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Date: Tue, 23 May 2023 10:09:27 -0700
From: Davidlohr Bueso <dave@...olabs.net>
To: dan.j.williams@...el.com
Cc: dave.jiang@...el.com, alison.schofield@...el.com,
vishal.l.verma@...el.com, ira.weiny@...el.com,
Jonathan.Cameron@...wei.com, fan.ni@...sung.com,
a.manzanares@...sung.com, dave@...olabs.net,
linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] cxl/mbox: Add background cmd handling machinery
This adds support for handling background operations, as defined in
the CXL 3.0 spec. Commands that can take too long (over ~2 seconds)
can run in the background asynchronously (to the hardware).
The driver will deal with such commands synchronously, blocking all
other incoming commands for a specified period of time, allowing
time-slicing the command such that the caller can send incremental
requests to avoid monopolizing the driver/device. Any out of sync
(timeout) between the driver and hardware is just disregarded as
an invalid state until the next successful submission. Such timeouts
are considered a rare occurrence, either a real device problem or a
driver issue that needs to reduce the size of the background operation
to fit the timeout.
On devices where mbox interrupts are supported, this will still use
a poller that will wakeup in the specified wait intervals. The irq
handler will simply awake the blocked cmd, which is also safe vs a
task that is either waking (timing out) or already awoken. Similarly
any irq setup error during the probing falls back to polling, thus
avoids unnecessarily erroring out.
Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
---
drivers/cxl/core/mbox.c | 3 +-
drivers/cxl/cxl.h | 8 ++++
drivers/cxl/cxlmem.h | 7 ++++
drivers/cxl/pci.c | 89 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 106 insertions(+), 1 deletion(-)
diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 2c8dc7e2b84d..5993261e3e08 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -220,7 +220,8 @@ int cxl_internal_send_cmd(struct cxl_dev_state *cxlds,
if (rc)
return rc;
- if (mbox_cmd->return_code != CXL_MBOX_CMD_RC_SUCCESS)
+ if (mbox_cmd->return_code != CXL_MBOX_CMD_RC_SUCCESS &&
+ mbox_cmd->return_code != CXL_MBOX_CMD_RC_BACKGROUND)
return cxl_mbox_cmd_rc2errno(mbox_cmd);
if (!out_size)
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index f93a28538962..ec69bda93aee 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -176,14 +176,22 @@ static inline int ways_to_eiw(unsigned int ways, u8 *eiw)
/* CXL 2.0 8.2.8.4 Mailbox Registers */
#define CXLDEV_MBOX_CAPS_OFFSET 0x00
#define CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK GENMASK(4, 0)
+#define CXLDEV_MBOX_CAP_BG_CMD_IRQ BIT(6)
+#define CXLDEV_MBOX_CAP_IRQ_MSGNUM_MASK GENMASK(10, 7)
#define CXLDEV_MBOX_CTRL_OFFSET 0x04
#define CXLDEV_MBOX_CTRL_DOORBELL BIT(0)
+#define CXLDEV_MBOX_CTRL_BG_CMD_IRQ BIT(2)
#define CXLDEV_MBOX_CMD_OFFSET 0x08
#define CXLDEV_MBOX_CMD_COMMAND_OPCODE_MASK GENMASK_ULL(15, 0)
#define CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK GENMASK_ULL(36, 16)
#define CXLDEV_MBOX_STATUS_OFFSET 0x10
+#define CXLDEV_MBOX_STATUS_BG_CMD BIT(0)
#define CXLDEV_MBOX_STATUS_RET_CODE_MASK GENMASK_ULL(47, 32)
#define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
+#define CXLDEV_MBOX_BG_CMD_COMMAND_OPCODE_MASK GENMASK_ULL(15, 0)
+#define CXLDEV_MBOX_BG_CMD_COMMAND_PCT_MASK GENMASK_ULL(22, 16)
+#define CXLDEV_MBOX_BG_CMD_COMMAND_RC_MASK GENMASK_ULL(47, 32)
+#define CXLDEV_MBOX_BG_CMD_COMMAND_VENDOR_MASK GENMASK_ULL(63, 48)
#define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
/*
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index a2845a7a69d8..1d8e81c87c6a 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -5,6 +5,7 @@
#include <uapi/linux/cxl_mem.h>
#include <linux/cdev.h>
#include <linux/uuid.h>
+#include <linux/rcuwait.h>
#include "cxl.h"
/* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
@@ -108,6 +109,9 @@ static inline struct cxl_ep *cxl_ep_load(struct cxl_port *port,
* variable sized output commands, it tells the exact number of bytes
* written.
* @min_out: (input) internal command output payload size validation
+ * @poll_count: (input) Number of timeouts to attempt.
+ * @poll_interval_ms: (input) Time between mailbox background command polling
+ * interval timeouts.
* @return_code: (output) Error code returned from hardware.
*
* This is the primary mechanism used to send commands to the hardware.
