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 <puranjay12@xxxxxxxxx>
---
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 | 30 ++++++++++++++++++++++++++++++
drivers/pci/pci.c | 27 +++++++++++++++++++++++++++
drivers/pci/pci.h | 5 +++++
drivers/pci/probe.c | 6 ++++++
include/linux/pci-acpi.h | 1 +
include/linux/pci.h | 2 ++
6 files changed, 71 insertions(+)
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index d5869a03f748..af8297040c38 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1213,6 +1213,36 @@ 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_PCIASPM
+ union acpi_object *obj, *elements;
+ struct acpi_device *handle;
+
+ handle = ACPI_HANDLE(&dev->dev);
+ if (!handle)
+ return;
+
+ obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, 0x2,
+ 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..b5531272b865 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3056,6 +3056,33 @@ void pci_pm_init(struct pci_dev *dev)
dev->imm_ready = 1;
}
+/**
+ * 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_PCIASPM
+ int ltr;
+ struct pci_dev *endpoint_dev = dev;
+ u16 max_snoop_sum = 0;
+ u16 max_nosnoop_sum = 0;
+
+ ltr = pci_find_ext_capability(endpoint_dev, PCI_EXT_CAP_ID_LTR);
+ if (!ltr)
+ return;
+
+ dev = pci_upstream_bridge(dev);
+ while (dev) {
+ max_snoop_sum += dev->max_snoop_latency;
+ max_nosnoop_sum += dev->max_nosnoop_latency;
+ dev = pci_upstream_bridge(dev);
+ }
+ pci_write_config_word(endpoint_dev, ltr + PCI_LTR_MAX_SNOOP_LAT, max_snoop_sum);
+ pci_write_config_word(endpoint_dev, ltr + PCI_LTR_MAX_NOSNOOP_LAT, max_nosnoop_sum);
+#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..ef3d22b82200 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 +681,15 @@ 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..0257aa615665 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2140,6 +2140,11 @@ static void pci_configure_ltr(struct pci_dev *dev)
dev->ltr_path = 1;
}
#endif
+
+ /*
+ * Read latency values from _DSM and save in pci_dev
+ */
+ pci_acpi_evaluate_ltr_latency(dev);
}
static void pci_configure_eetlp_prefix(struct pci_dev *dev)
@@ -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..9de6b290ed81 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
