From: Sean Paul <seanpaul@chromium.org>
To: Alexandru M Stan <amstan@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
dri-devel@lists.freedesktop.org, dianders@chromium.org,
zain wang <wzz@rock-chips.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Sylwester Nawrocki <s.nawrocki@samsung.com>,
hoegsberg@chromium.org,
Marek Szyprowski <m.szyprowski@samsung.com>,
briannorris@chromium.org, linux-rockchip@lists.infradead.org,
devicetree@vger.kernel.org,
Jeffy Chen <jeffy.chen@rock-chips.com>,
Rob Herring <robh+dt@kernel.org>,
marcheu@chromium.org,
Thierry Escande <thierry.escande@collabora.com>,
linux-kernel@vger.kernel.org,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
Yakir Yang <kuankuan.y@gmail.com>
Subject: Re: [PATCH 0/2] Add backlight-pwm-passthru in analogix DP driver
Date: Fri, 16 Mar 2018 12:50:21 -0400 [thread overview]
Message-ID: <20180316165021.GG223881@art_vandelay> (raw)
In-Reply-To: <20180316025659.217423-1-amstan@chromium.org>
On Thu, Mar 15, 2018 at 07:56:57PM -0700, Alexandru M Stan wrote:
> I noticed that the backlight on the ASUS Chromebook Flip C101 (bob) is
> flickering.
>
> We're sending it a high frequency pwm signal, but the EDP panel decided to
> "parse" the signal, read the duty cycle, then make its own signal that
> it sends to the LEDs.
>
> So even though we send a nice high refresh rate at 1200Hz, the panel backlight
> flickers at 200Hz (which is not even divisible by the 60Hz refresh rate).
>
> The fix for that is to enable the EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU bit from
> the DPCD EDP registers. This makes the panel actually follow the signal
> we're giving it.
>
> This series includes the optional dt binding to enable this fix
> (backlight-pwm-passthru) and the corresponding code in the analogix
> drm/bridge driver.
>
Thanks for sending these patches!
With Archit and Daniel's comments addressed, feel free to add my
Reviewed-by: Sean Paul <seanpaul@chromium.org>
>
> Alexandru M Stan (2):
> dt-bindings: analogix-dp: Add backlight-pwm-passthru
> drm/bridge: analogix: Enable EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU
>
> .../bindings/display/bridge/analogix_dp.txt | 4 ++
> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 48 ++++++++++++++++++++++
> drivers/gpu/drm/bridge/analogix/analogix_dp_core.h | 1 +
> 3 files changed, 53 insertions(+)
>
> --
> 2.13.5
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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prev parent reply other threads:[~2018-03-16 16:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-16 2:56 [PATCH 0/2] Add backlight-pwm-passthru in analogix DP driver Alexandru M Stan
2018-03-16 2:56 ` [PATCH 1/2] dt-bindings: analogix-dp: Add backlight-pwm-passthru Alexandru M Stan
2018-03-16 9:26 ` Archit Taneja
2018-03-18 12:52 ` Rob Herring
2018-03-20 14:07 ` Laurent Pinchart
2018-03-16 2:56 ` [PATCH 2/2] drm/bridge: analogix: Enable EDP_BACKLIGHT_FREQ_PWM_PIN_PASSTHRU Alexandru M Stan
2018-03-16 8:36 ` Daniel Vetter
2018-03-16 16:50 ` Sean Paul [this message]
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