[RFC PATCH v2 2/4] PCI/doe: Initial support PCI Data Object Exchange

Jonathan Cameron
2021-04-13T16:03:39Z

Introduced in a PCI ECN [1], DOE provides a config space
based mailbox with standard protocol discovery. Each mailbox
is accessed through a DOE PCIE Extended Capability.

A device may have 1 or more DOE mailboxes, each of which is allowed
to support any number of protocols (some DOE protocols
specifications apply additional restrictions). A given protocol
may be supported on more than one DOE mailbox on a given function.

If a driver wishes to access any number of DOE instances / protocols
it makes a single call to pcie_doe_register_all() which will find
available DOEs, create the required infrastructure and cache the
protocols they support. pcie_doe_find() can then retrieve a
pointer to an appropriate DOE instance.

Testing conducted against QEMU using:

https://lore.kernel.org/qemu-devel/1612900760-7361-1-git-send-email-cbrowy@avery-design.com/
+ fix for interrupt flag mentioned in that thread and a whole load
of hacks to exercise error paths etc.

[1] https://members.pcisig.com/wg/PCI-SIG/document/14143

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---

Thanks to Dan Williams for reviewing v1.
Note code has changed a lot, so I may well have missed stuff in this
log. Details on approaches to the DOE serialization discussed in
the cover letter.

Changes since v1:
Major stuff:
* Rework the registration of DOE. DOE instances are added to a list in
the struct pci_dev. A single call to pcie_doe_register_all() finds
all DOEs present on a device and caches which protocols they support.
The lifetime of these can then all be managed alongside the
struct pci_dev avoiding need for reference counting etc whilst allowing
a driver not to care if different protocols are using the same DOE
instance, or different ones. The driver issues a call to
pcie_doe_find() to get a pointer to the first appropriate DOE.
Note, a side effect of minimizing impact of this on struct pci_dev
is that we can't build DOE support as a module.
* Instead of serializing on a mutex, move to a more complex state machine
based scheme in which the DOE config space registers are only
accessed from a single delayed work item. The state machine uses
two states for normal operation, IDLE and WAITING. Two states also
exist for ABORT to indicate if it was called in response to error,
or at startup. Interrupts result in mod_delayed_work()
to force an immediate check on the status register.
Message queuing is implemented with a list of tasks and kicking
the state machine work item as needed.
* Decide, inside the core DOE code, whether to poll based
on if the MSI/MSIX interrupts are enabled and the DOE
instance advertises an interrupt.
* Define a struct pcie_doe_exchange to encapsulate header info
with payloads etc. Specific fields used for VID and protocol +
lengths so the DOE header can be constructed inside the DOE
functions rather than relying on callers to do that.
* Don't hide away devm_ stuff in calls that don't make it obvious.

Minor stuff:
* pcie_doe_init() and pcie_doe_register separation to cover the
bits that can fail in register() and the bits that can't in init()
* Many typos
* Rename cap_offset field to cap
* Use new PCI_VENDOR_ID_PCI_SIG define to avoid open coding the
value
* Add defines for timeouts etc.
* Missing EXPORT_SYMBOL_GPL() added to allow DOE access from
modules.

