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Fri, 25 Sep 2020 22:29:28 -0700 (PDT) From: Puranjay Mohan To: bjorn@helgaas.com Date: Sat, 26 Sep 2020 10:59:17 +0530 Message-Id: <20200926052917.20247-1-puranjay12@gmail.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Cc: linux-pci@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Puranjay Mohan Subject: [Linux-kernel-mentees] [PATCH v5] PCI: Add support for LTR X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" Add a new function pci_ltr_init() which will be called from pci_init_capabilities() to initialize every PCIe device's LTR values. Add code in probe.c to evaluate LTR _DSM and save the latencies in pci_dev. Signed-off-by: Puranjay Mohan --- v5 - Add static keyword with pci_ltr_encode() and pci_ltr_decode() v4 - remove pci_upstream_bridge and use acpi_pci_find_companion() to get the handle for evaluating _DSM. Add acpi_check_dsm() Change the logging mechanism. v3 - change the algorithm to add latencies, add helper funtions for encoding and decoding the latencies. v2 - add an #ifdefin pci-acpi.c to fix the bug reported by test bot. v1 - based the patch on v5.9-rc1 so it applies correctly. --- drivers/pci/pci-acpi.c | 37 ++++++++++++++++ drivers/pci/pci.c | 96 ++++++++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 3 ++ drivers/pci/probe.c | 6 +++ include/linux/pci-acpi.h | 1 + include/linux/pci.h | 2 + 6 files changed, 145 insertions(+) diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c index d5869a03f748..1bceee861bfc 100644 --- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -1213,6 +1213,43 @@ static void pci_acpi_optimize_delay(struct pci_dev *pdev, ACPI_FREE(obj); } +/* pci_acpi_evaluate_ltr_latency + * + * @dev - the pci_dev to evaluate and save latencies + */ +void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev) +{ +#ifdef CONFIG_PCIEASPM + struct acpi_device *adev; + union acpi_object *obj, *elements; + + adev = ACPI_COMPANION(&dev->dev); + if (!adev && !pci_dev_is_added(dev)) + adev = acpi_pci_find_companion(&dev->dev); + if (!adev) + return; + + if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid, 2, + 1ULL << DSM_PCI_LTR_MAX_LATENCY)) + return; + obj = acpi_evaluate_dsm(adev->handle, &pci_acpi_dsm_guid, 2, + DSM_PCI_LTR_MAX_LATENCY, NULL); + if (!obj) + return; + + if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 4) { + elements = obj->package.elements; + dev->max_snoop_latency = (u16)elements[1].integer.value | + ((u16)elements[0].integer.value << + PCI_LTR_SCALE_SHIFT); + dev->max_nosnoop_latency = (u16)elements[3].integer.value | + ((u16)elements[2].integer.value << + PCI_LTR_SCALE_SHIFT); + } + ACPI_FREE(obj); +#endif +} + static void pci_acpi_set_external_facing(struct pci_dev *dev) { u8 val; diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index a458c46d7e39..fc6ba515135b 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3056,6 +3056,102 @@ void pci_pm_init(struct pci_dev *dev) dev->imm_ready = 1; } +/** + * pci_ltr_decode - Decode the latency to a value in ns + * @latency: latency according to PCIe base specification 7.8.2. + */ +static u64 pci_ltr_decode(u16 latency) +{ + u16 scale = (latency & PCI_LTR_SCALE_MASK) >> 10; + u16 value = latency & PCI_LTR_VALUE_MASK; + + switch (scale) { + case 0: return value; + case 1: return value * 32; + case 2: return value * 1024; + case 3: return value * 32768; + case 4: return value * 1048576; + case 5: return value * 33554432; + } + return 0; +} + +/** + * pci_ltr_encode - Encode the value in ns to a 16 bit register value + * @val: latency according to PCIe base specification 7.8.2. + */ +static u16 pci_ltr_encode(u64 val) +{ + if (val <= 1UL * 0x3ff) + return (0 << 10) | (val & 0x3ff); + if (val <= 32UL * 0x3ff) + return (1 << 10) | ((val >> 5) & 0x3ff); + if (val <= 1024UL * 0x3ff) + return (2 << 10) | ((val >> 10) & 0x3ff); + if (val <= 32768UL * 0x3ff) + return (3 << 10) | ((val >> 15) & 0x3ff); + if (val <= 1048576UL * 0x3ff) + return (4 << 10) | ((val >> 20) & 0x3ff); + if (val <= 33554432UL * 0x3ff) + return (5 << 10) | ((val >> 25) & 0x3ff); + return 0; +} + +/** + * pci_ltr_init - Initialize Latency Tolerance Information of given PCI device + * @dev: PCI device to handle. + */ +void pci_ltr_init(struct pci_dev *dev) +{ +#ifdef CONFIG_PCIEASPM + struct pci_dev *bridge = dev; + int ltr; + u64 max_snoop = 