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Thu, 05 Feb 2026 01:34:00 -0800 (PST) Received: from hu-krichai-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8241d487886sm6181538b3a.59.2026.02.05.01.33.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Feb 2026 01:34:00 -0800 (PST) From: Krishna Chaitanya Chundru To: andersson@kernel.org, robh@kernel.org, mani@kernel.org, krzk@kernel.org, helgaas@kernel.org Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, lpieralisi@kernel.org, kw@linux.com, conor+dt@kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree-spec@vger.kernel.org, krishna.chundru@oss.qualcomm.com, lukas@wunner.de Subject: [PATCH v4] schemas: pci: Document PCIe T_POWER_ON Date: Thu, 5 Feb 2026 15:03:46 +0530 Message-Id: <20260205093346.667898-1-krishna.chundru@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Authority-Analysis: v=2.4 cv=Oc2VzxTY c=1 sm=1 tr=0 ts=6984640a cx=c_pps a=Oh5Dbbf/trHjhBongsHeRQ==:117 a=ZePRamnt/+rB5gQjfz0u9A==:17 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=ji1uk-MP7uB9YWhOYAAA:9 a=_Vgx9l1VpLgwpw_dHYaR:22 X-Proofpoint-ORIG-GUID: SQ5Wt3f-bT1--0mzqoBVhQ0QOaZ8vVrf X-Proofpoint-GUID: SQ5Wt3f-bT1--0mzqoBVhQ0QOaZ8vVrf X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjA1MDA2OCBTYWx0ZWRfXw580x/k6wA8u yfQOc5HkMAqgFat0xV1z9g1D94q1gCMAERTZ4mklDQOtVs4GvOh8kGA5vyi5x1ZPINnn2cEyZ7S 7XkB2t6UYQ5I7W7eLVHIsvx8YXTbwhJBbcAjZhqVpWfkUFIwidL5HpTvXX5TNG/RuooMf2iidtB XTCDC8F+XzTukIB7l+F3PbCGEubKYlRwBz9iyQY9eSpLlLGGTjsnrVYJkTDPIPiuNbeA8x8z+oS ZeF0tFNxoeR8g/O2J8GyTasmf3n0pLiUIfRWc74HEsbNxx9AiXw8iJnffkmRLSvlLyrjmIwZ/kj aQbfzT76YQx0k0e5L9VLn10WXvFDVgc+3He4DQbRrskbmUmpxWMNjDBhw9CQOpSsXgVslcvSkNO 2xGrZ3dOdX0JCPmNbGa1XXLRVgs5b4Nbk8viRgEvSzoa63LcwFhBMR0QExxgMHZLaO3iLjxF2wX Jj16DtdsxYrjdAPbkjA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-05_01,2026-02-05_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 suspectscore=0 bulkscore=0 priorityscore=1501 spamscore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602050068 Content-Type: text/plain; charset="utf-8" From PCIe r7, sec 5.5.4 & Table 5-11 in sec 5.5.5 T_POWER_ON is the minimum amount of time (in us) that each component must wait in L1.2.Exit after sampling CLKREQ# asserted before actively driving the interface to ensure no device is ever actively driving into an unpowered component and these values are based on the components and AC coupling capacitors used in the connection linking the two components. This property should be used to indicate the T_POWER_ON and drivers using this property are responsible for programming both the scale and the value of T_POWER_ON to comply with the PCIe specification. Signed-off-by: Krishna Chaitanya Chundru Acked-by: Manivannan Sadhasivam --- Changes in V3. - Couple of nits from Mani & Bjorn. - Link to v3: https://lore.kernel.org/all/20251126103112.838549-1-krishna.c= hundru@oss.qualcomm.com/ Changes in v2: - Move the property to pci-device.yaml so that it will be applicable to endpoint devices also (Mani). - Use latest spec (Lukas) - Link to v2: https://lore.kernel.org/all/20251110112947.2071036-1-krishna.= chundru@oss.qualcomm.com/ Changes in v1: - Updated the commiit text (Mani). - Link to v1: https://lore.kernel.org/all/20251110112550.2070659-1-krishna.= chundru@oss.qualcomm.com/#t dtschema/schemas/pci/pci-device.yaml | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/dtschema/schemas/pci/pci-device.yaml b/dtschema/schemas/pci/pc= i-device.yaml index ca094a0..a847500 100644 --- a/dtschema/schemas/pci/pci-device.yaml +++ b/dtschema/schemas/pci/pci-device.yaml @@ -63,6 +63,15 @@ properties: description: GPIO controlled connection to WAKE# signal maxItems: 1 =20 + t-power-on-us: + description: + The minimum amount of time that each component must wait in + L1.2.Exit after sampling CLKREQ# asserted before actively driving + the interface to ensure no device is ever actively driving into an + unpowered component. This value is based on the components and AC + coupling capacitors used in the connection linking the two + components (PCIe r7.0, sec 5.5.4). + required: - reg =20 --=20 2.34.1