drivers/pci/pcie/Kconfig | 8 +
drivers/pci/pcie/Makefile | 1 +
drivers/pci/pcie/doe.c | 590 ++++++++++++++++++++++++++++++++++
include/linux/pci.h | 3 +
include/linux/pcie-doe.h | 85 +++++
include/uapi/linux/pci_regs.h | 29 +-
6 files changed, 715 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
index 45a2ef702b45..1b566d08bfef 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -142,3 +142,11 @@ config PCIE_EDR
the PCI Firmware Specification r3.2. Enable this if you want to
support hybrid DPC model which uses both firmware and OS to
implement DPC.
+
+config PCIE_DOE
+ bool
+ help
+ This enables library support PCI Data Object Exchange capability.
+ DOE provides a simple mailbox in PCI express config space that is
+ used by a number of different protocols.
+ It is defined in the Data Object Exchange ECN to PCI 5.0.
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index b2980db88cc0..801fdd5fbfc1 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_PCIE_PME) += pme.o
obj-$(CONFIG_PCIE_DPC) += dpc.o
obj-$(CONFIG_PCIE_PTM) += ptm.o
obj-$(CONFIG_PCIE_EDR) += edr.o
+obj-$(CONFIG_PCIE_DOE) += doe.o
diff --git a/drivers/pci/pcie/doe.c b/drivers/pci/pcie/doe.c
new file mode 100644
index 000000000000..b8a27c744d09
--- /dev/null
+++ b/drivers/pci/pcie/doe.c
@@ -0,0 +1,590 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Data Object Exchange ECN
+ * https://members.pcisig.com/wg/PCI-SIG/document/14143
+ *
+ * Copyright (C) 2021 Huawei
+ * Jonathan Cameron <Jonathan.Cameron@huawei.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/jiffies.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/pcie-doe.h>
+#include <linux/workqueue.h>
+
+#define PCI_DOE_PROTOCOL_DISCOVERY 0
+
+#define PCI_DOE_BUSY_MAX_RETRIES 16
+#define PCI_DOE_POLL_INTERVAL (HZ / 128)
+
+/* Timeout of 1 second from 6.xx.1 ECN - Data Object Exchange */
+#define PCI_DOE_TIMEOUT HZ
+
+static irqreturn_t pcie_doe_irq(int irq, void *data)
+{
+ struct pcie_doe *doe = data;
+ struct pci_dev *pdev = doe->pdev;
+ u32 val;
+
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_STATUS, &val);
+ if (FIELD_GET(PCI_DOE_STATUS_INT_STATUS, val)) {
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_STATUS, val);
+ mod_delayed_work(system_wq, &doe->statemachine, 0);
+ return IRQ_HANDLED;
+ }
+ /* Leave the error case to be handled outside irq */
+ if (FIELD_GET(PCI_DOE_STATUS_ERROR, val)) {
+ mod_delayed_work(system_wq, &doe->statemachine, 0);
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+/*
+ * Only call when safe to directly access the DOE, either because no tasks
+ * yet queued, or called from doe_statemachine_work() which has exclusive
+ * access to the DOE config space.
+ */
+static void pcie_doe_abort_start(struct pcie_doe *doe)
+{
+ struct pci_dev *pdev = doe->pdev;
+
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_CTRL,
+ PCI_DOE_CTRL_ABORT);
+
+ doe->timeout_jiffies = jiffies + HZ;
+ schedule_delayed_work(&doe->statemachine, HZ);
+}
+
+static int pcie_doe_send_req(struct pcie_doe *doe, struct pcie_doe_exchange *ex)
+{
+ struct pci_dev *pdev = doe->pdev;
+ u32 val;
+ int i;
+
+ /*
+ * Check the DOE busy bit is not set.
+ * If it is set, this could indicate someone other than Linux is
+ * using the mailbox.
+ */
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_STATUS, &val);
+ if (FIELD_GET(PCI_DOE_STATUS_BUSY, val))
+ return -EBUSY;
+
+ if (FIELD_GET(PCI_DOE_STATUS_ERROR, val))
+ return -EIO;
+
+ /* Write DOE Header */
+ val = FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_VID, ex->vid) |
+ FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, ex->protocol);
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_WRITE, val);
+ /* Length is 2 DW of header + length of payload in DW */
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_WRITE,
+ FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH,
+ 2 + ex->request_pl_sz / 4));
+ for (i = 0; i < ex->request_pl_sz / 4; i++)
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_WRITE,
+ ex->request_pl[i]);
+
