diff mbox series

drm/i915/dp: Tweak initial dpcd backlight.enabled value

Message ID 20200918002845.32766-1-sean@poorly.run
State New, archived
Headers show
Series drm/i915/dp: Tweak initial dpcd backlight.enabled value | expand

Commit Message

Sean Paul Sept. 18, 2020, 12:28 a.m. UTC
From: Sean Paul <seanpaul@chromium.org>

In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
DPCD control mode"), we fixed the brightness level when DPCD control was
not active to max brightness. This is as good as we can guess since most
backlights go on full when uncontrolled.

However in doing so we changed the semantics of the initial
'backlight.enabled' value. At least on Pixelbooks, they  were relying
on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
boot such that enabled would be false. This causes the device to be
enabled when the brightness is set. Without this, brightness control
doesn't work. So by changing brightness to max, we also flipped enabled
to be true on boot.

To fix this, make enabled a function of brightness and backlight control
mechanism.

Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in DPCD control mode")
Cc: Lyude Paul <lyude@redhat.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Kevin Chowski <chowski@chromium.org>>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
---
 .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++-------
 1 file changed, 20 insertions(+), 11 deletions(-)

Comments

Lyude Paul Sept. 21, 2020, 10:35 p.m. UTC | #1
So if I understand this correctly, it sounds like that some Pixelbooks boot up
with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without the
panel actually having DPCD backlight controls enabled?

If I'm understanding that correctly, then this patch looks good to me:

Reviewed-by: Lyude Paul <lyude@redhat.com>

On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> From: Sean Paul <seanpaul@chromium.org>
> 
> In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> DPCD control mode"), we fixed the brightness level when DPCD control was
> not active to max brightness. This is as good as we can guess since most
> backlights go on full when uncontrolled.
> 
> However in doing so we changed the semantics of the initial
> 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> boot such that enabled would be false. This causes the device to be
> enabled when the brightness is set. Without this, brightness control
> doesn't work. So by changing brightness to max, we also flipped enabled
> to be true on boot.
> 
> To fix this, make enabled a function of brightness and backlight control
> mechanism.
> 
> Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in DPCD
> control mode")
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Kevin Chowski <chowski@chromium.org>>
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++-------
>  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct intel_dp
> *intel_dp, bool enable)
>  	}
>  }
>  
> -/*
> - * Read the current backlight value from DPCD register(s) based
> - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> - */
> -static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
> +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> *connector)
>  {
>  	struct intel_dp *intel_dp = intel_attached_dp(connector);
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> -	u8 read_val[2] = { 0x0 };
>  	u8 mode_reg;
> -	u16 level = 0;
>  
>  	if (drm_dp_dpcd_readb(&intel_dp->aux,
>  			      DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> intel_connector *connector)
>  		drm_dbg_kms(&i915->drm,
>  			    "Failed to read the DPCD register 0x%x\n",
>  			    DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> -		return 0;
> +		return false;
>  	}
>  
> +	return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> +	       DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> +}
> +
> +/*
> + * Read the current backlight value from DPCD register(s) based
> + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> + */
> +static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
> +{
> +	struct intel_dp *intel_dp = intel_attached_dp(connector);
> +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +	u8 read_val[2] = { 0x0 };
> +	u16 level = 0;
> +
>  	/*
>  	 * If we're not in DPCD control mode yet, the programmed brightness
>  	 * value is meaningless and we should assume max brightness
>  	 */
> -	if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> -	    DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> +	if (!intel_dp_aux_backlight_dpcd_mode(connector))
>  		return connector->panel.backlight.max;
>  
>  	if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> intel_connector *connector,
>  
>  	panel->backlight.min = 0;
>  	panel->backlight.level = intel_dp_aux_get_backlight(connector);
> -	panel->backlight.enabled = panel->backlight.level != 0;
> +	panel->backlight.enabled = intel_dp_aux_backlight_dpcd_mode(connector)
> &&
> +				   panel->backlight.level != 0;
>  
>  	return 0;
>  }
Sean Paul Sept. 22, 2020, 1:39 p.m. UTC | #2
On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
>
> So if I understand this correctly, it sounds like that some Pixelbooks boot up
> with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without the
> panel actually having DPCD backlight controls enabled?

It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
backlight.enabled = false. By changing backlight.level = max,
backlight.enabled is now set to true. This results in losing backlight
control on boot (since the enable routine is no longer invoked).

