[PATCH v2 1/2] hwtracing: hisi_ptt: Propagate DMA reset timeout in trace_start()

["Pradhan, Sanman" <sanman.pradhan@hpe.com>]

From: Sanman Pradhan <psanman@juniper.net>

hisi_ptt_wait_dma_reset_done() discards the return value of
readl_poll_timeout_atomic(). If the DMA engine does not complete its
reset within the timeout, hisi_ptt_trace_start() proceeds to start
tracing regardless.

Return a bool from hisi_ptt_wait_dma_reset_done(), consistent with the
other wait helpers in this driver. On timeout, log an error, de-assert
the reset bit, and return -ETIMEDOUT. Move ctrl->started to the
successful path so a failed start does not leave the trace marked as
active.

Fixes: ff0de066b463 ("hwtracing: hisi_ptt: Add trace function support for HiSilicon PCIe Tune and Trace device")
Cc: stable@vger.kernel.org
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
---
v2:
  - Return bool for consistency with other wait helpers
  - Add pci_err() on timeout
  - De-assert RST before returning on timeout
  - Move ctrl->started to the successful path

 drivers/hwtracing/ptt/hisi_ptt.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
index 94c371c491357..b5d851281fbf0 100644
--- a/drivers/hwtracing/ptt/hisi_ptt.c
+++ b/drivers/hwtracing/ptt/hisi_ptt.c
@@ -171,13 +171,13 @@ static bool hisi_ptt_wait_trace_hw_idle(struct hisi_ptt *hisi_ptt)
 					  HISI_PTT_WAIT_TRACE_TIMEOUT_US);
 }
 
-static void hisi_ptt_wait_dma_reset_done(struct hisi_ptt *hisi_ptt)
+static bool hisi_ptt_wait_dma_reset_done(struct hisi_ptt *hisi_ptt)
 {
 	u32 val;
 
-	readl_poll_timeout_atomic(hisi_ptt->iobase + HISI_PTT_TRACE_WR_STS,
-				  val, !val, HISI_PTT_RESET_POLL_INTERVAL_US,
-				  HISI_PTT_RESET_TIMEOUT_US);
+	return !readl_poll_timeout_atomic(hisi_ptt->iobase + HISI_PTT_TRACE_WR_STS,
+					  val, !val, HISI_PTT_RESET_POLL_INTERVAL_US,
+					  HISI_PTT_RESET_TIMEOUT_US);
 }
 
 static void hisi_ptt_trace_end(struct hisi_ptt *hisi_ptt)
@@ -202,14 +202,18 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
 		return -EBUSY;
 	}
 
-	ctrl->started = true;
-
 	/* Reset the DMA before start tracing */
 	val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
 	val |= HISI_PTT_TRACE_CTRL_RST;
 	writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
 
-	hisi_ptt_wait_dma_reset_done(hisi_ptt);
+	if (!hisi_ptt_wait_dma_reset_done(hisi_ptt)) {
+		pci_err(hisi_ptt->pdev, "timed out waiting for DMA reset\n");
+		val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
+		val &= ~HISI_PTT_TRACE_CTRL_RST;
+		writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
+		return -ETIMEDOUT;
+	}
 
 	val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
 	val &= ~HISI_PTT_TRACE_CTRL_RST;
@@ -234,6 +238,8 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
 	if (!hisi_ptt->trace_ctrl.is_port)
 		val |= HISI_PTT_TRACE_CTRL_FILTER_MODE;
 
+	ctrl->started = true;
+
 	/* Start the Trace */
 	val |= HISI_PTT_TRACE_CTRL_EN;
 	writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
-- 
2.34.1