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_CTRL, PCI_DOE_CTRL_GO);
+ /* Request is sent - now wait for poll or irq */
+ return 0;
+}
+
+static int pcie_doe_recv_resp(struct pcie_doe *doe, struct pcie_doe_exchange *ex)
+{
+ struct pci_dev *pdev = doe->pdev;
+ size_t length;
+ u32 val;
+ int i;
+
+ /* Read the first two dwords to get the length and protocol */
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_READ, &val);
+ if ((FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_VID, val) != ex->vid) ||
+ (FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, val) != ex->protocol)) {
+ dev_err(&pdev->dev, "Expected [VID, Protocol] = [%x, %x], got [%x, %x]\n",
+ ex->vid, ex->protocol,
+ FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_VID, val),
+ FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, val));
+ return -EIO;
+ }
+
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_READ, 0);
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_READ, &val);
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_READ, 0);
+
+ length = FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH, val);
+ if (length > SZ_1M)
+ return -EIO;
+
+ /* Read the rest of the response payload */
+ for (i = 0; i < min(length, ex->response_pl_sz / 4); i++) {
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_READ,
+ &ex->response_pl[i]);
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_READ, 0);
+ }
+
+ /* Flush excess length */
+ for (; i < length; i++) {
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_READ, &val);
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_READ, 0);
+ }
+ /* Final error check to pick up on any since Data Object Ready */
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_STATUS, &val);
+ if (FIELD_GET(PCI_DOE_STATUS_ERROR, val))
+ return -EIO;
+
+ return min(length, ex->response_pl_sz / 4) * 4;
+}
+
+static void pcie_doe_task_complete(void *private)
+{
+ complete(private);
+}
+
+/**
+ * struct pcie_doe_task - description of a query / response task
+ * @h: Head to add it to the list of outstanding tasks.
+ * @ex: The info details of the task to be done.
+ * @rv: Return value. Length of received response or error.
+ * @cb: Callback for completion of task.
+ * @private: Private data passed to callback on completion.
+ */
+struct pcie_doe_task {
+ struct list_head h;
+ struct pcie_doe_exchange *ex;
+ int rv;
+ void (*cb)(void *private);
+ void *private;
+};
+
+/**
+ * pcie_doe_sync() - Send a request, then wait for and receive response.
+ * @doe: DOE mailbox state structure
+ * @ex: Description of the buffers and vid, type used in this
+ * request/response pair
+ *
+ * Excess data will be discarded.
+ *
+ * Return: payload in bytes on success, < 0 on error
+ */
+int pcie_doe_sync(struct pcie_doe *doe, struct pcie_doe_exchange *ex)
+{
+ struct pcie_doe_task task;
+ DECLARE_COMPLETION_ONSTACK(c);
+ bool only_task;
+
+ /* DOE requests must be a whole number of DW */
+ if (ex->request_pl_sz % sizeof(u32))
+ return -EINVAL;
+
+ task.ex = ex;
+ task.cb = pcie_doe_task_complete;
+ task.private = &c;
+
+ mutex_lock(&doe->tasks_lock);
+ if (doe->dead) {
+ mutex_unlock(&doe->tasks_lock);
+ return -EIO;
+ }
+ only_task = list_empty(&doe->tasks);
+ list_add_tail(&task.h, &doe->tasks);
+ if (only_task)
+ schedule_delayed_work(&doe->statemachine, 0);
+ mutex_unlock(&doe->tasks_lock);
+ wait_for_completion(&c);
+
+ return task.rv;
+}
+
+static void doe_statemachine_work(struct work_struct *work)
+{
+ struct delayed_work *w = to_delayed_work(work);
+ struct pcie_doe *doe = container_of(w, struct pcie_doe, statemachine);
+ struct pci_dev *pdev = doe->pdev;
+ struct pcie_doe_task *task;
+ bool abort;
+ u32 val;
+ int rc;
+
+ mutex_lock(&doe->tasks_lock);
+ task = list_first_entry_or_null(&doe->tasks, struct pcie_doe_task, h);
+ abort = doe->abort;
+ doe->abort = false;
+ mutex_unlock(&doe->tasks_lock);
+
+ if (abort) {
+ /*
+ * Currently only used during init - care needed if we want to generally
+ * expose pcie_doe_abort() as it would impact queries in flight.
+ */
+ WARN_ON(task);
