwarn:2   dfail:0   fail:0   skip:55  time:556s
fi-skl-6260u     total:279  pass:269  dwarn:0   dfail:0   fail:0   skip:10  time:455s
fi-skl-6700hq    total:279  pass:262  dwarn:0   dfail:0   fail:0   skip:17  time:587s
fi-skl-6700k     total:279  pass:257  dwarn:4   dfail:0   fail:0   skip:18  time:477s
fi-skl-6770hq    total:279  pass:269  dwarn:0   dfail:0   fail:0   skip:10  time:476s
fi-skl-gvtdvm    total:279  pass:266  dwarn:0   dfail:0   fail:0   skip:13  time:439s
fi-snb-2520m     total:279  pass:251  dwarn:0   dfail:0   fail:0   skip:28  time:550s
fi-snb-2600      total:279  pass:250  dwarn:0   dfail:0   fail:0   skip:29  time:406s

24346e831017070c18f3c33b74a7b098682e20f7 drm-tip: 2017y-07m-04d-15h-39m-34s UTC integration manifest
08aa0a5c Revert "drm/i915: Add option to support dynamic backlight via DPCD"

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_5107/
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD"
  2017-07-04 15:00 [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD" David Weinehall
  2017-07-04 16:23 ` ✓ Fi.CI.BAT: success for " Patchwork
@ 2017-07-05 10:03 ` Jani Nikula
  2017-07-05 14:40   ` David Weinehall
  1 sibling, 1 reply; 5+ messages in thread
From: Jani Nikula @ 2017-07-05 10:03 UTC (permalink / raw)
  To: David Weinehall, intel-gfx

On Tue, 04 Jul 2017, David Weinehall <david.weinehall@linux.intel.com> wrote:
> This reverts commit ae25eceab616d16a07bcaa434b84463d58a3bdc3.
>
> The introduction of dynamic backlight control causes
> Lenovo ThinkPad X1 Carbon 4th Gen to boot to a black screen;
> presumably the backlight is off.

Oh, I thought reverting just this commit was not enough for you, based
on the previous discussion in the patch thread. If this is enough, and
the DPCD backlight by default works for you, I might be inclined to go
with just defaulting to false here.

BR,
Jani.


>
> Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_params.c            |  5 -----
>  drivers/gpu/drm/i915/i915_params.h            |  3 +--
>  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 26 --------------------------
>  3 files changed, 1 insertion(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 88b9d3e6713a..5b5ab15d191f 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -65,7 +65,6 @@ struct i915_params i915 __read_mostly = {
>  	.inject_load_failure = 0,
>  	.enable_dpcd_backlight = -1,
>  	.enable_gvt = false,
> -	.enable_dbc = true,
>  };
>  
>  module_param_named(modeset, i915.modeset, int, 0400);
> @@ -255,7 +254,3 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
>  module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
>  MODULE_PARM_DESC(enable_gvt,
>  	"Enable support for Intel GVT-g graphics virtualization host support(default:false)");
> -
> -module_param_named_unsafe(enable_dbc, i915.enable_dbc, bool, 0600);
> -MODULE_PARM_DESC(enable_dbc,
> -	"Enable support for dynamic backlight control (default:true)");
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index 057e203e6bda..0d6cf9138dc4 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -67,8 +67,7 @@
>  	func(bool, verbose_state_checks); \
>  	func(bool, nuclear_pageflip); \
>  	func(bool, enable_dp_mst); \
> -	func(bool, enable_gvt); \
> -	func(bool, enable_dbc)
> +	func(bool, enable_gvt)
>  
>  #define MEMBER(T, member) T member
>  struct i915_params {
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> index b25cd88fc1c5..fea161727c6e 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -173,24 +173,6 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
>  	return true;
>  }
>  
> -/*
> -* Set minimum / maximum dynamic brightness percentage. This value is expressed
> -* as the percentage of normal brightness in 5% increments.
> -*/
> -static bool
> -intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
> -					   u32 min, u32 max)
> -{
> -	u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5) };
> -
> -	if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
> -			  dbc, sizeof(dbc)) < 0) {
> -		DRM_DEBUG_KMS("Failed to write aux DBC brightness level\n");
> -		return false;
> -	}
> -	return true;
> -}
> -
>  static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_state,
>  					  const struct drm_connector_state *conn_state)
>  {
> @@ -226,14 +208,6 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
>  		if (intel_dp_aux_set_pwm_freq(connector))
>  			new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
>  
> -	if (i915.enable_dbc &&
> -	    (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP)) {
> -		if(intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100)) {
> -			new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
> -			DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> -		}
> -	}
> -
>  	if (new_dpcd_buf != dpcd_buf) {
>  		if (drm_dp_dpcd_writeb(&intel_dp->aux,
>  			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {

