rivers: scmi: Add completion timeout handling for raw mode transfers

Fix race conditions in SCMI raw mode implementation by adding proper completion timeout handling. Multiple tests in the SCMI test suite were failing due to early clearing of SCMI_XFER_FLAG_IS_RAW flag in scmi_xfer_raw_put() function.

The root cause:
Tests were failing on poll() system calls with this condition:

    if (!raw || (idx == SCMI_RAW_REPLY_QUEUE && !SCMI_XFER_IS_RAW(xfer)))
        return;

The SCMI_XFER_FLAG_IS_RAW flag was being cleared prematurely before the transfer completion was properly acknowledged, causing the poll to return on timeout and tests to fail.

Сhanges implemented:
1. Add completion wait with timeout in scmi_xfer_raw_worker()
2. Signal completion in scmi_raw_message_report()

This ensures:
- Proper synchronization between transfer completion and flag clearing
- Prevention of indefinite blocking with timeout safety mechanism
- Stable test execution by maintaining correct flag states

arm scmi tests: https://gitlab.arm.com/tests/scmi-tests/-/releases

Signed-off-by Artem Shimko <[email protected]>

---
 drivers/firmware/arm_scmi/raw_mode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

drivers/firmware/arm_scmi/raw_mode.c +8 -1

index 73db5492ab44..fb83beb42e7b 100644
@@ -468,6 +468,12 @@ static void scmi_xfer_raw_worker(struct work_struct *work)
 
                ret = scmi_xfer_raw_wait_for_message_response(cinfo, xfer,
                                                              timeout_ms);
+               if (!ret)
+                       if (!wait_for_completion_timeout(&xfer->done, timeout_ms))
+                               dev_err(dev,
+                                       "timed out in RAW resp - HDR:%08X\n",
+                                       pack_scmi_header(&xfer->hdr));
+
                if (!ret && xfer->hdr.status)
                        ret = scmi_to_linux_errno(xfer->hdr.status);
 

@@ -1381,6 +1387,8 @@ void scmi_raw_message_report(void *r, struct scmi_xfer *xfer,
        if (!raw || (idx == SCMI_RAW_REPLY_QUEUE && !SCMI_XFER_IS_RAW(xfer)))
                return;
 
+       complete(&xfer->done);
+
        dev = raw->handle->dev;
        q = scmi_raw_queue_select(raw, idx,
                                  SCMI_XFER_IS_CHAN_SET(xfer) ? chan_id : 0);
--

2.43.0