+ doe->state = DOE_WAIT_ABORT;
+ pcie_doe_abort_start(doe);
+ return;
+ }
+
+ switch (doe->state) {
+ case DOE_IDLE:
+ if (task == NULL)
+ return;
+
+ /* Nothing currently in flight so queue a task */
+ rc = pcie_doe_send_req(doe, task->ex);
+ /*
+ * The specification does not provide any guidance on how long some other
+ * entity could keep the DOE busy, so try for 1 second then fail.
+ * Busy handling is best effort only, because there is not way of avoiding
+ * racing against another user of the DOE.
+ */
+ if (rc == -EBUSY) {
+ doe->busy_retries++;
+ if (doe->busy_retries == PCI_DOE_BUSY_MAX_RETRIES) {
+ /* Long enough, fail this request */
+ doe->busy_retries = 0;
+ goto busy;
+ }
+ schedule_delayed_work(w, HZ / PCI_DOE_BUSY_MAX_RETRIES);
+ return;
+ }
+ if (rc)
+ goto abort;
+ doe->busy_retries = 0;
+
+ doe->state = DOE_WAIT_RESP;
+ doe->timeout_jiffies = jiffies + HZ;
+ /* Now poll or wait for IRQ with timeout */
+ if (doe->irq > 0)
+ schedule_delayed_work(w, PCI_DOE_TIMEOUT);
+ else
+ schedule_delayed_work(w, PCI_DOE_POLL_INTERVAL);
+ return;
+
+ case DOE_WAIT_RESP:
+ /* Not possible to get here with NULL task */
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_STATUS, &val);
+ if (FIELD_GET(PCI_DOE_STATUS_ERROR, val)) {
+ rc = -EIO;
+ goto abort;
+ }
+
+ if (!FIELD_GET(PCI_DOE_STATUS_DATA_OBJECT_READY, val)) {
+ /* If not yet at timeout reschedule otherwise abort */
+ if (time_after(jiffies, doe->timeout_jiffies)) {
+ rc = -ETIMEDOUT;
+ goto abort;
+ }
+ schedule_delayed_work(w, PCI_DOE_POLL_INTERVAL);
+ return;
+ }
+
+ rc = pcie_doe_recv_resp(doe, task->ex);
+ if (rc < 0)
+ goto abort;
+
+ doe->state = DOE_IDLE;
+
+ mutex_lock(&doe->tasks_lock);
+ list_del(&task->h);
+ if (!list_empty(&doe->tasks))
+ schedule_delayed_work(w, 0);
+ mutex_unlock(&doe->tasks_lock);
+
+ /* Set the return value to the length of received payload */
+ task->rv = rc;
+ task->cb(task->private);
+ return;
+
+ case DOE_WAIT_ABORT:
+ case DOE_WAIT_ABORT_ON_ERR:
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_STATUS, &val);
+
+ if (!FIELD_GET(PCI_DOE_STATUS_ERROR, val) &&
+ !FIELD_GET(PCI_DOE_STATUS_BUSY, val)) {
+ /* Back to normal state - carry on */
+ mutex_lock(&doe->tasks_lock);
+ if (!list_empty(&doe->tasks))
+ schedule_delayed_work(w, 0);
+ mutex_unlock(&doe->tasks_lock);
+
+ /* For deliberately triggered abort, someone is waiting */
+ if (doe->state == DOE_WAIT_ABORT)
+ complete(&doe->abort_c);
+ doe->state = DOE_IDLE;
+
+ return;
+ }
+ if (time_after(jiffies, doe->timeout_jiffies)) {
+ struct pcie_doe_task *t, *n;
+
+ /* We are dead - abort all queued tasks */
+ dev_err(&pdev->dev, "DOE ABORT timed out\n");
+ mutex_lock(&doe->tasks_lock);
+ doe->dead = true;
+ list_for_each_entry_safe(t, n, &doe->tasks, h) {
+ t->rv = -EIO;
+ t->cb(t->private);
+ list_del(&t->h);
+ }
+
+ mutex_unlock(&doe->tasks_lock);
+ if (doe->state == DOE_WAIT_ABORT)
+ complete(&doe->abort_c);
+ }
+ return;
+ }
+
+abort:
+ pcie_doe_abort_start(doe);
+ doe->state = DOE_WAIT_ABORT_ON_ERR;
+busy:
+ mutex_lock(&doe->tasks_lock);
+ list_del(&task->h);
+ mutex_unlock(&doe->tasks_lock);
+
+ task->rv = rc;
+ task->cb(task->private);
+ /* If we got here via busy, and the queue isn't empty then we need to go again */
+ if (doe->state == DOE_IDLE) {
+ mutex_lock(&doe->tasks_lock);
+ if (!list_empty(&doe->tasks))
+ schedule_delayed_work(w, 0);
+ mutex_unlock(&doe->tasks_lock);
+ }
+}
+
+static int pcie_doe_discovery(struct pcie_doe *doe, u8 *index, u16 *vid,
+ u8 *protocol)
+{
+ u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX, *index);
+ u32 response_pl;
+ struct pcie_doe_exchange ex = {
+ .vid = PCI_VENDOR_ID_PCI_SIG,
+ .protocol = PCI_DOE_PROTOCOL_DISCOVERY,
+ .request_pl = &request_pl,
+ .request_pl_sz = sizeof(request_pl),
+ .response_pl = &response_pl,
+ .response_pl_sz = sizeof(response_pl),
+ };
+ int ret;
+
+ ret = pcie_doe_sync(doe, &ex);
+ if (ret < 0)
+ return ret;
+
+ if (ret != sizeof(response_pl))
+ return -EIO;
+
+ *vid = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID, response_pl);