Sean

>
> If I'm understanding that correctly, then this patch looks good to me:
>
> Reviewed-by: Lyude Paul <lyude@redhat.com>
>
> On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > From: Sean Paul <seanpaul@chromium.org>
> >
> > In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> > DPCD control mode"), we fixed the brightness level when DPCD control was
> > not active to max brightness. This is as good as we can guess since most
> > backlights go on full when uncontrolled.
> >
> > However in doing so we changed the semantics of the initial
> > 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> > boot such that enabled would be false. This causes the device to be
> > enabled when the brightness is set. Without this, brightness control
> > doesn't work. So by changing brightness to max, we also flipped enabled
> > to be true on boot.
> >
> > To fix this, make enabled a function of brightness and backlight control
> > mechanism.
> >
> > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in DPCD
> > control mode")
> > Cc: Lyude Paul <lyude@redhat.com>
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Kevin Chowski <chowski@chromium.org>>
> > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > ---
> >  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++-------
> >  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct intel_dp
> > *intel_dp, bool enable)
> >       }
> >  }
> >
> > -/*
> > - * Read the current backlight value from DPCD register(s) based
> > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > - */
> > -static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
> > +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> > *connector)
> >  {
> >       struct intel_dp *intel_dp = intel_attached_dp(connector);
> >       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > -     u8 read_val[2] = { 0x0 };
> >       u8 mode_reg;
> > -     u16 level = 0;
> >
> >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> >                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > intel_connector *connector)
> >               drm_dbg_kms(&i915->drm,
> >                           "Failed to read the DPCD register 0x%x\n",
> >                           DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > -             return 0;
> > +             return false;
> >       }
> >
> > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > +}
> > +
> > +/*
> > + * Read the current backlight value from DPCD register(s) based
> > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > + */
> > +static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
> > +{
> > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > +     u8 read_val[2] = { 0x0 };
> > +     u16 level = 0;
> > +
> >       /*
> >        * If we're not in DPCD control mode yet, the programmed brightness
> >        * value is meaningless and we should assume max brightness
> >        */
> > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> >               return connector->panel.backlight.max;
> >
> >       if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > intel_connector *connector,
> >
> >       panel->backlight.min = 0;
> >       panel->backlight.level = intel_dp_aux_get_backlight(connector);
> > -     panel->backlight.enabled = panel->backlight.level != 0;
> > +     panel->backlight.enabled = intel_dp_aux_backlight_dpcd_mode(connector)
> > &&
> > +                                panel->backlight.level != 0;
> >
> >       return 0;
> >  }
> --
> Cheers,
>         Lyude Paul (she/her)
>         Software Engineer at Red Hat
>
Lyude Paul Sept. 22, 2020, 3:36 p.m. UTC | #3
On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
> On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
> > So if I understand this correctly, it sounds like that some Pixelbooks
> > boot up
> > with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without the
> > panel actually having DPCD backlight controls enabled?
> 
> It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
> backlight.enabled = false. By changing backlight.level = max,
> backlight.enabled is now set to true. This results in losing backlight
> control on boot (since the enable routine is no longer invoked).
> 
Ahhh ok, I'm fine with that - review still stands :)

> Sean
> 
> > If I'm understanding that correctly, then this patch looks good to me:
> > 
> > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > 
> > On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > > From: Sean Paul <seanpaul@chromium.org>
> > > 
> > > In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > DPCD control mode"), we fixed the brightness level when DPCD control was
> > > not active to max brightness. This is as good as we can guess since most
> > > backlights go on full when uncontrolled.
> > > 
> > > However in doing so we changed the semantics of the initial
> > > 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> > > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> > > boot such that enabled would be false. This causes the device to be
> > > enabled when the brightness is set. Without this, brightness control
> > > doesn't work. So by changing brightness to max, we also flipped enabled
> > > to be true on boot.
> > > 
> > > To fix this, make enabled a function of brightness and backlight control
> > > mechanism.
> > > 
> > > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in DPCD
> > > control mode")
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > Cc: Kevin Chowski <chowski@chromium.org>>
> > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > ---
> > >  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++-------
> > >  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct intel_dp
> > > *intel_dp, bool enable)
> > >       }
> > >  }
> > > 
> > > -/*
> > > - * Read the current backlight value from DPCD register(s) based
> > > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > - */
> > > -static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > *connector)
> > > +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> > > *connector)
> > >  {
> > >       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > >       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > -     u8 read_val[2] = { 0x0 };
> > >       u8 mode_reg;
> > > -     u16 level = 0;
> > > 
> > >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> > >                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > > intel_connector *connector)
> > >               drm_dbg_kms(&i915->drm,
> > >                           "Failed to read the DPCD register 0x%x\n",
> > >                           DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > > -             return 0;
> > > +             return false;
> > >       }
> > > 
> > > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > > +}
> > > +
> > > +/*
> > > + * Read the current backlight value from DPCD register(s) based
> > > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > + */
> > > +static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > *connector)
> > > +{
> > > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > +     u8 read_val[2] = { 0x0 };
> > > +     u16 level = 0;
> > > +
> > >       /*
> > >        * If we're not in DPCD control mode yet, the programmed
> > > brightness
> > >        * value is meaningless and we should assume max brightness
> > >        */
> > > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> > >               return connector->panel.backlight.max;
> > > 
> > >       if (drm_dp_dpcd_read(&intel_dp->aux,
> > > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > > intel_connector *connector,
> > > 
> > >       panel->backlight.min = 0;
> > >       panel->backlight.level = intel_dp_aux_get_backlight(connector);
> > > -     panel->backlight.enabled = panel->backlight.level != 0;
> > > +     panel->backlight.enabled =
> > > intel_dp_aux_backlight_dpcd_mode(connector)
> > > &&
> > > +                                panel->backlight.level != 0;
> > > 
> > >       return 0;
> > >  }
> > --
> > Cheers,
> >         Lyude Paul (she/her)
> >         Software Engineer at Red Hat
> >
Sean Paul Oct. 12, 2020, 5:50 p.m. UTC | #4
On Tue, Sep 22, 2020 at 11:36 AM Lyude Paul <lyude@redhat.com> wrote:
>
> On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
> > On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
> > > So if I understand this correctly, it sounds like that some Pixelbooks
> > > boot up
> > > with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without the
> > > panel actually having DPCD backlight controls enabled?
> >
> > It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
> > backlight.enabled = false. By changing backlight.level = max,
> > backlight.enabled is now set to true. This results in losing backlight
> > control on boot (since the enable routine is no longer invoked).
> >
> Ahhh ok, I'm fine with that - review still stands :)

