[PATCH v4 3/3] spi: tegra210-quad: Check hardware status on timeout

Vishwaroop A
2025-10-28T15:27:42Z

Under high system load, QSPI interrupts can be delayed or blocked on the
target CPU, causing wait_for_completion_timeout() to report failure even
though the hardware successfully completed the transfer.

When a timeout occurs, check the QSPI_RDY bit in QSPI_TRANS_STATUS to
determine if the hardware actually completed the transfer. If so, manually
invoke the completion handler to process the transfer successfully instead
of failing it.

This distinguishes lost/delayed interrupts from real hardware timeouts,
preventing unnecessary failures of transfers that completed successfully.

Signed-off-by: Vishwaroop A <va@nvidia.com>
---
drivers/spi/spi-tegra210-quad.c | 100 +++++++++++++++++++++++++-------
1 file changed, 80 insertions(+), 20 deletions(-)

diff --git a/drivers/spi/spi-tegra210-quad.c b/drivers/spi/spi-tegra210-quad.c
index 69defb4ffe49..cdc3cb7c01f9 100644
--- a/drivers/spi/spi-tegra210-quad.c
+++ b/drivers/spi/spi-tegra210-quad.c
@@ -1048,6 +1048,49 @@ static void tegra_qspi_transfer_end(struct spi_device *spi)
tegra_qspi_writel(tqspi, tqspi->def_command1_reg, QSPI_COMMAND1);
}

+static irqreturn_t handle_cpu_based_xfer(struct tegra_qspi *tqspi);
+static irqreturn_t handle_dma_based_xfer(struct tegra_qspi *tqspi);
+
+/**
+ * tegra_qspi_handle_timeout - Handle transfer timeout with hardware check
+ * @tqspi: QSPI controller instance
+ *
+ * When a timeout occurs but hardware has completed the transfer (interrupt
+ * was lost or delayed), manually trigger transfer completion processing.
+ * This avoids failing transfers that actually succeeded.
+ *
+ * Returns: 0 if transfer was completed, -ETIMEDOUT if real timeout
+ */
+static int tegra_qspi_handle_timeout(struct tegra_qspi *tqspi)
+{
+ irqreturn_t ret;
+ u32 status;
+
+ /* Check if hardware actually completed the transfer */
+ status = tegra_qspi_readl(tqspi, QSPI_TRANS_STATUS);
+ if (!(status & QSPI_RDY))
+ return -ETIMEDOUT;
+
+ /*
+ * Hardware completed but interrupt was lost/delayed. Manually
+ * process the completion by calling the appropriate handler.
+ */
+ dev_warn_ratelimited(tqspi->dev,
+ "QSPI interrupt timeout, but transfer complete\n");
+
+ /* Clear the transfer status */
+ status = tegra_qspi_readl(tqspi, QSPI_TRANS_STATUS);
+ tegra_qspi_writel(tqspi, status, QSPI_TRANS_STATUS);
+
+ /* Manually trigger completion handler */
+ if (!tqspi->is_curr_dma_xfer)
+ ret = handle_cpu_based_xfer(tqspi);
+ else
+ ret = handle_dma_based_xfer(tqspi);
+
+ return (ret == IRQ_HANDLED) ? 0 : -EIO;
+}
+
static u32 tegra_qspi_cmd_config(bool is_ddr, u8 bus_width, u8 len)
{
u32 cmd_config = 0;
@@ -1177,20 +1220,28 @@ static int tegra_qspi_combined_seq_xfer(struct tegra_qspi *tqspi,
QSPI_DMA_TIMEOUT);

if (WARN_ON_ONCE(ret == 0)) {
- dev_err_ratelimited(tqspi->dev,
- "QSPI Transfer failed with timeout\n");
-
- /* Abort transfer by resetting pio/dma bit */
- if (tqspi->is_curr_dma_xfer)
- tegra_qspi_dma_stop(tqspi);
- else
- tegra_qspi_pio_stop(tqspi);
-
- /* Reset controller if timeout happens */
- tegra_qspi_reset(tqspi);
-
- ret = -EIO;
- goto exit;
+ /*
+ * Check if hardware completed the transfer
+ * even though interrupt was lost or delayed.
+ * If so, process the completion and continue.
+ */
+ ret = tegra_qspi_handle_timeout(tqspi);
+ if (ret < 0) {
+ /* Real timeout - clean up and fail */
+ dev_err(tqspi->dev, "transfer timeout\n");
+
+ /* Abort transfer by resetting pio/dma bit */
+ if (tqspi->is_curr_dma_xfer)
+ tegra_qspi_dma_stop(tqspi);
+ else
+ tegra_qspi_pio_stop(tqspi);
+
+ /* Reset controller if timeout happens */
+ tegra_qspi_reset(tqspi);
+
+ ret = -EIO;
+ goto exit;
+ }
}

if (tqspi->tx_status || tqspi->rx_status) {
@@ -1281,14 +1332,23 @@ static int tegra_qspi_non_combined_seq_xfer(struct tegra_qspi *tqspi,
ret = wait_for_completion_timeout(&tqspi->xfer_completion,
QSPI_DMA_TIMEOUT);
if (WARN_ON(ret == 0)) {
- dev_err(tqspi->dev, "transfer timeout\n");
+ /*
+ * Check if hardware completed the transfer even though
+ * interrupt was lost or delayed. If so, process the
+ * completion and continue.
+ */
+ ret = tegra_qspi_handle_timeout(tqspi);
+ if (ret < 0) {
+ /* Real timeout - clean up and fail */
+ dev_err(tqspi->dev, "transfer timeout\n");

- if (tqspi->is_curr_dma_xfer)
- tegra_qspi_dma_stop(tqspi);
+ if (tqspi->is_curr_dma_xfer)
+ tegra_qspi_dma_stop(tqspi);

- tegra_qspi_handle_error(tqspi);
- ret = -EIO;
- goto complete_xfer;
+ tegra_qspi_handle_error(tqspi);
+ ret = -EIO;
+ goto complete_xfer;
+ }
}

if (tqspi->tx_status || tqspi->rx_status) {
--
2.17.1