+ *protocol = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL, response_pl);
+ *index = FIELD_GET(PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX, response_pl);
+
+ return 0;
+}
+
+static int pcie_doe_cache_protocols(struct pcie_doe *doe)
+{
+ u8 index = 0;
+ int rc;
+
+ /* Discovery protocol must always be supported and must report itself */
+ doe->num_prots = 1;
+ doe->prots = kzalloc(sizeof(*doe->prots) * doe->num_prots, GFP_KERNEL);
+ if (doe->prots == NULL)
+ return -ENOMEM;
+
+ do {
+ struct pcie_doe_prot *prot, *prot_new;
+
+ prot = &doe->prots[doe->num_prots - 1];
+ rc = pcie_doe_discovery(doe, &index, &prot->vid, &prot->type);
+ if (rc)
+ goto free_prots;
+
+ if (index) {
+ prot_new = krealloc(doe->prots,
+ sizeof(*doe->prots) * doe->num_prots,
+ GFP_KERNEL);
+ if (prot_new == NULL) {
+ rc = -ENOMEM;
+ goto free_prots;
+ }
+ doe->prots = prot_new;
+ doe->num_prots++;
+ }
+ } while (index);
+
+ return 0;
+
+free_prots:
+ kfree(doe->prots);
+ return rc;
+}
+
+static void pcie_doe_init(struct pcie_doe *doe, struct pci_dev *pdev, int doe_offset)
+{
+ mutex_init(&doe->tasks_lock);
+ init_completion(&doe->abort_c);
+ doe->cap = doe_offset;
+ doe->pdev = pdev;
+ INIT_LIST_HEAD(&doe->tasks);
+ INIT_DELAYED_WORK(&doe->statemachine, doe_statemachine_work);
+}
+
+static int pcie_doe_abort(struct pcie_doe *doe)
+{
+ reinit_completion(&doe->abort_c);
+ mutex_lock(&doe->tasks_lock);
+ doe->abort = true;
+ mutex_unlock(&doe->tasks_lock);
+ schedule_delayed_work(&doe->statemachine, 0);
+ wait_for_completion(&doe->abort_c);
+
+ if (doe->dead)
+ return -EIO;
+
+ return 0;
+}
+
+static int pcie_doe_register(struct pcie_doe *doe)
+{
+ struct pci_dev *pdev = doe->pdev;
+ bool poll = !pci_dev_msi_enabled(pdev);
+ int rc, irq;
+ u32 val;
+
+ pci_read_config_dword(pdev, doe->cap + PCI_DOE_CAP, &val);
+
+ if (!poll && FIELD_GET(PCI_DOE_CAP_INT, val)) {
+ irq = pci_irq_vector(pdev, FIELD_GET(PCI_DOE_CAP_IRQ, val));
+ if (irq < 0)
+ return irq;
+
+ rc = request_irq(irq, pcie_doe_irq, 0, "DOE", doe);
+ if (rc)
+ return rc;
+
+ doe->irq = irq;
+ pci_write_config_dword(pdev, doe->cap + PCI_DOE_CTRL,
+ FIELD_PREP(PCI_DOE_CTRL_INT_EN, 1));
+ }
+
+ /* Reset the mailbox by issuing an abort */
+ rc = pcie_doe_abort(doe);
+ if (rc)
+ goto err_free_irqs;
+
+ return 0;
+
+err_free_irqs:
+ if (doe->irq > 0)
+ free_irq(doe->irq, doe);
+
+ return rc;
+}
+
+static void pcie_doe_unregister(struct pcie_doe *doe)
+{
+ if (doe->irq > 0)
+ free_irq(doe->irq, doe);
+}
+
+void pcie_doe_unregister_all(struct pci_dev *pdev)
+{
+ struct pcie_doe *doe, *next;
+
+ list_for_each_entry_safe(doe, next, &pdev->doe_list, h) {
+ /* First halt the state machine */
+ cancel_delayed_work_sync(&doe->statemachine);
+ kfree(doe->prots);
+ pcie_doe_unregister(doe);
+ kfree(doe);
+ }
+}
+EXPORT_SYMBOL_GPL(pcie_doe_unregister_all);
+
+/**
+ * pcie_doe_register_all() - Find and register all DOE mailboxes
+ * @pdev: PCI device whose DOE mailboxes we are finding.
+ *
+ * Will locate any DOE mailboxes present on the device and cache the
+ * protocols so that pcie_doe_find() can be used to retrieve a suitable DOE
+ * instance.
+ * DOE mailboxes are available until pcie_doe_unregister_all()
+ * is called.
+ *
+ * RETURNS: 0 on success, < 0 on error
+ */
+int pcie_doe_register_all(struct pci_dev *pdev)
+{
+ struct pcie_doe *doe;
+ int pos = 0;
+ int rc;
+
+ INIT_LIST_HEAD(&pdev->doe_list);
+
+ /* Walk the DOE extended capabilities and add to per pci_dev list */
+ while (true) {
+
+ pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_DOE);
+ if (!pos)
+ return 0;
+
+ doe = kzalloc(sizeof(*doe), GFP_KERNEL);
+ if (!doe) {
+ rc = -ENOMEM;
+ goto free_does;
+ }
+
+ pcie_doe_init(doe, pdev, pos);
+ rc = pcie_doe_register(doe);
+ if (rc) {
+ kfree(doe);
+ goto free_does;
+ }
+
+ rc = pcie_doe_cache_protocols(doe);
+ if (rc) {
+ pcie_doe_unregister(doe);
+ kfree(doe);
+ goto free_does;
+ }
+
+ list_add(&doe->h, &pdev->doe_list);
+ }
+
+free_does:
+ pcie_doe_unregister_all(pdev);
+
+ return rc;
+}
+EXPORT_SYMBOL_GPL(pcie_doe_register_all);
+
+/**