Pinging intel maintainers, could someone please apply this?


Sean

>
> > Sean
> >
> > > If I'm understanding that correctly, then this patch looks good to me:
> > >
> > > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > >
> > > On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > > > From: Sean Paul <seanpaul@chromium.org>
> > > >
> > > > In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > DPCD control mode"), we fixed the brightness level when DPCD control was
> > > > not active to max brightness. This is as good as we can guess since most
> > > > backlights go on full when uncontrolled.
> > > >
> > > > However in doing so we changed the semantics of the initial
> > > > 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> > > > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> > > > boot such that enabled would be false. This causes the device to be
> > > > enabled when the brightness is set. Without this, brightness control
> > > > doesn't work. So by changing brightness to max, we also flipped enabled
> > > > to be true on boot.
> > > >
> > > > To fix this, make enabled a function of brightness and backlight control
> > > > mechanism.
> > > >
> > > > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in DPCD
> > > > control mode")
> > > > Cc: Lyude Paul <lyude@redhat.com>
> > > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > > Cc: Kevin Chowski <chowski@chromium.org>>
> > > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > > ---
> > > >  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++-------
> > > >  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct intel_dp
> > > > *intel_dp, bool enable)
> > > >       }
> > > >  }
> > > >
> > > > -/*
> > > > - * Read the current backlight value from DPCD register(s) based
> > > > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > - */
> > > > -static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > *connector)
> > > > +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> > > > *connector)
> > > >  {
> > > >       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > >       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > -     u8 read_val[2] = { 0x0 };
> > > >       u8 mode_reg;
> > > > -     u16 level = 0;
> > > >
> > > >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> > > >                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > > > intel_connector *connector)
> > > >               drm_dbg_kms(&i915->drm,
> > > >                           "Failed to read the DPCD register 0x%x\n",
> > > >                           DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > > > -             return 0;
> > > > +             return false;
> > > >       }
> > > >
> > > > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > > > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > > > +}
> > > > +
> > > > +/*
> > > > + * Read the current backlight value from DPCD register(s) based
> > > > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > + */
> > > > +static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > *connector)
> > > > +{
> > > > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > +     u8 read_val[2] = { 0x0 };
> > > > +     u16 level = 0;
> > > > +
> > > >       /*
> > > >        * If we're not in DPCD control mode yet, the programmed
> > > > brightness
> > > >        * value is meaningless and we should assume max brightness
> > > >        */
> > > > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > > > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > > > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> > > >               return connector->panel.backlight.max;
> > > >
> > > >       if (drm_dp_dpcd_read(&intel_dp->aux,
> > > > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > > > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > > > intel_connector *connector,
> > > >
> > > >       panel->backlight.min = 0;
> > > >       panel->backlight.level = intel_dp_aux_get_backlight(connector);
> > > > -     panel->backlight.enabled = panel->backlight.level != 0;
> > > > +     panel->backlight.enabled =
> > > > intel_dp_aux_backlight_dpcd_mode(connector)
> > > > &&
> > > > +                                panel->backlight.level != 0;
> > > >
> > > >       return 0;
> > > >  }
> > > --
> > > Cheers,
> > >         Lyude Paul (she/her)
> > >         Software Engineer at Red Hat
> > >
> --
> Cheers,
>         Lyude Paul (she/her)
>         Software Engineer at Red Hat
>
Lyude Paul Oct. 12, 2020, 6:52 p.m. UTC | #5
On Mon, 2020-10-12 at 13:50 -0400, Sean Paul wrote:
> On Tue, Sep 22, 2020 at 11:36 AM Lyude Paul <lyude@redhat.com> wrote:
> > On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
> > > On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
> > > > So if I understand this correctly, it sounds like that some Pixelbooks
> > > > boot up
> > > > with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without
> > > > the
> > > > panel actually having DPCD backlight controls enabled?
> > > 
> > > It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
> > > backlight.enabled = false. By changing backlight.level = max,
> > > backlight.enabled is now set to true. This results in losing backlight
> > > control on boot (since the enable routine is no longer invoked).
> > > 
> > Ahhh ok, I'm fine with that - review still stands :)
> 
> Pinging intel maintainers, could someone please apply this?

