linux-kernel - Re: [PATCH v2 4/4] drm/dp: fallback to maximum when PWM bit count is zero

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Message-ID: <Z+UGqItLubQ9kwF+@linaro.org>
Date: Thu, 27 Mar 2025 10:04:56 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Christopher Obbard <christopher.obbard@...aro.org>
Cc: Douglas Anderson <dianders@...omium.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, Johan Hovold <johan@...nel.org>,
	Rui Miguel Silva <rui.silva@...aro.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 4/4] drm/dp: fallback to maximum when PWM bit count is
 zero

On 25-03-25 19:21:29, Christopher Obbard wrote:
> Some eDP devices report DP_EDP_PWMGEN_BIT_COUNT as 0, but still provide
> valid non-zero MIN and MAX values. This patch reworks the logic to
> fallback to the max value in such cases, ensuring correct backlight PWM
> configuration even when the bit count value is not explicitly set.
> 
> This improves compatibility with eDP panels (e.g. Samsung ATNA40YK20
> used on the Lenovo T14s Gen6 Snapdragon with OLED panel) which reports
> DP_EDP_PWMGEN_BIT_COUNT as 0 but still provides valid non-zero MIN/MAX
> values.
> 

Nit-pick: AFAICT, there is no relationship between this patch and the
rest. So it should've probably not be part of this patchset.