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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-340509e95a3sm2234442a91.19.2025.10.30.04.07.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Oct 2025 04:07:56 -0700 (PDT) Message-ID: Date: Thu, 30 Oct 2025 19:07:50 +0800 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: Konrad Dybcio , 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> <8caa1cec-d881-4e77-8d77-be043f8d13d6@oss.qualcomm.com> Content-Language: en-US From: Yongxing Mou In-Reply-To: <8caa1cec-d881-4e77-8d77-be043f8d13d6@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDMwMDA5MCBTYWx0ZWRfX5wxxP9UO5/qV FgPvxSiHxchuslwqyJOz/G+pL3R1KkLWAlTXOWEDODO2hPqPHk8sH3P6lf6QIVhEsek1lOHLqgO rtBq2w/PJFj+u8DsV8nFbrTHfzP2XjNbdP6zmIBT2xrLz+/77GiVuOXWyBudTzUBaKnxVnIv7Eu hApfBRXwPE18IsWaB8+a5eGHr06Q/ymUu8oaSpEPDtF1QU53N7mGlHnmiSuqnY4xIcEhmhDytKy Ty4umVtICGGfb00MZiDsc8piCexidwtxwfUYZaXuxECmKTPZi3ZsmFA+6axcS/d4TuH6/hwe+TM nkKrtTTGLIkX3Y+unD76cxd33PKTbLajoSqREKOioLU0+uyZIXGKfgsRYQicD6wKG7EGdxvoO65 m9xgS36Znj488z0cltYHKRtYERQcmA== X-Authority-Analysis: v=2.4 cv=KePfcAYD c=1 sm=1 tr=0 ts=6903470e cx=c_pps a=RP+M6JBNLl+fLTcSJhASfg==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=KKAkSRfTAAAA:8 a=EUspDBNiAAAA:8 a=gZJ2WMP_fuF1vj9OyeAA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=iS9zxrgQBfv6-_F4QbHw:22 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-ORIG-GUID: zeXENwDn8FsIho6IjTYRA22zJWMaX1SE X-Proofpoint-GUID: zeXENwDn8FsIho6IjTYRA22zJWMaX1SE 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_03,2025-10-29_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 phishscore=0 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2510300090 On 10/30/2025 5:41 PM, Konrad Dybcio wrote: > 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 Oh,thanks for sharing that. I saw the phenomenon you mentioned. Previously, my baseline had already merged this patch series: https://lore.kernel.org/all/20250305-leds-qcom-lpg-fix-max-pwm-on-hi-res-v4-0-bfe124a53a9f@linaro.org/, so I didn’t observe the ‘brightness actually going down beyond ~80%.’and just very slight flickering. After I reverted patches, it indeed appeared. So here i want to confirm, pwms = <&pmk8550_pwm 0 5000000> can i keep the value 5000000 ?