From: Jani Nikula <jani.nikula@intel.com>
To: Lyude Paul <lyude@redhat.com>, intel-gfx@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
AceLan Kao <acelan.kao@canonical.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Perry Yuan <pyuan@redhat.com>,
Lee Shawn C <shawn.c.lee@intel.com>
Subject: Re: [PATCH v4] drm/i915: Don't use VBT for detecting DPCD backlight controls
Date: Wed, 22 Jan 2020 11:17:32 +0200 [thread overview]
Message-ID: <87lfpzj1eb.fsf@intel.com> (raw)
In-Reply-To: <20200117232155.135579-1-lyude@redhat.com>
On Fri, 17 Jan 2020, Lyude Paul <lyude@redhat.com> wrote:
> Despite the fact that the VBT appears to have a field for specifying
> that a system is equipped with a panel that supports standard VESA
> backlight controls over the DP AUX channel, so far every system we've
> spotted DPCD backlight control support on doesn't actually set this
> field correctly and all have it set to INTEL_BACKLIGHT_DISPLAY_DDI.
>
> While we don't know the exact reason for this VBT misuse, talking with
> some vendors indicated that there's a good number of laptop panels out
> there that supposedly support both PWM backlight controls and DPCD
> backlight controls as a workaround until Intel supports DPCD backlight
> controls across platforms universally. This being said, the X1 Extreme
> 2nd Gen that I have here (note that Lenovo is not the hardware vendor
> that informed us of this) PWM backlight controls are advertised, but
> only DPCD controls actually function. I'm going to make an educated
> guess here and say that on systems like this one, it's likely that PWM
> backlight controls might have been intended to work but were never
> really tested by QA.
>
> Since we really need backlights to work without any extra module
> parameters, let's take the risk here and rely on the standard DPCD caps
> to tell us whether AUX backlight controls are supported or not. We still
> check the VBT, just so we can print a debugging message on systems that
> advertise DPCD backlight support on the panel but not in the VBT.
>
> Changes since v3:
> * Print a debugging message if we enable DPCD backlight control on a
> device which doesn't report DPCD backlight controls in it's VBT,
> instead of warning on custom panel backlight interfaces.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112376
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Perry Yuan <pyuan@redhat.com>
> Cc: AceLan Kao <acelan.kao@canonical.com>
Thanks for the patch, pushed to dinq, fingers crossed! ;)
BR,
Jani.
> ---
> drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 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 77a759361c5c..0f8edc775375 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -328,15 +328,16 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector)
> int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
> {
> struct intel_panel *panel = &intel_connector->panel;
> - struct drm_i915_private *dev_priv = to_i915(intel_connector->base.dev);
> + enum intel_backlight_type type =
> + to_i915(intel_connector->base.dev)->vbt.backlight.type;
>
> if (i915_modparams.enable_dpcd_backlight == 0 ||
> (i915_modparams.enable_dpcd_backlight == -1 &&
> - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
> + !intel_dp_aux_display_control_capable(intel_connector)))
> return -ENODEV;
>
> - if (!intel_dp_aux_display_control_capable(intel_connector))
> - return -ENODEV;
> + if (type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)
> + DRM_DEBUG_DRIVER("Ignoring VBT backlight type\n");
>
> panel->backlight.setup = intel_dp_aux_setup_backlight;
> panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Jani Nikula, Intel Open Source Graphics Center
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next prev parent reply other threads:[~2020-01-22 9:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 21:16 [PATCH v3 0/5] drm/i915: eDP DPCD aux backlight fixes Lyude Paul
2020-01-16 21:16 ` [PATCH v3 1/5] drm/i915: Fix eDP DPCD aux max backlight calculations Lyude Paul
2020-01-16 21:16 ` [PATCH v3 2/5] drm/i915: Assume 100% brightness when not in DPCD control mode Lyude Paul
2020-01-16 21:16 ` [PATCH v3 3/5] drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight() Lyude Paul
2020-01-16 21:16 ` [PATCH v3 4/5] drm/i915: Don't use VBT for detecting DPCD backlight controls Lyude Paul
2020-01-17 11:36 ` Jani Nikula
2020-01-17 11:47 ` Jani Nikula
2020-01-17 20:24 ` Lyude Paul
2020-01-17 23:21 ` [PATCH v4] " Lyude Paul
2020-01-22 9:17 ` Jani Nikula [this message]
2020-01-16 21:16 ` [PATCH v3 5/5] drm/i915: Auto detect DPCD backlight support by default Lyude Paul
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