@@ -123,6 +127,8 @@ struct cxl_mbox_cmd {
size_t size_in;
size_t size_out;
size_t min_out;
+ int poll_count;
+ int poll_interval_ms;
u16 return_code;
};
@@ -331,6 +337,7 @@ struct cxl_dev_state {
struct cxl_event_state event;
struct cxl_poison_state poison;
+ struct rcuwait mbox_wait;
int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
};
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 18b8f3ce680c..a78e40e6d0e0 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -105,6 +105,26 @@ static int cxl_request_irq(struct cxl_dev_state *cxlds, int irq,
NULL, dev_id);
}
+static bool cxl_mbox_background_complete(struct cxl_dev_state *cxlds)
+{
+ u64 reg;
+
+ reg = readq(cxlds->regs.mbox + CXLDEV_MBOX_BG_CMD_STATUS_OFFSET);
+ return FIELD_GET(CXLDEV_MBOX_BG_CMD_COMMAND_PCT_MASK, reg) == 100;
+}
+
+static irqreturn_t cxl_pci_mbox_irq(int irq, void *id)
+{
+ struct cxl_dev_id *dev_id = id;
+ struct cxl_dev_state *cxlds = dev_id->cxlds;
+
+ /* short-circuit the wait in __cxl_pci_mbox_send_cmd() */
+ if (cxl_mbox_background_complete(cxlds))
+ rcuwait_wake_up(&cxlds->mbox_wait);
+
+ return IRQ_HANDLED;
+}
+
/**
* __cxl_pci_mbox_send_cmd() - Execute a mailbox command
* @cxlds: The device state to communicate with.
@@ -198,6 +218,50 @@ static int __cxl_pci_mbox_send_cmd(struct cxl_dev_state *cxlds,
mbox_cmd->return_code =
FIELD_GET(CXLDEV_MBOX_STATUS_RET_CODE_MASK, status_reg);
+ /*
+ * Handle the background command in a synchronous manner.
+ *
+ * All other mailbox commands will serialize/queue on the mbox_mutex,
+ * which we currently hold. Furthermore this also guarantees that
+ * cxl_mbox_background_complete() checks are safe amongst each other,
+ * in that no new bg operation can occur in between.
+ *
+ * Background operations are timesliced in accordance with the nature
+ * of the command. In the event of timeout, the mailbox state is
+ * indeterminate until the next successful command submission and the
+ * driver can get back in sync with the hardware state.
+ */
+ if (mbox_cmd->return_code == CXL_MBOX_CMD_RC_BACKGROUND) {
+ u64 bg_status_reg;
+ int i, timeout = mbox_cmd->poll_interval_ms;
+
+ dev_dbg(dev, "Mailbox background operation (0x%04x) started\n",
+ mbox_cmd->opcode);
+
+ for (i = 0; i < mbox_cmd->poll_count; i++) {
+ if (rcuwait_wait_event_timeout(&cxlds->mbox_wait,
+ cxl_mbox_background_complete(cxlds),
+ TASK_UNINTERRUPTIBLE,
+ msecs_to_jiffies(timeout)) > 0)
+ break;
+ }
+
+ if (!cxl_mbox_background_complete(cxlds)) {
+ dev_err(dev, "timeout waiting for background (%d ms)\n",
+ timeout * mbox_cmd->poll_count);
+ return -ETIMEDOUT;
+ }
+
+ bg_status_reg = readq(cxlds->regs.mbox +
+ CXLDEV_MBOX_BG_CMD_STATUS_OFFSET);
+ mbox_cmd->return_code =
+ FIELD_GET(CXLDEV_MBOX_BG_CMD_COMMAND_RC_MASK,
+ bg_status_reg);
+ dev_dbg(dev,
+ "Mailbox background operation (0x%04x) completed\n",
+ mbox_cmd->opcode);
+ }
+
if (mbox_cmd->return_code != CXL_MBOX_CMD_RC_SUCCESS) {
dev_dbg(dev, "Mailbox operation had an error: %s\n",
cxl_mbox_cmd_rc2str(mbox_cmd));
@@ -292,6 +356,31 @@ static int cxl_pci_setup_mailbox(struct cxl_dev_state *cxlds)
dev_dbg(cxlds->dev, "Mailbox payload sized %zu",
cxlds->payload_size);
+ rcuwait_init(&cxlds->mbox_wait);
+
+ if (cap & CXLDEV_MBOX_CAP_BG_CMD_IRQ) {
+ u32 ctrl;
+ int irq, msgnum;
+ struct pci_dev *pdev = to_pci_dev(cxlds->dev);
+
+ msgnum = FIELD_GET(CXLDEV_MBOX_CAP_IRQ_MSGNUM_MASK, cap);
+ irq = pci_irq_vector(pdev, msgnum);
+ if (irq < 0)
+ goto mbox_poll;
+
+ if (cxl_request_irq(cxlds, irq, cxl_pci_mbox_irq, NULL))
+ goto mbox_poll;
+
+ /* enable background command mbox irq support */
+ ctrl = readl(cxlds->regs.mbox + CXLDEV_MBOX_CTRL_OFFSET);
+ ctrl |= CXLDEV_MBOX_CTRL_BG_CMD_IRQ;
+ writel(ctrl, cxlds->regs.mbox + CXLDEV_MBOX_CTRL_OFFSET);
+
+ return 0;
+ }
+
+mbox_poll:
+ dev_dbg(cxlds->dev, "Mailbox interrupts are unsupported");
return 0;
}
--
2.40.1
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