Date:   Fri, 9 Jul 2021 15:31:44 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Rajeev Nandan <rajeevny@...eaurora.org>,
        linux-fbdev@...r.kernel.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Jani Nikula <jani.nikula@...el.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Sean Paul <seanpaul@...omium.org>,
        Kalyan Thota <kalyan_t@...eaurora.org>,
        Krishna Manikandan <mkrishn@...eaurora.org>,
        Jingoo Han <jingoohan1@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [v8 0/6] drm: Support basic DPCD backlight in panel-simple and
 add a new panel ATNA33XC20

Hi,

On Fri, Jul 9, 2021 at 1:41 PM Ville Syrjälä
<ville.syrjala@...ux.intel.com> wrote:
>
> On Fri, Jul 09, 2021 at 06:54:05AM -0700, Doug Anderson wrote:
> > Hi,
> >
> > On Sat, Jun 26, 2021 at 9:52 AM Rajeev Nandan <rajeevny@...eaurora.org> wrote:
> > >
> > > This series adds the support for the eDP panel that needs the backlight
> > > controlling over the DP AUX channel using DPCD registers of the panel
> > > as per the VESA's standard.
> > >
> > > This series also adds support for the Samsung eDP AMOLED panel that
> > > needs DP AUX to control the backlight, and introduces new delays in the
> > > @panel_desc.delay to support this panel.
> > >
> > > This patch series depends on the following two series:
> > > - Doug's series [1], exposed the DP AUX channel to the panel-simple.
> > > - Lyude's series [2], introduced new drm helper functions for DPCD
> > >   backlight.
> > >
> > > This series is the logical successor to the series [3].
> > >
> > > Changes in v1:
> > > - Created dpcd backlight helper with very basic functionality, added
> > >   backlight registration in the ti-sn65dsi86 bridge driver.
> > >
> > > Changes in v2:
> > > - Created a new DisplayPort aux backlight driver and moved the code from
> > >   drm_dp_aux_backlight.c (v1) to the new driver.
> > >
> > > Changes in v3:
> > > - Fixed module compilation (kernel test bot).
> > >
> > > Changes in v4:
> > > - Added basic DPCD backlight support in panel-simple.
> > > - Added support for a new Samsung panel ATNA33XC20 that needs DPCD
> > >   backlight controlling and has a requirement of delays between enable
> > >   GPIO and regulator.
> > >
> > > Changes in v5:
> > > Addressed review suggestions from Douglas:
> > > - Created a new API drm_panel_dp_aux_backlight() in drm_panel.c
> > > - Moved DP AUX backlight functions from panel-simple.c to drm_panel.c
> > > - panel-simple probe() calls drm_panel_dp_aux_backlight() to create
> > >   backlight when the backlight phandle is not specified in panel DT
> > >   and DP AUX channel is present.
> > > - Added check for drm_edp_backlight_supported() before registering.
> > > - Removed the @uses_dpcd_backlight flag from panel_desc as this
> > >   should be auto-detected.
> > > - Updated comments/descriptions.
> > >
> > > Changes in v6:
> > > - Rebased
> > > - Updated wanrning messages, fixed word wrapping in comments.
> > > - Fixed ordering of memory allocation
> > >
> > > Changes in v7:
> > > - Updated the disable_to_power_off and power_to_enable panel delays
> > > as discovered at <https://crrev.com/c/2966167> (Douglas)
> > >
> > > Changes in v8:
> > > - Now using backlight_is_blank() to get the backlight blank status (Sam Ravnborg)
> > > - Added a new patch #4 to fix the warnings for eDP panel description (Sam Ravnborg)
> > >
> > > [1] https://lore.kernel.org/dri-devel/20210525000159.3384921-1-dianders@chromium.org/
> > > [2] https://lore.kernel.org/dri-devel/20210514181504.565252-1-lyude@redhat.com/
> > > [3] https://lore.kernel.org/dri-devel/1619416756-3533-1-git-send-email-rajeevny@codeaurora.org/
> > >
> > > Rajeev Nandan (6):
> > >   drm/panel: add basic DP AUX backlight support
> > >   drm/panel-simple: Support DP AUX backlight
> > >   drm/panel-simple: Support for delays between GPIO & regulator
> > >   drm/panel-simple: Update validation warnings for eDP panel description
> > >   dt-bindings: display: simple: Add Samsung ATNA33XC20
> > >   drm/panel-simple: Add Samsung ATNA33XC20
> > >
> > >  .../bindings/display/panel/panel-simple.yaml       |   2 +
> > >  drivers/gpu/drm/drm_panel.c                        | 108 +++++++++++++++++++++
> > >  drivers/gpu/drm/panel/panel-simple.c               |  73 +++++++++++++-
> > >  include/drm/drm_panel.h                            |  15 ++-
> > >  4 files changed, 190 insertions(+), 8 deletions(-)
> >
> > Pushed to drm-misc-next.
> >
> > 4bfe6c8f7c23 drm/panel-simple: Add Samsung ATNA33XC20
> > c20dec193584 dt-bindings: display: simple: Add Samsung ATNA33XC20
> > 13aceea56fd5 drm/panel-simple: Update validation warnings for eDP
> > panel description
> > 18a1488bf1e1 drm/panel-simple: Support for delays between GPIO & regulator
> > bfd451403d70 drm/panel-simple: Support DP AUX backlight
> > 10f7b40e4f30 drm/panel: add basic DP AUX backlight support
>
> depmod: ERROR: Cycle detected: drm_kms_helper -> drm -> drm_kms_helper
>
> Looks to be due to drm_edp_backlight_enable().

Ugh. Thanks for the report! I've taken a schwag at a fix here:

https://lore.kernel.org/lkml/20210709152909.1.I23eb4cc5a680341e7b3e791632a635566fa5806a@changeid/

-Doug

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