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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b6d85308cb0sm1743866166b.9.2025.10.30.02.41.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Oct 2025 02:41:53 -0700 (PDT) Message-ID: <8caa1cec-d881-4e77-8d77-be043f8d13d6@oss.qualcomm.com> Date: Thu, 30 Oct 2025 10:41:51 +0100 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: dts: qcom: Add backlight support for eDP panel To: Yongxing Mou , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251028-hamoa_dvt_backlight-v1-1-97ecb8d0ad01@oss.qualcomm.com> <0cf2521b-8d05-42f0-aab8-35cd370e599e@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <0cf2521b-8d05-42f0-aab8-35cd370e599e@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDMwMDA3OSBTYWx0ZWRfX1x8ZGGrF3/uY HxzyG9AUTTo7Cc8AEv5FuQBFw09p/YYaF9AleM/7/P/HkK2Glg+CCKZZPom6l4vZqRsD8t7fdKz 2kXyEhcaiu7oxgg3hU2GYCvVawXcBgYXGXEq6jrRQexbLfSncF5k7ScpbyUxn/QSy2j9ADOP75o jsTT3U7ZhYqLozTkMTGroqUjrAV43xCgDqhJTZX7SoBlZoOUsbSifQXZpFIwGUun4cRwHq13SH0 4bMrsJCYwU9P6FdscY4R4FzJvR8/4f5unWGAXarzIEPLGv/1B4h+s8r5uslMWoGtKVsoCznKQkq BnQe+AGiiEpHGdux68WCMCkoaCDeG/lKvOvXG+qo9FNRe3GrWN+UHpnkN8PxWUD2+wIAc5v7EZg yT2gPf9qDAsQSZ19TRFqrKdHydjM5g== X-Authority-Analysis: v=2.4 cv=S8XUAYsP c=1 sm=1 tr=0 ts=690332e4 cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=gZJ2WMP_fuF1vj9OyeAA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 X-Proofpoint-GUID: UjokEOmD9___OmmdJfhuFy8VmXkpinbq X-Proofpoint-ORIG-GUID: UjokEOmD9___OmmdJfhuFy8VmXkpinbq X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-10-30_02,2025-10-29_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 spamscore=0 bulkscore=0 clxscore=1015 phishscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2510300079 On 10/30/25 10:08 AM, Yongxing Mou wrote: > > > On 10/28/2025 5:08 PM, Konrad Dybcio wrote: >> On 10/28/25 8:04 AM, Yongxing Mou wrote: >>> Previously, the eDP panel backlight was enabled via UEFI. Added backlight >>> control node in kernel DTS due to some meta may not enable the backlight. >>> >>> Aligned with other x1e80100-based platforms: the PWM signal is controlled >>> by PMK8550, and the backlight enable signal is handled by PMC8380. >>> >>> Signed-off-by: Yongxing Mou >>> --- >> >> The subject must say "hamoa-iot-evk:" > Thanks and got it , will fix it in next version.>> arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts | 55 ++++++++++++++++++++++++++++++ >>>   1 file changed, 55 insertions(+) >>> >>> diff --git a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts >>> index 36dd6599402b4650b7f8ad2c0cd22212116a25fe..fda1b3a3c7673be74832c27849231cba4bc1f25f 100644 >>> --- a/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts >>> +++ b/arch/arm64/boot/dts/qcom/hamoa-iot-evk.dts >>> @@ -17,6 +17,16 @@ aliases { >>>           serial1 = &uart14; >>>       }; >>>   +    backlight: backlight { >>> +        compatible = "pwm-backlight"; >>> +        pwms = <&pmk8550_pwm 0 5000000>; >> >> Try adjusting the backlight value.. you'll find some funny behavior >> near the max level.. which reminds me I should send some fixes for >> some laptop DTs >> >  I tried sliding the backlight between the maximum and minimum values. It seems that at a certain sliding speed, when approaching the maximum value, there is some brightness flickering. Is this the phenomenon you’re referring to?> [...] "maybe" - for me it was the brightness actually going down beyond ~80% The issue is that the PWM hardware can't really do a period that's == 5000000 ns But it seems like this is no longer an issue since the driver now rounds up to the closest supported value, see last couple commits to drivers/leds/rgb/leds-qcom-lpg.c Konrad