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Mon, 29 Jun 2026 05:13:03 -0700 (PDT) X-Received: by 2002:a05:6123:5c8:20b0:5bd:9565:2e8a with SMTP id 71dfb90a1353d-5bd95653060mr664826e0c.1.1782735183128; Mon, 29 Jun 2026 05:13:03 -0700 (PDT) Received: from [192.168.120.170] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-697f3ac461csm6870601a12.6.2026.06.29.05.13.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jun 2026 05:13:02 -0700 (PDT) Message-ID: <0d4fa333-df22-42b9-b9c2-ccb43ac4fac3@oss.qualcomm.com> Date: Mon, 29 Jun 2026 14:13:00 +0200 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 v3 0/2] regulator: qcom-rpmh: Add off-on-delay support To: Kamal Wadhwa Cc: Saikiran , broonie@kernel.org, monish.chunara@oss.qualcomm.com, jishnu.prakash@oss.qualcomm.com, nitin.rawat@oss.qualcomm.com, Bjorn Andersson , lgirdwood@gmail.com, andersson@kernel.org, konrad.dybcio@kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, robh@kernel.org, krzk+dt@kernel.org, devicetree@vger.kernel.org References: <20260127190211.14312-1-bjsaikiran@gmail.com> <20260515111647.qg75thdvcbvvjpoi@hu-kamalw-hyd.qualcomm.com> <06a264d0-6a14-4b71-b783-82b771f04411@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: XvFnEKFwBWvACmLpWunog5KU_geWwcPs X-Proofpoint-ORIG-GUID: XvFnEKFwBWvACmLpWunog5KU_geWwcPs X-Authority-Analysis: v=2.4 cv=Ftk1OWrq c=1 sm=1 tr=0 ts=6a426150 cx=c_pps a=1Os3MKEOqt8YzSjcPV0cFA==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=VwQbUJbxAAAA:8 a=pryAGsrBFMLCAmXlw1UA:9 a=QEXdDO2ut3YA:10 a=hhpmQAJR8DioWGSBphRh:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI5MDEwMCBTYWx0ZWRfX0z7Y+w7TN4yE xFUkdPMfqwIlBhBMkXcS6Gl96/HOJ1Ix5Sorq6WGQgARHwSeeGXkBK68JJRNhpeJx4rnbFRhSbz ZRHuY7jOusPvsD6Pzt0oVGZ3ioesh38= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI5MDEwMCBTYWx0ZWRfX5seAV9OEVx/R dAqXTcS5enJLYlv9ww4CUrwtrX/PIKNghbitH/NbEkyjoAN4O6v3C59/6oxIWh+xWSqrHGS74qj VbJEW2cnad0qnzI/iXbJgYeUv8d1p1OK0TG+qjVMZnhxbDNYVhKyW80Zmm2cpVxuBhqNssJEgxf tokk/JnWKPMaYGasAMgmlsNdmHx2QyERSRSX1MKM+Ozj2FeSR+vRnZaPo+Uyj5MTQ37IkJA3lwM FDjbQIVYd7eVwx1n5C9aVVI/Pboobkkrh77jdREMQgliNaRWR75yxGKPMUJ7kz2l3Vrqugd5M61 2CTKFEEFI+p67zSMWa8c6Y5v9tTTVrALuLddFUVe3jIhtUboFenoZkwnd+8/xhsKSB1cgpS1/Lb wMKQmQnVPyLhJfI2JMCjAtp1qbF5u5n9HLBWlC1aF1PFusv4eZWyBDifVFSKAraxkJ/UejUBJz2 fkd8RLuCT5lqitMCW4A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-29_03,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 phishscore=0 priorityscore=1501 malwarescore=0 spamscore=0 clxscore=1015 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606290100 On 6/25/26 12:16 AM, Kamal Wadhwa wrote: > On Tue, Jun 16, 2026 at 01:48:50PM +0200, Konrad Dybcio wrote: >> On 5/15/26 1:16 PM, Kamal Wadhwa wrote: >>> On Wed, Jan 28, 2026 at 12:32:09AM +0530, Saikiran wrote: >>>> This series adds support for the standard `regulator-off-on-delay-us` >>>> property to the Qualcomm RPMh regulator driver and updates the >>>> corresponding Device Tree bindings. >>>> >>>> Motivation: >>>> On the Lenovo Yoga Slim 7x (Snapdragon X Elite), the camera regulators >>>> (LDO1, LDO3, LDO7) have large bulk capacitors and rely on passive discharge. >>>> When these regulators are disabled, the voltage decays very slowly. If >>>> re-enabled too quickly, the sensor experiences a brownout and fails to >>>> initialize. >>>> >>>> Verification: >>>> I verified that the core `drivers/regulator/of_regulator.c` does not >>>> currently parse `regulator-off-on-delay-us` in `of_get_regulation_constraints()`. >>>> Therefore, the driver must parse this property explicitly and populate >>>> `rdesc->off_on_delay` so the regulator core can enforce the constraint. >>>> >>>> Changes in v3: >>>> - Added Patch 1/2: Update DT bindings to allow `regulator-off-on-delay-us` >>>> for `qcom,rpmh-regulator` (Requested by Mark Brown). >>>> - Updated Patch 2/2: Refined commit message to explicitly mention the >>>> passive discharge and bulk capacitor mechanism on the Yoga Slim 7x >>>> (Requested by Mark Brown). >>>> >>>> Changes in v2: >>>> - Moved the motivation/context from the cover letter into the commit >>>> message of the driver patch. >>>> >>>> Saikiran (2): >>>> dt-bindings: regulator: qcom,rpmh: Allow regulator-off-on-delay-us >>>> regulator: qcom-rpmh: Add support for regulator-off-on-delay-us >>> >>> Hi Mark, Bjorn, Konrad and all, >>> >>> We have another UFS issue on QCS8300 RB4 EVK, where it seems this patch is >>> helping. >>> >>> Issue is seen 2/10 reboots and it happens in the UFS probe defer path: >>> >>> 1. UFS probe takes regulator handle for VCC(vreg_l8a) of UFS host controller. >>> 2. UFS probe enables the regulator >>> 3. UFS probe defers (due to some other dependency un-related to regulator) >>> 4. UFS regulator disabled on probe exit >>> 5. UFS re-attempts probe and re-enables the regulator >>> 6. UFS init sequence runs -> UFS NOP OUT command failed (no shell) >>> >>> Issue Log: >>> >>> [ 6.583836] ufshcd-qcom 1d84000.ufs: ufshcd_verify_dev_init: NOP OUT failed -11 >>> [ 6.592780] ufshcd-qcom 1d84000.ufs: ufshcd_async_scan failed: -11 >>> >>> NOTE >>> - Issue is not seen in first probe attempt, because UFS regulators are left ON >>> from bootloader, which gives enough time between rail turn ON and UFS init >>> sequence start. However in issue case, it seems re-probe is happening too >>> fast, which causes init sequence to fail and UFS brownouts (similar to camera >>> sensor case) >>> >>> - Also, we compared this board with other RBxx EVK boards for UFS rail, it >>> seems that this board has more caps on the VCC regulator, as the board is >>> designed to have both EMMC and UFS, and we have DT option to pick one of them. >>> >>> So for EMMC those extra caps were added and they are impacting rampup on VCC. >>> >>> Since this is not entirely a UFS part issue, but a board design constraint, it >>> seems better if we handle this in the regulator side itself, as adding it in the >>> UFS driver may not be acceptable from UFS reviewers. >>> >>> Please share your opinion, if this seems to be good reason to accept this patch? >> >> Is that board in production already, or is that something that can be fixed? > > yes, it cannot be fixed in HW, as the board is already in production. Re-reading this thread, RobH's worry here: https://lore.kernel.org/all/20260129174829.GA1324020-robh@kernel.org/ seems to be misguided - AFAICU this property would be set on each regulator separately, not globally for all regulators under a given PMIC - is that right? In that case, I see no real downside in allowing that, especially given it would/should be used sparingly and only in cases like you mentioned where the board has some quirks Konrad