+ * pcie_doe_find() - Find the first DOE instance that supports a given protocol
+ * @pdev: Device on which to find the DOE instance.
+ * @vid: Vendor ID.
+ * @type: Specific protocol for this vendor.
+ *
+ * RETURNS: Pointer to DOE instance, or NULL if no suitable instance available.
+ */
+struct pcie_doe *pcie_doe_find(struct pci_dev *pdev, u16 vid, u8 type)
+{
+ struct pcie_doe *doe;
+ int i;
+
+ list_for_each_entry(doe, &pdev->doe_list, h) {
+ for (i = 0; i < doe->num_prots; i++)
+ if ((doe->prots[i].vid == vid) &&
+ (doe->prots[i].type == type))
+ return doe;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(pcie_doe_find);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 86c799c97b77..5d958a63e8c7 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -332,6 +332,9 @@ struct pci_dev {
#ifdef CONFIG_PCIEPORTBUS
struct rcec_ea *rcec_ea; /* RCEC cached endpoint association */
struct pci_dev *rcec; /* Associated RCEC device */
+#endif
+#ifdef CONFIG_PCIE_DOE
+ struct list_head doe_list; /* Data Object Exchange mailboxes */
#endif
u8 pcie_cap; /* PCIe capability offset */
u8 msi_cap; /* MSI capability offset */
diff --git a/include/linux/pcie-doe.h b/include/linux/pcie-doe.h
new file mode 100644
index 000000000000..794d6f090779
--- /dev/null
+++ b/include/linux/pcie-doe.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Object Exchange was added to the PCI spec as an ECN to 5.0.
+ *
+ * Copyright (C) 2021 Huawei
+ * Jonathan Cameron <Jonathan.Cameron@huawei.com>
+ */
+
+#include <linux/completion.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+
+#ifndef LINUX_PCIE_DOE_H
+#define LINUX_PCIE_DOE_H
+
+struct pcie_doe_prot {
+ u16 vid;
+ u8 type;
+};
+
+struct workqueue_struct;
+
+enum pcie_doe_state {
+ DOE_IDLE,
+ DOE_WAIT_RESP,
+ DOE_WAIT_ABORT,
+ DOE_WAIT_ABORT_ON_ERR,
+};
+
+struct pcie_doe_exchange {
+ u16 vid;
+ u8 protocol;
+ u32 *request_pl;
+ size_t request_pl_sz;
+ u32 *response_pl;
+ size_t response_pl_sz;
+};
+
+/**
+ * struct pcie_doe - State to support use of DOE mailbox
+ * @cap: Config space offset to base of DOE capability.
+ * @pdev: PCI device that hosts this DOE.
+ * @abort_c: Completion used for initial abort handling.
+ * @irq: Interrupt used for signaling DOE ready or abort.
+ * @prots: Cache of identifiers for protocols supported.
+ * @num_prots: Size of prots cache.
+ * @h: Used for DOE instance lifetime management.
+ * @wq: Workqueue used to handle state machine and polling / timeouts
+ * @tasks: List of task in flight + pending.
+ * @tasks_lock: Protect the tasks list.
+ * @statemachine: Work item for the DOE statemachine
+ * @state: Current state of this DOE.
+ * @timeout_jiffies: 1 second after GO set.
+ * @busy_retries: Count of retry attempts
+ * @abort: Request a manual abort (e.g. on init)
+ * @dead: Used to mark a DOE for which an ABORT has timed out.
+ * Further messages will immediately be aborted with error.
+ */
+struct pcie_doe {
+ int cap;
+ struct pci_dev *pdev;
+ struct completion abort_c;
+ int irq;
+ struct pcie_doe_prot *prots;
+ int num_prots;
+ struct list_head h;
+
+ struct workqueue_struct *wq;
+ struct list_head tasks;
+ struct mutex tasks_lock;
+ struct delayed_work statemachine;
+ enum pcie_doe_state state;
+ unsigned long timeout_jiffies;
+ unsigned int busy_retries;
+ bool abort;
+ bool dead;
+};
+
+int pcie_doe_register_all(struct pci_dev *pdev);
+void pcie_doe_unregister_all(struct pci_dev *pdev);
+struct pcie_doe *pcie_doe_find(struct pci_dev *pdev, u16 vid, u8 type);
+
+int pcie_doe_sync(struct pcie_doe *doe, struct pcie_doe_exchange *ex);
+
+#endif
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index e709ae8235e7..4d8a5fee2cdf 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -730,7 +730,8 @@
#define PCI_EXT_CAP_ID_DVSEC 0x23 /* Designated Vendor-Specific */
#define PCI_EXT_CAP_ID_DLF 0x25 /* Data Link Feature */
#define PCI_EXT_CAP_ID_PL_16GT 0x26 /* Physical Layer 16.0 GT/s */
-#define PCI_EXT_CAP_ID_MAX PCI_EXT_CAP_ID_PL_16GT
+#define PCI_EXT_CAP_ID_DOE 0x2E /* Data Object Exchange */
+#define PCI_EXT_CAP_ID_MAX PCI_EXT_CAP_ID_DOE