oops, sorry about that. I can go ahead and push this
> 
> 
> Sean
> 
> > > Sean
> > > 
> > > > If I'm understanding that correctly, then this patch looks good to me:
> > > > 
> > > > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > > > 
> > > > On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > > > > From: Sean Paul <seanpaul@chromium.org>
> > > > > 
> > > > > In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > > DPCD control mode"), we fixed the brightness level when DPCD control
> > > > > was
> > > > > not active to max brightness. This is as good as we can guess since
> > > > > most
> > > > > backlights go on full when uncontrolled.
> > > > > 
> > > > > However in doing so we changed the semantics of the initial
> > > > > 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> > > > > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> > > > > boot such that enabled would be false. This causes the device to be
> > > > > enabled when the brightness is set. Without this, brightness control
> > > > > doesn't work. So by changing brightness to max, we also flipped
> > > > > enabled
> > > > > to be true on boot.
> > > > > 
> > > > > To fix this, make enabled a function of brightness and backlight
> > > > > control
> > > > > mechanism.
> > > > > 
> > > > > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > > DPCD
> > > > > control mode")
> > > > > Cc: Lyude Paul <lyude@redhat.com>
> > > > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > > > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > > > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > > > Cc: Kevin Chowski <chowski@chromium.org>>
> > > > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > > > ---
> > > > >  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++----
> > > > > ---
> > > > >  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct
> > > > > intel_dp
> > > > > *intel_dp, bool enable)
> > > > >       }
> > > > >  }
> > > > > 
> > > > > -/*
> > > > > - * Read the current backlight value from DPCD register(s) based
> > > > > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > - */
> > > > > -static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > *connector)
> > > > > +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> > > > > *connector)
> > > > >  {
> > > > >       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > >       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > -     u8 read_val[2] = { 0x0 };
> > > > >       u8 mode_reg;
> > > > > -     u16 level = 0;
> > > > > 
> > > > >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > >                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > > > > intel_connector *connector)
> > > > >               drm_dbg_kms(&i915->drm,
> > > > >                           "Failed to read the DPCD register 0x%x\n",
> > > > >                           DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > > > > -             return 0;
> > > > > +             return false;
> > > > >       }
> > > > > 
> > > > > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > > > > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * Read the current backlight value from DPCD register(s) based
> > > > > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > + */
> > > > > +static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > *connector)
> > > > > +{
> > > > > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > +     u8 read_val[2] = { 0x0 };
> > > > > +     u16 level = 0;
> > > > > +
> > > > >       /*
> > > > >        * If we're not in DPCD control mode yet, the programmed
> > > > > brightness
> > > > >        * value is meaningless and we should assume max brightness
> > > > >        */
> > > > > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > > > > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > > > > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> > > > >               return connector->panel.backlight.max;
> > > > > 
> > > > >       if (drm_dp_dpcd_read(&intel_dp->aux,
> > > > > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > > > > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > > > > intel_connector *connector,
> > > > > 
> > > > >       panel->backlight.min = 0;
> > > > >       panel->backlight.level = intel_dp_aux_get_backlight(connector);
> > > > > -     panel->backlight.enabled = panel->backlight.level != 0;
> > > > > +     panel->backlight.enabled =
> > > > > intel_dp_aux_backlight_dpcd_mode(connector)
> > > > > &&
> > > > > +                                panel->backlight.level != 0;
> > > > > 
> > > > >       return 0;
> > > > >  }
> > > > --
> > > > Cheers,
> > > >         Lyude Paul (she/her)
> > > >         Software Engineer at Red Hat
> > > > 
> > --
> > Cheers,
> >         Lyude Paul (she/her)
> >         Software Engineer at Red Hat
> >
Lyude Paul Oct. 12, 2020, 9:47 p.m. UTC | #6
Just pushed this, but it's not in drm-tip because it would seem that rebuilding
drm-tip has failed, and the conflict doesn't appear to be from any of the
patches I pushed so I'm getting the feeling from the DRM maintainer docs I
should probably let one of the drm-misc-folks handle the conflict.

