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Tue, 25 Feb 2025 03:45:48 -0800 (PST) X-Google-Smtp-Source: AGHT+IFLEK0CZlrCWZb3Xuj6wszq4+kfT30Don9arlTNNmJDccEr1jdH+78HFestoRn7PlNMxSiSVg== X-Received: by 2002:a05:6a00:8a17:b0:732:6a48:22f6 with SMTP id d2e1a72fcca58-7341410bb54mr27637467b3a.9.1740483948142; Tue, 25 Feb 2025 03:45:48 -0800 (PST) Received: from hu-krichai-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7347a7f9bb1sm1331790b3a.92.2025.02.25.03.45.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 03:45:47 -0800 (PST) From: Krishna Chaitanya Chundru Date: Tue, 25 Feb 2025 17:15:05 +0530 Subject: [PATCH v7 2/4] PCI: of: Add API to retrieve equalization presets from device tree Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250225-preset_v6-v7-2-a593f3ef3951@oss.qualcomm.com> References: <20250225-preset_v6-v7-0-a593f3ef3951@oss.qualcomm.com> In-Reply-To: <20250225-preset_v6-v7-0-a593f3ef3951@oss.qualcomm.com> To: Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Helgaas , Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , =?utf-8?q?Krzysztof_Wilczy=C5=84?= =?utf-8?q?ski?= Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, quic_mrana@quicinc.com, quic_vbadigan@quicinc.com, Krishna Chaitanya Chundru X-Mailer: b4 0.14.1 X-Developer-Signature: v=1; a=ed25519-sha256; t=1740483933; l=4572; i=krishna.chundru@oss.qualcomm.com; s=20230907; h=from:subject:message-id; bh=WMbOp27utSDkHhEXVAa3MHd/brdszfrzIwpx9Festsw=; b=dvX/auMBkpEgcGMORcBFgKOMtMkGSfVdVDfd6RF5iHlRcUBHnUXDQewFhufkMjDqeQhHJRWNB jOnND8g2ITtD1TzdG8zKakZMSC8tLm649lBS+5oJDId0yqYbdZJVByp X-Developer-Key: i=krishna.chundru@oss.qualcomm.com; a=ed25519; pk=10CL2pdAKFyzyOHbfSWHCD0X0my7CXxj8gJScmn1FAg= X-Proofpoint-ORIG-GUID: EeGa7VgcwHBUUqAzBVKy9GVhbZy5guwY X-Proofpoint-GUID: EeGa7VgcwHBUUqAzBVKy9GVhbZy5guwY X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-25_04,2025-02-25_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxlogscore=999 malwarescore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 adultscore=0 spamscore=0 bulkscore=0 mlxscore=0 priorityscore=1501 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502250082 PCIe equalization presets are predefined settings used to optimize signal integrity by compensating for signal loss and distortion in high-speed data transmission. As per PCIe spec 6.0.1 revision section 8.3.3.3 & 4.2.4 for data rates of 8.0 GT/s, 16.0 GT/s, 32.0 GT/s, and 64.0 GT/s, there is a way to configure lane equalization presets for each lane to enhance the PCIe link reliability. Each preset value represents a different combination of pre-shoot and de-emphasis values. For each data rate, different registers are defined: for 8.0 GT/s, registers are defined in section 7.7.3.4; for 16.0 GT/s, in section 7.7.5.9, etc. The 8.0 GT/s rate has an extra receiver preset hint, requiring 16 bits per lane, while the remaining data rates use 8 bits per lane. Based on the number of lanes and the supported data rate, this function reads the device tree property and stores in the presets structure. Signed-off-by: Krishna Chaitanya Chundru --- drivers/pci/of.c | 43 +++++++++++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 27 ++++++++++++++++++++++++++- 2 files changed, 69 insertions(+), 1 deletion(-) diff --git a/drivers/pci/of.c b/drivers/pci/of.c index 7a806f5c0d20..9ebe7d0e4e0c 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c @@ -851,3 +851,46 @@ u32 of_pci_get_slot_power_limit(struct device_node *node, return slot_power_limit_mw; } EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit); + +/** + * of_pci_get_equalization_presets - Parses the "eq-presets-Ngts" property. + * + * @dev: Device containing the properties. + * @presets: Pointer to store the parsed data. + * @num_lanes: Maximum number of lanes supported. + * + * If the property is present read and store the data in the preset structure + * else assign default value 0xff to indicate property is not present. + * + * Return: 0 if the property is not available or successfully parsed; errno otherwise. + */ +int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes) +{ + char name[20]; + int ret; + + presets->eq_presets_8gts[0] = PCI_EQ_RESV; + ret = of_property_read_u16_array(dev->of_node, "eq-presets-8gts", + presets->eq_presets_8gts, num_lanes); + if (ret && ret != -EINVAL) { + dev_err(dev, "Error reading eq-presets-8gts :%d\n", ret); + return ret; + } + + for (int i = 0; i < EQ_PRESET_TYPE_MAX; i++) { + presets->eq_presets_Ngts[i][0] = PCI_EQ_RESV; + snprintf(name, sizeof(name), "eq-presets-%dgts", 8 << (i + 1)); + ret = of_property_read_u8_array(dev->of_node, name, + presets->eq_presets_Ngts[i], + num_lanes); + if (ret && ret != -EINVAL) { + dev_err(dev, "Error reading %s :%d\n", name, ret); + return ret; + } + } + + return 0; +} +EXPORT_SYMBOL_GPL(of_pci_get_equalization_presets); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 01e51db8d285..c8d44b21ef03 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -9,6 +9,8 @@ struct pcie_tlp_log; /* Number of possible devfns: 0.0 to 1f.7 inclusive */ #define MAX_NR_DEVFNS 256 +#define MAX_NR_LANES 16 + #define PCI_FIND_CAP_TTL 48 #define PCI_VSEC_ID_INTEL_TBT 0x1234 /* Thunderbolt */ @@ -808,6 +810,20 @@ static inline u64 pci_rebar_size_to_bytes(int size) struct device_node; +#define PCI_EQ_RESV 0xff + +enum equalization_preset_type { + EQ_PRESET_TYPE_16GTS, + EQ_PRESET_TYPE_32GTS, + EQ_PRESET_TYPE_64GTS, + EQ_PRESET_TYPE_MAX +}; + +struct pci_eq_presets { + u16 eq_presets_8gts[MAX_NR_LANES]; + u8 eq_presets_Ngts[EQ_PRESET_TYPE_MAX][MAX_NR_LANES]; +}; + #ifdef CONFIG_OF int of_get_pci_domain_nr(struct device_node *node); int of_pci_get_max_link_speed(struct device_node *node); @@ -822,7 +838,9 @@ void pci_release_bus_of_node(struct pci_bus *bus); int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge); bool of_pci_supply_present(struct device_node *np); - +int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes); #else static inline int of_get_pci_domain_nr(struct device_node *node) @@ -867,6 +885,13 @@ static inline bool of_pci_supply_present(struct device_node *np) { return false; } + +static inline int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes) +{ + return 0; +} #endif /* CONFIG_OF */ struct of_changeset;