#define PCI_EXT_CAP_DSN_SIZEOF 12
#define PCI_EXT_CAP_MCAST_ENDPOINT_SIZEOF 40
@@ -1092,4 +1093,30 @@
#define PCI_PL_16GT_LE_CTRL_USP_TX_PRESET_MASK 0x000000F0
#define PCI_PL_16GT_LE_CTRL_USP_TX_PRESET_SHIFT 4

+/* Data Object Exchange */
+#define PCI_DOE_CAP 0x04 /* DOE Capabilities Register */
+#define PCI_DOE_CAP_INT 0x00000001 /* Interrupt Support */
+#define PCI_DOE_CAP_IRQ 0x00000ffe /* Interrupt Message Number */
+#define PCI_DOE_CTRL 0x08 /* DOE Control Register */
+#define PCI_DOE_CTRL_ABORT 0x00000001 /* DOE Abort */
+#define PCI_DOE_CTRL_INT_EN 0x00000002 /* DOE Interrupt Enable */
+#define PCI_DOE_CTRL_GO 0x80000000 /* DOE Go */
+#define PCI_DOE_STATUS 0x0C /* DOE Status Register */
+#define PCI_DOE_STATUS_BUSY 0x00000001 /* DOE Busy */
+#define PCI_DOE_STATUS_INT_STATUS 0x00000002 /* DOE Interrupt Status */
+#define PCI_DOE_STATUS_ERROR 0x00000004 /* DOE Error */
+#define PCI_DOE_STATUS_DATA_OBJECT_READY 0x80000000 /* Data Object Ready */
+#define PCI_DOE_WRITE 0x10 /* DOE Write Data Mailbox Register */
+#define PCI_DOE_READ 0x14 /* DOE Read Data Mailbox Register */
+
+/* DOE Data Object - note not actually registers */
+#define PCI_DOE_DATA_OBJECT_HEADER_1_VID 0x0000FFFF
+#define PCI_DOE_DATA_OBJECT_HEADER_1_TYPE 0x00FF0000
+#define PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH 0x0003FFFF
+
+#define PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX 0x000000FF
+#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID 0x0000FFFF
+#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL 0x00FF0000
+#define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX 0xFF000000
+
#endif /* LINUX_PCI_REGS_H */
--
2.19.1