On Mon, 2020-10-12 at 13:50 -0400, Sean Paul wrote:
> On Tue, Sep 22, 2020 at 11:36 AM Lyude Paul <lyude@redhat.com> wrote:
> > On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
> > > On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
> > > > So if I understand this correctly, it sounds like that some Pixelbooks
> > > > boot up
> > > > with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without
> > > > the
> > > > panel actually having DPCD backlight controls enabled?
> > > 
> > > It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
> > > backlight.enabled = false. By changing backlight.level = max,
> > > backlight.enabled is now set to true. This results in losing backlight
> > > control on boot (since the enable routine is no longer invoked).
> > > 
> > Ahhh ok, I'm fine with that - review still stands :)
> 
> Pinging intel maintainers, could someone please apply this?
> 
> 
> Sean
> 
> > > Sean
> > > 
> > > > If I'm understanding that correctly, then this patch looks good to me:
> > > > 
> > > > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > > > 
> > > > On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > > > > From: Sean Paul <seanpaul@chromium.org>
> > > > > 
> > > > > In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > > DPCD control mode"), we fixed the brightness level when DPCD control
> > > > > was
> > > > > not active to max brightness. This is as good as we can guess since
> > > > > most
> > > > > backlights go on full when uncontrolled.
> > > > > 
> > > > > However in doing so we changed the semantics of the initial
> > > > > 'backlight.enabled' value. At least on Pixelbooks, they  were relying
> > > > > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
> > > > > boot such that enabled would be false. This causes the device to be
> > > > > enabled when the brightness is set. Without this, brightness control
> > > > > doesn't work. So by changing brightness to max, we also flipped
> > > > > enabled
> > > > > to be true on boot.
> > > > > 
> > > > > To fix this, make enabled a function of brightness and backlight
> > > > > control
> > > > > mechanism.
> > > > > 
> > > > > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > > DPCD
> > > > > control mode")
> > > > > Cc: Lyude Paul <lyude@redhat.com>
> > > > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > > > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > > > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > > > Cc: Kevin Chowski <chowski@chromium.org>>
> > > > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > > > ---
> > > > >  .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++----
> > > > > ---
> > > > >  1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct
> > > > > intel_dp
> > > > > *intel_dp, bool enable)
> > > > >       }
> > > > >  }
> > > > > 
> > > > > -/*
> > > > > - * Read the current backlight value from DPCD register(s) based
> > > > > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > - */
> > > > > -static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > *connector)
> > > > > +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
> > > > > *connector)
> > > > >  {
> > > > >       struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > >       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > -     u8 read_val[2] = { 0x0 };
> > > > >       u8 mode_reg;
> > > > > -     u16 level = 0;
> > > > > 
> > > > >       if (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > >                             DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > > > > intel_connector *connector)
> > > > >               drm_dbg_kms(&i915->drm,
> > > > >                           "Failed to read the DPCD register 0x%x\n",
> > > > >                           DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > > > > -             return 0;
> > > > > +             return false;
> > > > >       }
> > > > > 
> > > > > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > > > > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * Read the current backlight value from DPCD register(s) based
> > > > > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > + */
> > > > > +static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > *connector)
> > > > > +{
> > > > > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > +     u8 read_val[2] = { 0x0 };
> > > > > +     u16 level = 0;
> > > > > +
> > > > >       /*
> > > > >        * If we're not in DPCD control mode yet, the programmed
> > > > > brightness
> > > > >        * value is meaningless and we should assume max brightness
> > > > >        */
> > > > > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > > > > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > > > > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> > > > >               return connector->panel.backlight.max;
> > > > > 
> > > > >       if (drm_dp_dpcd_read(&intel_dp->aux,
> > > > > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > > > > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > > > > intel_connector *connector,
> > > > > 
> > > > >       panel->backlight.min = 0;
> > > > >       panel->backlight.level = intel_dp_aux_get_backlight(connector);
> > > > > -     panel->backlight.enabled = panel->backlight.level != 0;
> > > > > +     panel->backlight.enabled =
> > > > > intel_dp_aux_backlight_dpcd_mode(connector)
> > > > > &&
> > > > > +                                panel->backlight.level != 0;
> > > > > 
> > > > >       return 0;
> > > > >  }
> > > > --
> > > > Cheers,
> > > >         Lyude Paul (she/her)
> > > >         Software Engineer at Red Hat
> > > > 
> > --
> > Cheers,
> >         Lyude Paul (she/her)
> >         Software Engineer at Red Hat
> >
Rodrigo Vivi Oct. 12, 2020, 10:02 p.m. UTC | #7
> On Oct 12, 2020, at 2:47 PM, Lyude Paul <lyude@redhat.com> wrote:
> 
> Just pushed this, but it's not in drm-tip because it would seem that rebuilding
> drm-tip has failed, and the conflict doesn't appear to be from any of the
> patches I pushed so I'm getting the feeling from the DRM maintainer docs I
> should probably let one of the drm-misc-folks handle the conflict.

conflicts solved. feel free to push now.

For the drm-misc I simply went with the drm-misc-next solution and for the drm-intel
I went with the drm-intel-next-queued one.

> 
> On Mon, 2020-10-12 at 13:50 -0400, Sean Paul wrote:
>> On Tue, Sep 22, 2020 at 11:36 AM Lyude Paul <lyude@redhat.com> wrote:
>>> On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
>>>> On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
>>>>> So if I understand this correctly, it sounds like that some Pixelbooks
>>>>> boot up
>>>>> with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value, without
>>>>> the
>>>>> panel actually having DPCD backlight controls enabled?
>>>> 
>>>> It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
>>>> backlight.enabled = false. By changing backlight.level = max,
>>>> backlight.enabled is now set to true. This results in losing backlight
>>>> control on boot (since the enable routine is no longer invoked).
>>>> 
>>> Ahhh ok, I'm fine with that - review still stands :)
>> 
>> Pinging intel maintainers, could someone please apply this?
>> 
>> 
>> Sean
>> 
>>>> Sean
>>>> 
>>>>> If I'm understanding that correctly, then this patch looks good to me:
>>>>> 
>>>>> Reviewed-by: Lyude Paul <lyude@redhat.com>
>>>>> 
>>>>> On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
>>>>>> From: Sean Paul <seanpaul@chromium.org>
>>>>>> 
>>>>>> In commit 79946723092b ("drm/i915: Assume 100% brightness when not in
>>>>>> DPCD control mode"), we fixed the brightness level when DPCD control
>>>>>> was
>>>>>> not active to max brightness. This is as good as we can guess since
>>>>>> most
>>>>>> backlights go on full when uncontrolled.
>>>>>> 
>>>>>> However in doing so we changed the semantics of the initial
>>>>>> 'backlight.enabled' value. At least on Pixelbooks, they  were relying
>>>>>> on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0 on
>>>>>> boot such that enabled would be false. This causes the device to be
>>>>>> enabled when the brightness is set. Without this, brightness control
>>>>>> doesn't work. So by changing brightness to max, we also flipped
>>>>>> enabled
>>>>>> to be true on boot.
>>>>>> 
>>>>>> To fix this, make enabled a function of brightness and backlight
>>>>>> control
>>>>>> mechanism.
>>>>>> 
>>>>>> Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in
>>>>>> DPCD
>>>>>> control mode")
>>>>>> Cc: Lyude Paul <lyude@redhat.com>
>>>>>> Cc: Jani Nikula <jani.nikula@intel.com>
>>>>>> Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
>>>>>> Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
>>>>>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>>>>> Cc: Kevin Chowski <chowski@chromium.org>>
>>>>>> Signed-off-by: Sean Paul <seanpaul@chromium.org>
>>>>>> ---
>>>>>> .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++----
>>>>>> ---
>>>>>> 1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
>>>>>> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>>>>>> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>>>>>> @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct
>>>>>> intel_dp
>>>>>> *intel_dp, bool enable)
>>>>>>      }
>>>>>> }
>>>>>> 
>>>>>> -/*
>>>>>> - * Read the current backlight value from DPCD register(s) based
>>>>>> - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
>>>>>> - */
>>>>>> -static u32 intel_dp_aux_get_backlight(struct intel_connector
>>>>>> *connector)
>>>>>> +static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector
>>>>>> *connector)
>>>>>> {
>>>>>>      struct intel_dp *intel_dp = intel_attached_dp(connector);
>>>>>>      struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>>>>>> -     u8 read_val[2] = { 0x0 };
>>>>>>      u8 mode_reg;
>>>>>> -     u16 level = 0;
>>>>>> 
>>>>>>      if (drm_dp_dpcd_readb(&intel_dp->aux,
>>>>>>                            DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
>>>>>> @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
>>>>>> intel_connector *connector)
>>>>>>              drm_dbg_kms(&i915->drm,
>>>>>>                          "Failed to read the DPCD register 0x%x\n",
>>>>>>                          DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
>>>>>> -             return 0;
>>>>>> +             return false;
>>>>>>      }
>>>>>> 
>>>>>> +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
>>>>>> +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
>>>>>> +}
>>>>>> +
>>>>>> +/*
>>>>>> + * Read the current backlight value from DPCD register(s) based
>>>>>> + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
>>>>>> + */
>>>>>> +static u32 intel_dp_aux_get_backlight(struct intel_connector
>>>>>> *connector)
>>>>>> +{
>>>>>> +     struct intel_dp *intel_dp = intel_attached_dp(connector);
>>>>>> +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>>>>>> +     u8 read_val[2] = { 0x0 };
>>>>>> +     u16 level = 0;
>>>>>> +
>>>>>>      /*
>>>>>>       * If we're not in DPCD control mode yet, the programmed
>>>>>> brightness
>>>>>>       * value is meaningless and we should assume max brightness
>>>>>>       */
>>>>>> -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
>>>>>> -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
>>>>>> +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
>>>>>>              return connector->panel.backlight.max;
>>>>>> 
>>>>>>      if (drm_dp_dpcd_read(&intel_dp->aux,
>>>>>> DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
>>>>>> @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
>>>>>> intel_connector *connector,
>>>>>> 
>>>>>>      panel->backlight.min = 0;
>>>>>>      panel->backlight.level = intel_dp_aux_get_backlight(connector);
>>>>>> -     panel->backlight.enabled = panel->backlight.level != 0;
>>>>>> +     panel->backlight.enabled =
>>>>>> intel_dp_aux_backlight_dpcd_mode(connector)
>>>>>> &&
>>>>>> +                                panel->backlight.level != 0;
>>>>>> 
>>>>>>      return 0;
>>>>>> }
>>>>> --
>>>>> Cheers,
>>>>>        Lyude Paul (she/her)
>>>>>        Software Engineer at Red Hat
>>>>> 
>>> --
>>> Cheers,
>>>        Lyude Paul (she/her)
>>>        Software Engineer at Red Hat
>>> 
> -- 
> Sincerely,
>      Lyude Paul (she/her)
>      Software Engineer at Red Hat
> 
> Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've
> asked me a question, are waiting for a review/merge on a patch, etc. and I
> haven't responded in a while, please feel free to send me another email to check
> on my status. I don't bite!
>
Lyude Paul Oct. 12, 2020, 10:03 p.m. UTC | #8
On Mon, 2020-10-12 at 22:02 +0000, Vivi, Rodrigo wrote:
> > On Oct 12, 2020, at 2:47 PM, Lyude Paul <lyude@redhat.com> wrote:
> > 
> > Just pushed this, but it's not in drm-tip because it would seem that
> > rebuilding
> > drm-tip has failed, and the conflict doesn't appear to be from any of the
> > patches I pushed so I'm getting the feeling from the DRM maintainer docs I
> > should probably let one of the drm-misc-folks handle the conflict.
> 
> conflicts solved. feel free to push now.