-- 
Jani Nikula, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD"
  2017-07-05 10:03 ` [PATCH] " Jani Nikula
@ 2017-07-05 14:40   ` David Weinehall
  2017-07-06 13:53     ` David Weinehall
  0 siblings, 1 reply; 5+ messages in thread
From: David Weinehall @ 2017-07-05 14:40 UTC (permalink / raw)
  To: Jani Nikula; +Cc: intel-gfx

On Wed, Jul 05, 2017 at 01:03:46PM +0300, Jani Nikula wrote:
> On Tue, 04 Jul 2017, David Weinehall <david.weinehall@linux.intel.com> wrote:
> > This reverts commit ae25eceab616d16a07bcaa434b84463d58a3bdc3.
> >
> > The introduction of dynamic backlight control causes
> > Lenovo ThinkPad X1 Carbon 4th Gen to boot to a black screen;
> > presumably the backlight is off.
> 
> Oh, I thought reverting just this commit was not enough for you, based
> on the previous discussion in the patch thread. If this is enough, and
> the DPCD backlight by default works for you, I might be inclined to go
> with just defaulting to false here.

Yeah, that was indeed my experience, but I cannot reproduce that
behaviour now; disabling DBC seems to be enough to make things work.
It might be that I made some mistake in my earlier testing.

I retested now, with the following results:

Both DPCD & DBC enabled: black screen
DBC enabled, DPCD disabled: works
DBC disabled, DPCD enabled: works
DBC disabled, DPCD disabled: works

Based on my understanding of the code, DPCD backlight is required for
DBC to work, so it makes sense that disabling either of the two
makes things work (hence I don't understand how I got my earlier
result where just disabling DBC wasn't enough).

Anyhow, I'm fine with just changing the default to false.


