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Subject[PATCH v5 01/14] PCI: Add pcie_get_speed_cap() to find max supported link speed
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From: Tal Gilboa <talgi@mellanox.com>

Add pcie_get_speed_cap() to find the max link speed supported by a device.
Change max_link_speed_show() to use pcie_get_speed_cap().

Signed-off-by: Tal Gilboa <talgi@mellanox.com>
[bhelgaas: return speed directly instead of error and *speed, don't export
outside drivers/pci]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
---
drivers/pci/pci-sysfs.c | 28 ++--------------------------
drivers/pci/pci.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
drivers/pci/pci.h | 10 ++++++++++
3 files changed, 56 insertions(+), 26 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7dc5be545d18..c2ea05fbbf1d 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -158,33 +158,9 @@ static DEVICE_ATTR_RO(resource);
static ssize_t max_link_speed_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- struct pci_dev *pci_dev = to_pci_dev(dev);
- u32 linkcap;
- int err;
- const char *speed;
-
- err = pcie_capability_read_dword(pci_dev, PCI_EXP_LNKCAP, &linkcap);
- if (err)
- return -EINVAL;
-
- switch (linkcap & PCI_EXP_LNKCAP_SLS) {
- case PCI_EXP_LNKCAP_SLS_16_0GB:
- speed = "16 GT/s";
- break;
- case PCI_EXP_LNKCAP_SLS_8_0GB:
- speed = "8 GT/s";
- break;
- case PCI_EXP_LNKCAP_SLS_5_0GB:
- speed = "5 GT/s";
- break;
- case PCI_EXP_LNKCAP_SLS_2_5GB:
- speed = "2.5 GT/s";
- break;
- default:
- speed = "Unknown speed";
- }
+ struct pci_dev *pdev = to_pci_dev(dev);

- return sprintf(buf, "%s\n", speed);
+ return sprintf(buf, "%s\n", PCIE_SPEED2STR(pcie_get_speed_cap(pdev)));
}
static DEVICE_ATTR_RO(max_link_speed);

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index f6a4dd10d9b0..b29d3436ee9f 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5146,6 +5146,50 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed,
}
EXPORT_SYMBOL(pcie_get_minimum_link);

+/**
+ * pcie_get_speed_cap - query for the PCI device's link speed capability
+ * @dev: PCI device to query
+ *
+ * Query the PCI device speed capability. Return the maximum link speed
+ * supported by the device.
+ */
+enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev)
+{
+ u32 lnkcap2, lnkcap;
+
+ /*
+ * PCIe r4.0 sec 7.5.3.18 recommends using the Supported Link
+ * Speeds Vector in Link Capabilities 2 when supported, falling
+ * back to Max Link Speed in Link Capabilities otherwise.
+ */
+ pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
+ if (lnkcap2) { /* PCIe r3.0-compliant */
+ if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_16_0GB)
+ return PCIE_SPEED_16_0GT;
+ else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_8_0GB)
+ return PCIE_SPEED_8_0GT;
+ else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_5_0GB)
+ return PCIE_SPEED_5_0GT;
+ else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_2_5GB)
+ return PCIE_SPEED_2_5GT;
+ return PCI_SPEED_UNKNOWN;
+ }
+
+ pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+ if (lnkcap) {
+ if (lnkcap & PCI_EXP_LNKCAP_SLS_16_0GB)
+ return PCIE_SPEED_16_0GT;
+ else if (lnkcap & PCI_EXP_LNKCAP_SLS_8_0GB)
+ return PCIE_SPEED_8_0GT;
+ else if (lnkcap & PCI_EXP_LNKCAP_SLS_5_0GB)
+ return PCIE_SPEED_5_0GT;
+ else if (lnkcap & PCI_EXP_LNKCAP_SLS_2_5GB)
+ return PCIE_SPEED_2_5GT;
+ }
+
+ return PCI_SPEED_UNKNOWN;
+}
+
/**
* pci_select_bars - Make BAR mask from the type of resource
* @dev: the PCI device for which BAR mask is made
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fcd81911b127..1186d8be6055 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -253,6 +253,16 @@ bool pci_bus_clip_resource(struct pci_dev *dev, int idx);
void pci_reassigndev_resource_alignment(struct pci_dev *dev);
void pci_disable_bridge_window(struct pci_dev *dev);

+/* PCIe link information */
+#define PCIE_SPEED2STR(speed) \
+ ((speed) == PCIE_SPEED_16_0GT ? "16 GT/s" : \
+ (speed) == PCIE_SPEED_8_0GT ? "8 GT/s" : \
+ (speed) == PCIE_SPEED_5_0GT ? "5 GT/s" : \
+ (speed) == PCIE_SPEED_2_5GT ? "2.5 GT/s" : \
+ "Unknown speed")
+
+enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev);
+
/* Single Root I/O Virtualization */
struct pci_sriov {
int pos; /* Capability position */
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