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Wed, 23 Sep 2026 00:23:24 -0700 From: Manikanta Maddireddy To: Lorenzo Pieralisi , Krzysztof Wilczynski , Manivannan Sadhasivam , "Bjorn Helgaas" , CC: Rob Herring , Thierry Reding , Jonathan Hunter , Kishon Vijay Abraham I , Frank Li , Vidya Sagar , Niklas Cassel , Koichiro Den , Marco Crivellari , "Andy Shevchenko" , , , "Manikanta Maddireddy" Subject: [PATCH 06/11] PCI: tegra194: Check for L1SS capability before programming Date: Wed, 23 Sep 2026 12:52:32 +0530 Message-ID: <20260923072237.1139013-7-mmaddireddy@nvidia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260923072237.1139013-1-mmaddireddy@nvidia.com> References: <20260923072237.1139013-1-mmaddireddy@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00002310:EE_|SA1PR12MB7200:EE_ X-MS-Office365-Filtering-Correlation-Id: 5f2c3d5b-8ca6-4bf0-c0c0-08df194398b7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|376014|1800799024|82310400026|7416014|36860700016|10067099003|6133799003|11063799006|18002099003|22082099003|56012099006; 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If the capability is absent, the code writes offsets from zero instead of L1SS registers. Check for the L1SS capability before programming L1SS-specific fields. Keep RAS-DES discovery, ASPM counter enablement and AFR latency programming outside that guard because they do not depend on L1SS. Only create the ASPM counter debugfs file when the RAS-DES capability is present. Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support") Signed-off-by: Manikanta Maddireddy --- drivers/pci/controller/dwc/pcie-tegra194.c | 72 ++++++++++++---------- 1 file changed, 41 insertions(+), 31 deletions(-) diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c index 358156c63da0..b35d9456e9de 100644 --- a/drivers/pci/controller/dwc/pcie-tegra194.c +++ b/drivers/pci/controller/dwc/pcie-tegra194.c @@ -673,37 +673,46 @@ static void init_host_aspm(struct tegra_pcie_dw *pcie) pcie->ras_des_cap = dw_pcie_find_ext_capability(&pcie->pci, PCI_EXT_CAP_ID_VNDR); - - /* Enable ASPM counters */ - val = FIELD_PREP(EVENT_COUNTER_ENABLE_MASK, EVENT_COUNTER_ENABLE_ALL); - val |= FIELD_PREP(EVENT_COUNTER_GROUP_SEL_MASK, EVENT_COUNTER_GROUP_5); - dw_pcie_writel_dbi(pci, pcie->ras_des_cap + - PCIE_RAS_DES_EVENT_COUNTER_CONTROL, val); - - /* Program T_cmrt and T_pwr_on values */ - val = dw_pcie_readl_dbi(pci, l1ss + PCI_L1SS_CAP); - FIELD_MODIFY(PCI_L1SS_CAP_CM_RESTORE_TIME, &val, pcie->aspm_cmrt); - FIELD_MODIFY(PCI_L1SS_CAP_P_PWR_ON_VALUE, &val, pcie->aspm_pwr_on_t); - dw_pcie_writel_dbi(pci, l1ss + PCI_L1SS_CAP, val); - - if (pcie->supports_clkreq) - pci->l1ss_support = true; - - /* - * Disable L1.2 capability advertisement for Tegra234 Endpoint mode. - * Tegra234 has a hardware bug where during L1.2 exit, the UPHY PLL is - * powered up immediately without waiting for REFCLK to stabilize. This - * causes the PLL to fail to lock to the correct frequency, resulting in - * PCIe link loss. Since there is no hardware fix available, we prevent - * the Endpoint from advertising L1.2 support by clearing the L1.2 bits - * in the L1 PM Substates Capabilities register. This ensures the host - * will not attempt to enter L1.2 state with this Endpoint. - */ - if (pcie->of_data->disable_l1_2 && - pcie->of_data->mode == DW_PCIE_EP_TYPE) { + if (pcie->ras_des_cap) { + /* Enable ASPM counters */ + val = FIELD_PREP(EVENT_COUNTER_ENABLE_MASK, + EVENT_COUNTER_ENABLE_ALL); + val |= FIELD_PREP(EVENT_COUNTER_GROUP_SEL_MASK, + EVENT_COUNTER_GROUP_5); + dw_pcie_writel_dbi(pci, pcie->ras_des_cap + + PCIE_RAS_DES_EVENT_COUNTER_CONTROL, val); + } + + if (l1ss) { + /* Program T_cmrt and T_pwr_on values */ val = dw_pcie_readl_dbi(pci, l1ss + PCI_L1SS_CAP); - val &= ~(PCI_L1SS_CAP_PCIPM_L1_2 | PCI_L1SS_CAP_ASPM_L1_2); + FIELD_MODIFY(PCI_L1SS_CAP_CM_RESTORE_TIME, &val, + pcie->aspm_cmrt); + FIELD_MODIFY(PCI_L1SS_CAP_P_PWR_ON_VALUE, &val, + pcie->aspm_pwr_on_t); dw_pcie_writel_dbi(pci, l1ss + PCI_L1SS_CAP, val); + + if (pcie->supports_clkreq) + pci->l1ss_support = true; + + /* + * Disable L1.2 capability advertisement for Tegra234 Endpoint + * mode. Tegra234 has a hardware bug where during L1.2 exit, + * the UPHY PLL is powered up immediately without waiting for + * REFCLK to stabilize. This causes the PLL to fail to lock to + * the correct frequency, resulting in PCIe link loss. Since + * there is no hardware fix available, prevent the Endpoint + * from advertising L1.2 support by clearing the L1.2 bits in + * the L1 PM Substates Capabilities register. This ensures the + * host will not attempt to enter L1.2 with this Endpoint. + */ + if (pcie->of_data->disable_l1_2 && + pcie->of_data->mode == DW_PCIE_EP_TYPE) { + val = dw_pcie_readl_dbi(pci, l1ss + PCI_L1SS_CAP); + val &= ~(PCI_L1SS_CAP_PCIPM_L1_2 | + PCI_L1SS_CAP_ASPM_L1_2); + dw_pcie_writel_dbi(pci, l1ss + PCI_L1SS_CAP, val); + } } /* Program L0s and L1 entrance latencies */ @@ -727,8 +736,9 @@ static void init_debugfs(struct tegra_pcie_dw *pcie) pcie->debugfs = debugfs_create_dir(name, NULL); - debugfs_create_devm_seqfile(dev, "aspm_state_cnt", pcie->debugfs, - aspm_state_cnt); + if (pcie->ras_des_cap) + debugfs_create_devm_seqfile(dev, "aspm_state_cnt", pcie->debugfs, + aspm_state_cnt); } #else static inline void init_host_aspm(struct tegra_pcie_dw *pcie) { return; } -- 2.34.1