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authorJesse Barnes <jbarnes@virtuousgeek.org>2011-01-14 17:53:04 +0100
committerJesse Barnes <jbarnes@virtuousgeek.org>2011-05-12 00:18:53 +0200
commit51c2e0a7e5bc7ed1384cc68cfb95e702571500c9 (patch)
tree839dc5d6eb233b009c8802cb8cafde68f5a2ce6e /drivers/pci/pci.c
parentPCI: add OBFF enable/disable support (diff)
downloadlinux-51c2e0a7e5bc7ed1384cc68cfb95e702571500c9.tar.xz
linux-51c2e0a7e5bc7ed1384cc68cfb95e702571500c9.zip
PCI: add latency tolerance reporting enable/disable support
Latency tolerance reporting allows devices to send messages to the root complex indicating their latency tolerance for snooped & unsnooped memory transactions. Add support for enabling & disabling this feature, along with a routine to set the max latencies a device should send upstream. Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Diffstat (limited to 'drivers/pci/pci.c')
-rw-r--r--drivers/pci/pci.c149
1 files changed, 149 insertions, 0 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 01e4cab2e5cb..53302cbdb94c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1979,6 +1979,155 @@ void pci_disable_obff(struct pci_dev *dev)
}
EXPORT_SYMBOL(pci_disable_obff);
+/**
+ * pci_ltr_supported - check whether a device supports LTR
+ * @dev: PCI device
+ *
+ * RETURNS:
+ * True if @dev supports latency tolerance reporting, false otherwise.
+ */
+bool pci_ltr_supported(struct pci_dev *dev)
+{
+ int pos;
+ u32 cap;
+
+ if (!pci_is_pcie(dev))
+ return false;
+
+ pos = pci_pcie_cap(dev);
+ if (!pos)
+ return false;
+
+ pci_read_config_dword(dev, pos + PCI_EXP_DEVCAP2, &cap);
+
+ return cap & PCI_EXP_DEVCAP2_LTR;
+}
+EXPORT_SYMBOL(pci_ltr_supported);
+
+/**
+ * pci_enable_ltr - enable latency tolerance reporting
+ * @dev: PCI device
+ *
+ * Enable LTR on @dev if possible, which means enabling it first on
+ * upstream ports.
+ *
+ * RETURNS:
+ * Zero on success, errno on failure.
+ */
+int pci_enable_ltr(struct pci_dev *dev)
+{
+ int pos;
+ u16 ctrl;
+ int ret;
+
+ if (!pci_ltr_supported(dev))
+ return -ENOTSUPP;
+
+ pos = pci_pcie_cap(dev);
+ if (!pos)
+ return -ENOTSUPP;
+
+ /* Only primary function can enable/disable LTR */
+ if (PCI_FUNC(dev->devfn) != 0)
+ return -EINVAL;
+
+ /* Enable upstream ports first */
+ if (dev->bus) {
+ ret = pci_enable_ltr(dev->bus->self);
+ if (ret)
+ return ret;
+ }
+
+ pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
+ ctrl |= PCI_EXP_LTR_EN;
+ pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
+
+ return 0;
+}
+EXPORT_SYMBOL(pci_enable_ltr);
+
+/**
+ * pci_disable_ltr - disable latency tolerance reporting
+ * @dev: PCI device
+ */
+void pci_disable_ltr(struct pci_dev *dev)
+{
+ int pos;
+ u16 ctrl;
+
+ if (!pci_ltr_supported(dev))
+ return;
+
+ pos = pci_pcie_cap(dev);
+ if (!pos)
+ return;
+
+ /* Only primary function can enable/disable LTR */
+ if (PCI_FUNC(dev->devfn) != 0)
+ return;
+
+ pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
+ ctrl &= ~PCI_EXP_LTR_EN;
+ pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
+}
+EXPORT_SYMBOL(pci_disable_ltr);
+
+static int __pci_ltr_scale(int *val)
+{
+ int scale = 0;
+
+ while (*val > 1023) {
+ *val = (*val + 31) / 32;
+ scale++;
+ }
+ return scale;
+}
+
+/**
+ * pci_set_ltr - set LTR latency values
+ * @dev: PCI device
+ * @snoop_lat_ns: snoop latency in nanoseconds
+ * @nosnoop_lat_ns: nosnoop latency in nanoseconds
+ *
+ * Figure out the scale and set the LTR values accordingly.
+ */
+int pci_set_ltr(struct pci_dev *dev, int snoop_lat_ns, int nosnoop_lat_ns)
+{
+ int pos, ret, snoop_scale, nosnoop_scale;
+ u16 val;
+
+ if (!pci_ltr_supported(dev))
+ return -ENOTSUPP;
+
+ snoop_scale = __pci_ltr_scale(&snoop_lat_ns);
+ nosnoop_scale = __pci_ltr_scale(&nosnoop_lat_ns);
+
+ if (snoop_lat_ns > PCI_LTR_VALUE_MASK ||
+ nosnoop_lat_ns > PCI_LTR_VALUE_MASK)
+ return -EINVAL;
+
+ if ((snoop_scale > (PCI_LTR_SCALE_MASK >> PCI_LTR_SCALE_SHIFT)) ||
+ (nosnoop_scale > (PCI_LTR_SCALE_MASK >> PCI_LTR_SCALE_SHIFT)))
+ return -EINVAL;
+
+ pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+ if (!pos)
+ return -ENOTSUPP;
+
+ val = (snoop_scale << PCI_LTR_SCALE_SHIFT) | snoop_lat_ns;
+ ret = pci_write_config_word(dev, pos + PCI_LTR_MAX_SNOOP_LAT, val);
+ if (ret != 4)
+ return -EIO;
+
+ val = (nosnoop_scale << PCI_LTR_SCALE_SHIFT) | nosnoop_lat_ns;
+ ret = pci_write_config_word(dev, pos + PCI_LTR_MAX_NOSNOOP_LAT, val);
+ if (ret != 4)
+ return -EIO;
+
+ return 0;
+}
+EXPORT_SYMBOL(pci_set_ltr);
+
static int pci_acs_enable;
/**