Kind regards, David

> BR,
> Jani.
> 
> 
> >
> > Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_params.c            |  5 -----
> >  drivers/gpu/drm/i915/i915_params.h            |  3 +--
> >  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 26 --------------------------
> >  3 files changed, 1 insertion(+), 33 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> > index 88b9d3e6713a..5b5ab15d191f 100644
> > --- a/drivers/gpu/drm/i915/i915_params.c
> > +++ b/drivers/gpu/drm/i915/i915_params.c
> > @@ -65,7 +65,6 @@ struct i915_params i915 __read_mostly = {
> >  	.inject_load_failure = 0,
> >  	.enable_dpcd_backlight = -1,
> >  	.enable_gvt = false,
> > -	.enable_dbc = true,
> >  };
> >  
> >  module_param_named(modeset, i915.modeset, int, 0400);
> > @@ -255,7 +254,3 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
> >  module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
> >  MODULE_PARM_DESC(enable_gvt,
> >  	"Enable support for Intel GVT-g graphics virtualization host support(default:false)");
> > -
> > -module_param_named_unsafe(enable_dbc, i915.enable_dbc, bool, 0600);
> > -MODULE_PARM_DESC(enable_dbc,
> > -	"Enable support for dynamic backlight control (default:true)");
> > diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> > index 057e203e6bda..0d6cf9138dc4 100644
> > --- a/drivers/gpu/drm/i915/i915_params.h
> > +++ b/drivers/gpu/drm/i915/i915_params.h
> > @@ -67,8 +67,7 @@
> >  	func(bool, verbose_state_checks); \
> >  	func(bool, nuclear_pageflip); \
> >  	func(bool, enable_dp_mst); \
> > -	func(bool, enable_gvt); \
> > -	func(bool, enable_dbc)
> > +	func(bool, enable_gvt)
> >  
> >  #define MEMBER(T, member) T member
> >  struct i915_params {
> > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > index b25cd88fc1c5..fea161727c6e 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > @@ -173,24 +173,6 @@ static bool intel_dp_aux_set_pwm_freq(struct intel_connector *connector)
> >  	return true;
> >  }
> >  
> > -/*
> > -* Set minimum / maximum dynamic brightness percentage. This value is expressed
> > -* as the percentage of normal brightness in 5% increments.
> > -*/
> > -static bool
> > -intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
> > -					   u32 min, u32 max)
> > -{
> > -	u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5) };
> > -
> > -	if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
> > -			  dbc, sizeof(dbc)) < 0) {
> > -		DRM_DEBUG_KMS("Failed to write aux DBC brightness level\n");
> > -		return false;
> > -	}
> > -	return true;
> > -}
> > -
> >  static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_state,
> >  					  const struct drm_connector_state *conn_state)
> >  {
> > @@ -226,14 +208,6 @@ static void intel_dp_aux_enable_backlight(const struct intel_crtc_state *crtc_st
> >  		if (intel_dp_aux_set_pwm_freq(connector))
> >  			new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> >  
> > -	if (i915.enable_dbc &&
> > -	    (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP)) {
> > -		if(intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100)) {
> > -			new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
> > -			DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> > -		}
> > -	}
> > -
> >  	if (new_dpcd_buf != dpcd_buf) {
> >  		if (drm_dp_dpcd_writeb(&intel_dp->aux,
> >  			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD"
  2017-07-05 14:40   ` David Weinehall
@ 2017-07-06 13:53     ` David Weinehall
  0 siblings, 0 replies; 5+ messages in thread
From: David Weinehall @ 2017-07-06 13:53 UTC (permalink / raw)
  To: Jani Nikula, intel-gfx

On Wed, Jul 05, 2017 at 05:40:19PM +0300, David Weinehall wrote:
> On Wed, Jul 05, 2017 at 01:03:46PM +0300, Jani Nikula wrote:
> > On Tue, 04 Jul 2017, David Weinehall <david.weinehall@linux.intel.com> wrote:
> > > This reverts commit ae25eceab616d16a07bcaa434b84463d58a3bdc3.
> > >
> > > The introduction of dynamic backlight control causes
> > > Lenovo ThinkPad X1 Carbon 4th Gen to boot to a black screen;
> > > presumably the backlight is off.
> > 
> > Oh, I thought reverting just this commit was not enough for you, based
> > on the previous discussion in the patch thread. If this is enough, and
> > the DPCD backlight by default works for you, I might be inclined to go
> > with just defaulting to false here.
> 
> Yeah, that was indeed my experience, but I cannot reproduce that
> behaviour now; disabling DBC seems to be enough to make things work.
> It might be that I made some mistake in my earlier testing.
> 
> I retested now, with the following results:
> 
> Both DPCD & DBC enabled: black screen
> DBC enabled, DPCD disabled: works
> DBC disabled, DPCD enabled: works
> DBC disabled, DPCD disabled: works
> 
> Based on my understanding of the code, DPCD backlight is required for
> DBC to work, so it makes sense that disabling either of the two
> makes things work (hence I don't understand how I got my earlier
> result where just disabling DBC wasn't enough).
> 
> Anyhow, I'm fine with just changing the default to false.

I need to NAK my own revert. It turns out that while booting with
only i915.enable_dbc=0 gives backlight, the backlight will only work
until a suspend/resume cycle has taken place; after that the display
will come up blank, unless i915.enable_dpcd_backlight=0 is also
passed.

So I'll submit a new revert.


Kind regards, David
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^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-07-06 13:53 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-07-04 15:00 [PATCH] Revert "drm/i915: Add option to support dynamic backlight via DPCD" David Weinehall
2017-07-04 16:23 ` ✓ Fi.CI.BAT: success for " Patchwork
2017-07-05 10:03 ` [PATCH] " Jani Nikula
2017-07-05 14:40   ` David Weinehall
2017-07-06 13:53     ` David Weinehall

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