0, max_nosnoop = 0; + u16 max_snoop_encoded, max_nosnoop_encoded; + u16 max_snoop_current, max_nosnoop_current; + u64 max_snoop_current_decoded, max_nosnoop_current_decoded; + + ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR); + if (!ltr) + return; + + bridge = pci_upstream_bridge(bridge); + while (bridge) { + max_snoop += pci_ltr_decode(bridge->max_snoop_latency); + max_nosnoop += pci_ltr_decode(bridge->max_nosnoop_latency); + bridge = pci_upstream_bridge(bridge); + } + max_snoop_encoded = pci_ltr_encode(max_snoop); + max_nosnoop_encoded = pci_ltr_encode(max_nosnoop); + + pci_read_config_word(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, + &max_snoop_current); + max_snoop_current_decoded = pci_ltr_decode(max_snoop_current); + pci_read_config_word(dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, + &max_nosnoop_current); + max_nosnoop_current_decoded = pci_ltr_decode(max_nosnoop_current); + + pci_dbg(dev, + "Calculated Max Snoop Latency %lluns Max No-Snoop Latency %lluns\n", + max_snoop, max_nosnoop); + + if (max_snoop != max_snoop_current_decoded) { + pci_info(dev, "Max Snoop Latency %lluns (was %lluns)\n", + max_snoop, max_snoop_current_decoded); + pci_write_config_word(dev, + ltr + PCI_LTR_MAX_SNOOP_LAT, + max_snoop_encoded); + } + if (max_nosnoop != max_nosnoop_current_decoded) { + pci_info(dev, "Max No-Snoop Latency %lluns (was %lluns)\n", + max_nosnoop, max_nosnoop_current_decoded); + pci_write_config_word(dev, + ltr + PCI_LTR_MAX_NOSNOOP_LAT, + max_nosnoop_encoded); + } +#endif +} + static unsigned long pci_ea_flags(struct pci_dev *dev, u8 prop) { unsigned long flags = IORESOURCE_PCI_FIXED | IORESOURCE_PCI_EA_BEI; diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index fa12f7cbc1a0..18890975d0f1 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -110,6 +110,7 @@ void pci_free_cap_save_buffers(struct pci_dev *dev); bool pci_bridge_d3_possible(struct pci_dev *dev); void pci_bridge_d3_update(struct pci_dev *dev); void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev); +void pci_ltr_init(struct pci_dev *dev); static inline void pci_wakeup_event(struct pci_dev *dev) { @@ -680,11 +681,13 @@ static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL #ifdef CONFIG_ACPI int pci_acpi_program_hp_params(struct pci_dev *dev); +void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev); #else static inline int pci_acpi_program_hp_params(struct pci_dev *dev) { return -ENODEV; } +static inline void pci_acpi_evaluate_ltr_latency(struct pci_dev *dev) {} #endif #ifdef CONFIG_PCIEASPM diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 03d37128a24f..d5039ccf11a8 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2105,6 +2105,11 @@ static void pci_configure_ltr(struct pci_dev *dev) if (!pci_is_pcie(dev)) return; + /* + * Read latency values from _DSM and save in pci_dev + * as a part of latency tolerance reporting mechanism. + */ + pci_acpi_evaluate_ltr_latency(dev); pcie_capability_read_dword(dev, PCI_EXP_DEVCAP2, &cap); if (!(cap & PCI_EXP_DEVCAP2_LTR)) @@ -2400,6 +2405,7 @@ static void pci_init_capabilities(struct pci_dev *dev) pci_ptm_init(dev); /* Precision Time Measurement */ pci_aer_init(dev); /* Advanced Error Reporting */ pci_dpc_init(dev); /* Downstream Port Containment */ + pci_ltr_init(dev); /* Latency Tolerance Reporting */ pcie_report_downtraining(dev); diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h index 5ba475ca9078..e23236a4ff66 100644 --- a/include/linux/pci-acpi.h +++ b/include/linux/pci-acpi.h @@ -110,6 +110,7 @@ extern const guid_t pci_acpi_dsm_guid; /* _DSM Definitions for PCI */ #define DSM_PCI_PRESERVE_BOOT_CONFIG 0x05 +#define DSM_PCI_LTR_MAX_LATENCY 0x06 #define DSM_PCI_DEVICE_NAME 0x07 #define DSM_PCI_POWER_ON_RESET_DELAY 0x08 #define DSM_PCI_DEVICE_READINESS_DURATIONS 0x09 diff --git a/include/linux/pci.h b/include/linux/pci.h index 835530605c0d..af7558e3c331 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -380,6 +380,8 @@ struct pci_dev { struct pcie_link_state *link_state; /* ASPM link state */ unsigned int ltr_path:1; /* Latency Tolerance Reporting supported from root to here */ + u16 max_snoop_latency; /* LTR Max Snoop latency */ + u16 max_nosnoop_latency; /* LTR Max No-Snoop latency */ #endif unsigned int eetlp_prefix_path:1; /* End-to-End TLP Prefix */ -- 2.27.0 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees