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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b6d9b536710sm1383533766b.57.2025.10.30.04.27.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Oct 2025 04:27:26 -0700 (PDT) Message-ID: Date: Thu, 30 Oct 2025 12:27:24 +0100 Precedence: bulk X-Mailing-List: linux-kernel@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> <8caa1cec-d881-4e77-8d77-be043f8d13d6@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDMwMDA5MyBTYWx0ZWRfX4P2Nl+piHX4h yK9dnthNoIaFPiHrwVygZBrL0E0B6JOQ+3NFAqa9RKBIyzoKENcWV2HaYELty+UxHSIaktpdjLO fkENxeYCMHAj+hCuIv/mG5idVyb7878Q7MoK69cTXS5bTX9FZ9E9VJ344oVystdCEYvBjRdGNX5 1tEGOgf+P4xC1g+3byffP98WBOjRt8dcqcNQIdCbekKbzNtoyZjAF/nG7CdCI3sAnS5ZJ8GKokd UktRtRuaN7kdDaI3KerPm/QEewVnUbjsuahSC3ZQtGaqP2H/uxJkEQKJAAoG/ZtDtqu5IQ9OP05 f5phqE6lSRypv/3+Wic+TUWE9TqmbXz1Oy9/FogjxeSoyZ92SLPI1AL2byAi3pasAeoE9FRnZaY vCFYq2f+xaI0JAAJEmGXW83uvweIwQ== X-Authority-Analysis: v=2.4 cv=P+Y3RyAu c=1 sm=1 tr=0 ts=69034ba0 cx=c_pps a=WeENfcodrlLV9YRTxbY/uA==:117 a=FpWmc02/iXfjRdCD7H54yg==: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=tbJ83c6aquYa7vyjLWoA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=kacYvNCVWA4VmyqE58fU:22 a=cvBusfyB2V15izCimMoJ:22 X-Proofpoint-ORIG-GUID: zr4YK2qvztVpfQV4vMxAaQq_mE6rPjXO X-Proofpoint-GUID: zr4YK2qvztVpfQV4vMxAaQq_mE6rPjXO 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 clxscore=1015 suspectscore=0 spamscore=0 lowpriorityscore=0 priorityscore=1501 phishscore=0 malwarescore=0 adultscore=0 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2510300093 On 10/30/25 12:07 PM, Yongxing Mou wrote: > > > 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 ? I think so.. perhaps make sure the period is appropriate for the backlight device at the other end since you mentioned it's flickering Konrad