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>,
Perry Yuan <pyuan@redhat.com>
Subject: Re: [Intel-gfx] [PATCH v3 4/5] drm/i915: Don't use VBT for detecting DPCD backlight controls
Date: Fri, 17 Jan 2020 13:36:12 +0200 [thread overview]
Message-ID: <87zhemgvrn.fsf@intel.com> (raw)
In-Reply-To: <20200116211623.53799-5-lyude@redhat.com>
On Thu, 16 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, but only to make sure that we don't enable DPCD backlight
> controls on a panel that uses something other then the standard VESA
> interfaces over AUX. Since panels using such non-standard interfaces
> should probably have support added to i915, we'll print a warning when
> seeing this in the VBT. We can remove this warning later if we end up
> adding support for any custom 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>
> ---
> .../drm/i915/display/intel_dp_aux_backlight.c | 16 ++++++++++------
> 1 file changed, 10 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 77a759361c5c..3002b600635f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -330,13 +330,17 @@ 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);
>
> - if (i915_modparams.enable_dpcd_backlight == 0 ||
> - (i915_modparams.enable_dpcd_backlight == -1 &&
> - dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
> - return -ENODEV;
> -
> - if (!intel_dp_aux_display_control_capable(intel_connector))
> + if (i915_modparams.enable_dpcd_backlight == 0)
> return -ENODEV;
> + if (i915_modparams.enable_dpcd_backlight == -1) {
> + if (dev_priv->vbt.backlight.type
> + == INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE) {
> + DRM_WARN("VBT says panel uses custom panel driver interface, not using DPCD backlight controls\n");
> + return -ENODEV;
> + }
> + if (!intel_dp_aux_display_control_capable(intel_connector))
> + return -ENODEV;
Functionally, I'm fine with trying this. But perhaps we should check aux
and early return first, and then check what vbt says, to reduce the
dmesg noise.
I'll probably want to see a debug message if we're enabling aux
backlight even if dev_priv->vbt.backlight.type !=
INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE. It's the kind of debug trace
you'll really want to get first.
BR,
Jani.
> + }
>
> panel->backlight.setup = intel_dp_aux_setup_backlight;
> panel->backlight.enable = intel_dp_aux_enable_backlight;
--
Jani Nikula, Intel Open Source Graphics Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2020-01-17 11:36 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 21:16 [Intel-gfx] [PATCH v3 0/5] drm/i915: eDP DPCD aux backlight fixes Lyude Paul
2020-01-16 21:16 ` [Intel-gfx] [PATCH v3 1/5] drm/i915: Fix eDP DPCD aux max backlight calculations Lyude Paul
2020-01-16 21:16 ` [Intel-gfx] [PATCH v3 2/5] drm/i915: Assume 100% brightness when not in DPCD control mode Lyude Paul
2020-01-16 21:16 ` [Intel-gfx] [PATCH v3 3/5] drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight() Lyude Paul
2020-01-16 21:16 ` [Intel-gfx] [PATCH v3 4/5] drm/i915: Don't use VBT for detecting DPCD backlight controls Lyude Paul
2020-01-17 11:36 ` Jani Nikula [this message]
2020-01-17 11:47 ` Jani Nikula
2020-01-17 20:24 ` Lyude Paul
2020-01-17 23:21 ` [Intel-gfx] [PATCH v4] " Lyude Paul
2020-01-22 9:17 ` Jani Nikula
2020-01-16 21:16 ` [Intel-gfx] [PATCH v3 5/5] drm/i915: Auto detect DPCD backlight support by default Lyude Paul
2020-01-16 23:26 ` [Intel-gfx] ✓ Fi.CI.BAT: success for drm/i915: eDP DPCD aux backlight fixes (rev6) Patchwork
2020-01-16 23:26 ` [Intel-gfx] ✗ Fi.CI.BUILD: warning " Patchwork
2020-01-18 3:23 ` [Intel-gfx] ✓ Fi.CI.BAT: success for drm/i915: eDP DPCD aux backlight fixes (rev7) Patchwork
2020-01-18 3:23 ` [Intel-gfx] ✗ Fi.CI.BUILD: warning " Patchwork
2020-01-20 5:16 ` [Intel-gfx] ✓ Fi.CI.IGT: success for drm/i915: eDP DPCD aux backlight fixes (rev6) Patchwork
2020-01-20 19:55 ` [Intel-gfx] ✓ Fi.CI.IGT: success for drm/i915: eDP DPCD aux backlight fixes (rev7) Patchwork
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87zhemgvrn.fsf@intel.com \
--to=jani.nikula@intel.com \
--cc=acelan.kao@canonical.com \
--cc=airlied@linux.ie \
--cc=dri-devel@lists.freedesktop.org \
--cc=intel-gfx@lists.freedesktop.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lyude@redhat.com \
--cc=pyuan@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).