[PATCH v2 3/7] serial: qcom-geni: fix dma rx cancellation

[Johan Hovold <johan+linaro@kernel.org>]

Make sure to wait for the DMA transfer to complete when cancelling the
rx command on stop_rx(). This specifically prevents the DMA completion
interrupt from firing after rx has been restarted, something which can
lead to an IOMMU fault and hosed rx when the interrupt handler unmaps
the DMA buffer for the new command:

	qcom_geni_serial 988000.serial: serial engine reports 0 RX bytes in!
	arm-smmu 15000000.iommu: FSR    = 00000402 [Format=2 TF], SID=0x563
	arm-smmu 15000000.iommu: FSYNR0 = 00210013 [S1CBNDX=33 WNR PLVL=3]
	Bluetooth: hci0: command 0xfc00 tx timeout
	Bluetooth: hci0: Reading QCA version information failed (-110)

Also add the missing state machine reset which is needed in case
cancellation fails.

Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA")
Cc: stable@vger.kernel.org      # 6.3
Cc: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index b6a8729cee6d..dea688db0d7c 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -787,17 +787,27 @@ static void qcom_geni_serial_start_rx_fifo(struct uart_port *uport)
 static void qcom_geni_serial_stop_rx_dma(struct uart_port *uport)
 {
 	struct qcom_geni_serial_port *port = to_dev_port(uport);
+	bool done;
 
 	if (!qcom_geni_serial_secondary_active(uport))
 		return;
 
 	geni_se_cancel_s_cmd(&port->se);
-	qcom_geni_serial_poll_bit(uport, SE_GENI_S_IRQ_STATUS,
-				  S_CMD_CANCEL_EN, true);
-
-	if (qcom_geni_serial_secondary_active(uport))
+	done = qcom_geni_serial_poll_bit(uport, SE_DMA_RX_IRQ_STAT,
+			RX_EOT, true);
+	if (done) {
+		writel(RX_EOT | RX_DMA_DONE,
+				uport->membase + SE_DMA_RX_IRQ_CLR);
+	} else {
 		qcom_geni_serial_abort_rx(uport);
 
+		writel(1, uport->membase + SE_DMA_RX_FSM_RST);
+		qcom_geni_serial_poll_bit(uport, SE_DMA_RX_IRQ_STAT,
+				RX_RESET_DONE, true);
+		writel(RX_RESET_DONE | RX_DMA_DONE,
+				uport->membase + SE_DMA_RX_IRQ_CLR);
+	}
+
 	if (port->rx_dma_addr) {
 		geni_se_rx_dma_unprep(&port->se, port->rx_dma_addr,
 				      DMA_RX_BUF_SIZE);
-- 
2.45.2