PCIe spec 5.0 r1.0 section 2.2.6.2 says:
If an Endpoint supports sending Requests to other Endpoints (as
opposed to host memory), the Endpoint must not send 10-Bit Tag
Requests to another given Endpoint unless an implementation-specific
mechanism determines that the Endpoint supports 10-Bit Tag Completer
capability.
Add a 10bit_tag sysfs file, write 0 to disable 10-Bit Tag Requester
when the driver does not bind the device. The typical use case is for
p2pdma when the peer device does not support 10-Bit Tag Completer.
Write 1 to enable 10-Bit Tag Requester when RC supports 10-Bit Tag
Completer capability. The typical use case is for host memory targeted
by DMA Requests. The 10bit_tag file content indicate current status of
10-Bit Tag Requester Enable.
Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-pci | 18 +++++-
drivers/pci/pci-sysfs.c | 78 +++++++++++++++++++++++++
drivers/pci/pci.h | 2 +
drivers/pci/probe.c | 14 +++++
4 files changed, 111 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index d4ae03296861..0c26346d1069 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -156,7 +156,7 @@ Description:
binary file containing the Vital Product Data for the
device. It should follow the VPD format defined in
PCI Specification 2.1 or 2.2, but users should consider
- that some devices may have incorrectly formatted data.
+ that some devices may have incorrectly formatted data.
If the underlying VPD has a writable section then the
corresponding section of this file will be writable.
@@ -424,3 +424,19 @@ Description:
The file is writable if the PF is bound to a driver that
implements ->sriov_set_msix_vec_count().
+
+What: /sys/bus/pci/devices/.../10bit_tag
+Date: September 2021
+Contact: Dongdong Liu <liudongdong3@xxxxxxxxxx>
+Description:
+ The file will be visible when the device supports 10-Bit Tag
+ Requester. The file is readable, the value indicate current
+ status of 10-Bit Tag Requester Enable.
+ 1 - enabled, 0 - disabled.
+
+ The file is also writable, write 0 to disable 10-Bit Tag
+ Requester when the driver does not bind the device. The typical
+ use case is for p2pdma when the peer device does not support
+ 10-Bit Tag Completer. Write 1 to enable 10-Bit Tag Requester
+ when RC supports 10-Bit Tag Completer capability. The typical
+ use case is for host memory targeted by DMA Requests.
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7fb5cd17cc98..f571e4a0eb4c 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -306,6 +306,55 @@ static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
}
static DEVICE_ATTR_RW(enable);
+static ssize_t pci_10bit_tag_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ bool enable;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (kstrtobool(buf, &enable) < 0)
+ return -EINVAL;
+
+ if (pdev->driver)
+ return -EBUSY;
+
+ if (!pcie_rp_10bit_tag_cmp_supported(pdev))
+ return -EPERM;
+
+ if (enable)
+ pcie_capability_set_word(pdev, PCI_EXP_DEVCTL2,
+ PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
+ else
+ pcie_capability_clear_word(pdev, PCI_EXP_DEVCTL2,
+ PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
+
+ return count;
+}
+
+static ssize_t pci_10bit_tag_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct pci_dev *pdev = to_pci_dev(dev);
+ u16 ctl;
+ int ret;
+
+ ret = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL2, &ctl);
+ if (ret)
+ return -EINVAL;
+
+ return sysfs_emit(buf, "%u\n",
+ !!(ctl & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN));
+}
+
+static struct device_attribute dev_attr_10bit_tag = __ATTR(10bit_tag, 0644,
+ pci_10bit_tag_show,
+ pci_10bit_tag_store);
+
#ifdef CONFIG_NUMA
static ssize_t numa_node_store(struct device *dev,
struct device_attribute *attr, const char *buf,
@@ -635,6 +684,11 @@ static struct attribute *pcie_dev_attrs[] = {
NULL,
};
+static struct attribute *pcie_dev_10bit_tag_attrs[] = {
+ &dev_attr_10bit_tag.attr,
+ NULL,
+};
+
static struct attribute *pcibus_attrs[] = {
&dev_attr_bus_rescan.attr,
&dev_attr_cpuaffinity.attr,
@@ -1482,6 +1536,24 @@ static umode_t pcie_dev_attrs_are_visible(struct kobject *kobj,
return 0;
}
+static umode_t pcie_dev_10bit_tag_attrs_is_visible(struct kobject *kobj,
+ struct attribute *a, int n)
+{
+ struct device *dev = kobj_to_dev(kobj);
+ struct pci_dev *pdev = to_pci_dev(dev);
+
+ if (pdev->is_virtfn)
+ return 0;
+
+ if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT)
+ return 0;
+
+ if (!(pdev->devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_REQ))
+ return 0;
+
+ return a->mode;
+}
+
static const struct attribute_group pci_dev_group = {
.attrs = pci_dev_attrs,
};
@@ -1522,6 +1594,11 @@ static const struct attribute_group pcie_dev_attr_group = {
.is_visible = pcie_dev_attrs_are_visible,
};
+static const struct attribute_group pcie_dev_10bit_tag_attr_group = {
+ .attrs = pcie_dev_10bit_tag_attrs,
+ .is_visible = pcie_dev_10bit_tag_attrs_is_visible,
+};
+
static const struct attribute_group *pci_dev_attr_groups[] = {
&pci_dev_attr_group,
&pci_dev_hp_attr_group,
@@ -1531,6 +1608,7 @@ static const struct attribute_group *pci_dev_attr_groups[] = {
#endif
&pci_bridge_attr_group,
&pcie_dev_attr_group,
+ &pcie_dev_10bit_tag_attr_group,
#ifdef CONFIG_PCIEAER
&aer_stats_attr_group,
#endif
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 1cce56c2aea0..f719a41dfc7f 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -264,6 +264,8 @@ struct device *pci_get_host_bridge_device(struct pci_dev *dev);
void pci_put_host_bridge_device(struct device *dev);
int pci_configure_extended_tags(struct pci_dev *dev, void *ign);
+bool pcie_rp_10bit_tag_cmp_supported(struct pci_dev *dev);
+
bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
int crs_timeout);
bool pci_bus_generic_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 7259ad774ac8..705dd4e85df5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2042,6 +2042,20 @@ static void pci_configure_mps(struct pci_dev *dev)
p_mps, mps, mpss);
}
+bool pcie_rp_10bit_tag_cmp_supported(struct pci_dev *dev)
+{
+ struct pci_dev *root;
+
+ root = pcie_find_root_port(dev);
+ if (!root)
+ return false;
+
+ if (!(root->devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP))
+ return false;
+
+ return true;
+}
+
int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
{
struct pci_host_bridge *host;
--
2.22.0