Thank you!
> 
> For the drm-misc I simply went with the drm-misc-next solution and for the
> drm-intel
> I went with the drm-intel-next-queued one.
> 
> > On Mon, 2020-10-12 at 13:50 -0400, Sean Paul wrote:
> > > On Tue, Sep 22, 2020 at 11:36 AM Lyude Paul <lyude@redhat.com> wrote:
> > > > On Tue, 2020-09-22 at 09:39 -0400, Sean Paul wrote:
> > > > > On Mon, Sep 21, 2020 at 6:35 PM Lyude Paul <lyude@redhat.com> wrote:
> > > > > > So if I understand this correctly, it sounds like that some
> > > > > > Pixelbooks
> > > > > > boot up
> > > > > > with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB set to a non-zero value,
> > > > > > without
> > > > > > the
> > > > > > panel actually having DPCD backlight controls enabled?
> > > > > 
> > > > > It boots with DP_EDP_BACKLIGHT_BRIGHTNESS_MSB == 0, which used to set
> > > > > backlight.enabled = false. By changing backlight.level = max,
> > > > > backlight.enabled is now set to true. This results in losing backlight
> > > > > control on boot (since the enable routine is no longer invoked).
> > > > > 
> > > > Ahhh ok, I'm fine with that - review still stands :)
> > > 
> > > Pinging intel maintainers, could someone please apply this?
> > > 
> > > 
> > > Sean
> > > 
> > > > > Sean
> > > > > 
> > > > > > If I'm understanding that correctly, then this patch looks good to
> > > > > > me:
> > > > > > 
> > > > > > Reviewed-by: Lyude Paul <lyude@redhat.com>
> > > > > > 
> > > > > > On Thu, 2020-09-17 at 20:28 -0400, Sean Paul wrote:
> > > > > > > From: Sean Paul <seanpaul@chromium.org>
> > > > > > > 
> > > > > > > In commit 79946723092b ("drm/i915: Assume 100% brightness when not
> > > > > > > in
> > > > > > > DPCD control mode"), we fixed the brightness level when DPCD
> > > > > > > control
> > > > > > > was
> > > > > > > not active to max brightness. This is as good as we can guess
> > > > > > > since
> > > > > > > most
> > > > > > > backlights go on full when uncontrolled.
> > > > > > > 
> > > > > > > However in doing so we changed the semantics of the initial
> > > > > > > 'backlight.enabled' value. At least on Pixelbooks, they  were
> > > > > > > relying
> > > > > > > on the brightness level in DP_EDP_BACKLIGHT_BRIGHTNESS_MSB to be 0
> > > > > > > on
> > > > > > > boot such that enabled would be false. This causes the device to
> > > > > > > be
> > > > > > > enabled when the brightness is set. Without this, brightness
> > > > > > > control
> > > > > > > doesn't work. So by changing brightness to max, we also flipped
> > > > > > > enabled
> > > > > > > to be true on boot.
> > > > > > > 
> > > > > > > To fix this, make enabled a function of brightness and backlight
> > > > > > > control
> > > > > > > mechanism.
> > > > > > > 
> > > > > > > Fixes: 79946723092b ("drm/i915: Assume 100% brightness when not in
> > > > > > > DPCD
> > > > > > > control mode")
> > > > > > > Cc: Lyude Paul <lyude@redhat.com>
> > > > > > > Cc: Jani Nikula <jani.nikula@intel.com>
> > > > > > > Cc: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> > > > > > > Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
> > > > > > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > > > > > Cc: Kevin Chowski <chowski@chromium.org>>
> > > > > > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > > > > > ---
> > > > > > > .../drm/i915/display/intel_dp_aux_backlight.c | 31 ++++++++++++---
> > > > > > > -
> > > > > > > ---
> > > > > > > 1 file changed, 20 insertions(+), 11 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 acbd7eb66cbe..036f504ac7db 100644
> > > > > > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > > > > > > @@ -52,17 +52,11 @@ static void set_aux_backlight_enable(struct
> > > > > > > intel_dp
> > > > > > > *intel_dp, bool enable)
> > > > > > >      }
> > > > > > > }
> > > > > > > 
> > > > > > > -/*
> > > > > > > - * Read the current backlight value from DPCD register(s) based
> > > > > > > - * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > > > - */
> > > > > > > -static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > > > *connector)
> > > > > > > +static bool intel_dp_aux_backlight_dpcd_mode(struct
> > > > > > > intel_connector
> > > > > > > *connector)
> > > > > > > {
> > > > > > >      struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > > > >      struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > > > -     u8 read_val[2] = { 0x0 };
> > > > > > >      u8 mode_reg;
> > > > > > > -     u16 level = 0;
> > > > > > > 
> > > > > > >      if (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > > > >                            DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > > > > @@ -70,15 +64,29 @@ static u32 intel_dp_aux_get_backlight(struct
> > > > > > > intel_connector *connector)
> > > > > > >              drm_dbg_kms(&i915->drm,
> > > > > > >                          "Failed to read the DPCD register
> > > > > > > 0x%x\n",
> > > > > > >                          DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
> > > > > > > -             return 0;
> > > > > > > +             return false;
> > > > > > >      }
> > > > > > > 
> > > > > > > +     return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
> > > > > > > +            DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> > > > > > > +}
> > > > > > > +
> > > > > > > +/*
> > > > > > > + * Read the current backlight value from DPCD register(s) based
> > > > > > > + * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
> > > > > > > + */
> > > > > > > +static u32 intel_dp_aux_get_backlight(struct intel_connector
> > > > > > > *connector)
> > > > > > > +{
> > > > > > > +     struct intel_dp *intel_dp = intel_attached_dp(connector);
> > > > > > > +     struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > > > > > +     u8 read_val[2] = { 0x0 };
> > > > > > > +     u16 level = 0;
> > > > > > > +
> > > > > > >      /*
> > > > > > >       * If we're not in DPCD control mode yet, the programmed
> > > > > > > brightness
> > > > > > >       * value is meaningless and we should assume max brightness
> > > > > > >       */
> > > > > > > -     if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
> > > > > > > -         DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
> > > > > > > +     if (!intel_dp_aux_backlight_dpcd_mode(connector))
> > > > > > >              return connector->panel.backlight.max;
> > > > > > > 
> > > > > > >      if (drm_dp_dpcd_read(&intel_dp->aux,
> > > > > > > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
> > > > > > > @@ -319,7 +327,8 @@ static int intel_dp_aux_setup_backlight(struct
> > > > > > > intel_connector *connector,
> > > > > > > 
> > > > > > >      panel->backlight.min = 0;
> > > > > > >      panel->backlight.level =
> > > > > > > intel_dp_aux_get_backlight(connector);
> > > > > > > -     panel->backlight.enabled = panel->backlight.level != 0;
> > > > > > > +     panel->backlight.enabled =
> > > > > > > intel_dp_aux_backlight_dpcd_mode(connector)
> > > > > > > &&
> > > > > > > +                                panel->backlight.level != 0;
> > > > > > > 
> > > > > > >      return 0;
> > > > > > > }
> > > > > > --
> > > > > > Cheers,
> > > > > >        Lyude Paul (she/her)
> > > > > >        Software Engineer at Red Hat
> > > > > > 
> > > > --
> > > > Cheers,
> > > >        Lyude Paul (she/her)
> > > >        Software Engineer at Red Hat
> > > > 
> > -- 
> > Sincerely,
> >      Lyude Paul (she/her)
> >      Software Engineer at Red Hat
> > 
> > Note: I deal with a lot of emails and have a lot of bugs on my plate. If
> > you've
> > asked me a question, are waiting for a review/merge on a patch, etc. and I
> > haven't responded in a while, please feel free to send me another email to
> > check
> > on my status. I don't bite!
> >
diff mbox series

