[RFC PATCH 2/4] cxl: Add default timeout for bg mailbox commands

[Ravis OpenSrc <Ravis.OpenSrc@micron.com>]

Allows 5s wait when no timeout parameter is explicitly mentioned.

It is useful for mailbox commands to be executed in background
when initiated from userspace.

Link:
https://lore.kernel.org/linux-mm/20240215123410.00003b8c@Huawei.com/T/

Signed-off-by: Ravi Shankar <ravis.opensrc@micron.com>
---
 drivers/cxl/pci.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 188412d45e0d..d5d6142f6aa3 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -41,6 +41,10 @@
 /* CXL 2.0 - 8.2.8.4 */
 #define CXL_MAILBOX_TIMEOUT_MS (2 * HZ)
 
+/* Default timeout for background operations */
+#define CXL_BG_POLL_CNT                        5
+#define CXL_BG_POLL_INTERVAL_MS                1000
+
 /*
  * CXL 2.0 ECN "Add Mailbox Ready Time" defines a capability field to
  * dictate how long to wait for the mailbox to become ready. The new
@@ -317,6 +321,15 @@ static int __cxl_pci_mbox_send_cmd(struct cxl_mailbox *cxl_mbox,
                 dev_dbg(dev, "Mailbox background operation (0x%04x) started\n",
                         mbox_cmd->opcode);
 
+               /*
+                * Add a default timeout of 5 seconds when background operation
+                * starts but no timeout is specified.
+                */
+               if (!mbox_cmd->poll_interval_ms) {
+                       mbox_cmd->poll_interval_ms = CXL_BG_POLL_INTERVAL_MS;
+                       mbox_cmd->poll_count = CXL_BG_POLL_CNT;
+               }
+
                 timeout = mbox_cmd->poll_interval_ms;
                 for (i = 0; i < mbox_cmd->poll_count; i++) {
                         if (rcuwait_wait_event_timeout(&cxl_mbox->mbox_wait,
-- 
2.43.0