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Tue, 16 Jun 2026 04:48:53 -0700 (PDT) X-Received: by 2002:a05:620a:171f:b0:915:2b2b:fbdc with SMTP id af79cd13be357-9161bace098mr1809782085a.2.1781610533341; Tue, 16 Jun 2026 04:48:53 -0700 (PDT) Received: from [192.168.120.170] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-bfdb442083esm637095066b.3.2026.06.16.04.48.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Jun 2026 04:48:52 -0700 (PDT) Message-ID: <06a264d0-6a14-4b71-b783-82b771f04411@oss.qualcomm.com> Date: Tue, 16 Jun 2026 13:48:50 +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 , Saikiran , broonie@kernel.org, monish.chunara@oss.qualcomm.com, jishnu.prakash@oss.qualcomm.com, nitin.rawat@oss.qualcomm.com, Bjorn Andersson Cc: 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> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20260515111647.qg75thdvcbvvjpoi@hu-kamalw-hyd.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: AH2mYg44r6inZ72cPlilFDOoqirYLGFu X-Proofpoint-ORIG-GUID: AH2mYg44r6inZ72cPlilFDOoqirYLGFu X-Authority-Analysis: v=2.4 cv=Ibi3n2qa c=1 sm=1 tr=0 ts=6a313826 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=tAkNNTVKMvv2VOvRsoYA:9 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE2MDEyMCBTYWx0ZWRfX6UmM3TOu45hy N44ME831RnrL2A93MFNjunjHn4wQdUQRRj9aDCSx1K7Y3hiTgc9LC99kE73Tvwu44lb1rfsK1Rg i0q0hgOf0vFKebhMQb94B/FULqWqmIkY3396Y86sTqzXlGvI6YXDJLglCnGYh0h2tBVnMaXXlT7 26U5Us7FgYCrvQ7JRtt9ObdsPYqxE7LzMl+YiKweB7tupzctl7ONXzlA9CNY0Uoy5aDa407b/aE sHziceQ8pFJljw/KaMKQcTYT90EhsjKKVnJMRSKkOfSl+traFYpg041Ms6nol/b7klDZt479OeL C91gGupK2TnCOh2TmUXxY/ZoCRb4c6kspjrUHGTPDk5vZsAYWQgBaRB0Ej4PMJ6KAUOY75MwVD8 jijlpRAYMt/ZjX1JYa+TIbdgkngCw+d5w11ZU7GpkOh3CZ3+RRoUpzRnSvVeVRfUt+d7BUQV7om gFuvYHZMKJa9K9xlqeg== X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE2MDEyMCBTYWx0ZWRfX+yS7ufjPjFN+ 0PC2CJE+8uQoqnpz8uV03WlC93ZUp+V5fufWTHovApForDlJbStHiHyx8MgwI7WcfPQ8QDTvdUE +0GMhENA1RwcuYlljn0XosDErVHLKxQ= 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=2026-06-16_03,2026-06-15_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 lowpriorityscore=0 impostorscore=0 spamscore=0 malwarescore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606040000 definitions=main-2606160120 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? Konrad