Patch

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 acbd7eb66cbe..036f504ac7db 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -52,17 +52,11 @@  static void set_aux_backlight_enable(struct intel_dp *intel_dp, bool enable)
 	}
 }
 
-/*
- * Read the current backlight value from DPCD register(s) based
- * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
- */
-static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
+static bool intel_dp_aux_backlight_dpcd_mode(struct intel_connector *connector)
 {
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
-	u8 read_val[2] = { 0x0 };
 	u8 mode_reg;
-	u16 level = 0;
 
 	if (drm_dp_dpcd_readb(&intel_dp->aux,
 			      DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
@@ -70,15 +64,29 @@  static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
 		drm_dbg_kms(&i915->drm,
 			    "Failed to read the DPCD register 0x%x\n",
 			    DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
-		return 0;
+		return false;
 	}
 
+	return (mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
+	       DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
+}
+
+/*
+ * Read the current backlight value from DPCD register(s) based
+ * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
+ */
+static u32 intel_dp_aux_get_backlight(struct intel_connector *connector)
+{
+	struct intel_dp *intel_dp = intel_attached_dp(connector);
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 read_val[2] = { 0x0 };
+	u16 level = 0;
+
 	/*
 	 * If we're not in DPCD control mode yet, the programmed brightness
 	 * value is meaningless and we should assume max brightness
 	 */
-	if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) !=
-	    DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD)
+	if (!intel_dp_aux_backlight_dpcd_mode(connector))
 		return connector->panel.backlight.max;
 
 	if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
@@ -319,7 +327,8 @@  static int intel_dp_aux_setup_backlight(struct intel_connector *connector,
 
 	panel->backlight.min = 0;
 	panel->backlight.level = intel_dp_aux_get_backlight(connector);
-	panel->backlight.enabled = panel->backlight.level != 0;
+	panel->backlight.enabled = intel_dp_aux_backlight_dpcd_mode(connector) &&
+				   panel->backlight.level != 0;
 
 	return 0;
 }