From 1a10ab746b96eec6fd82658826b344ae4e053f5a Mon Sep 17 00:00:00 2001 From: Viken Dadhaniya Date: Mon, 25 May 2026 16:12:08 +0530 Subject: [PATCH] FROMLIST: serial: qcom_geni: Fix RX DMA stall when SE_DMA_RX_LEN_IN is zero In qcom_geni_serial_handle_rx_dma(), geni_se_rx_dma_unprep() clears port->rx_dma_addr before SE_DMA_RX_LEN_IN is read. If the register is zero, for example when the RX stale counter fires on an idle line, the handler returns without calling geni_se_rx_dma_prep(). The next RX DMA interrupt then hits the !port->rx_dma_addr guard and returns immediately, so the RX DMA buffer is never rearmed and later input is lost. Keep the handler on the rearm path when rx_in is zero. Warn about the unexpected zero-length DMA completion, skip received-data handling, and always call geni_se_rx_dma_prep(). Link: https://lore.kernel.org/all/20260528-serial-rx-0-byte-fix-v1-1-dc4e876c7368@oss.qualcomm.com/ Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA") Signed-off-by: Viken Dadhaniya --- drivers/tty/serial/qcom_geni_serial.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index cbb4f3222116a..92242fa1d7859 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -896,12 +896,9 @@ static void qcom_geni_serial_handle_rx_dma(struct uart_port *uport, bool drop) port->rx_dma_addr = 0; rx_in = readl(uport->membase + SE_DMA_RX_LEN_IN); - if (!rx_in) { - dev_warn(uport->dev, "serial engine reports 0 RX bytes in!\n"); - return; - } - - if (!drop) + if (!rx_in) + dev_warn_ratelimited(uport->dev, "serial engine reports 0 RX bytes in!\n"); + else if (!drop) handle_rx_uart(uport, rx_in); ret = geni_se_rx_dma_prep(&port->se, port->rx_buf,