From: Viken Dadhaniya Date: Thu, 28 May 2026 17:18:07 +0000 (+0530) Subject: serial: qcom_geni: Fix RX DMA stall when SE_DMA_RX_LEN_IN is zero X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b93062b6d8a1b2d9bad235cac25558a909819026;p=thirdparty%2Flinux.git 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(). Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA") Cc: stable@vger.kernel.org Reviewed-by: Bartosz Golaszewski Signed-off-by: Viken Dadhaniya Link: https://patch.msgid.link/20260528-serial-rx-0-byte-fix-v2-1-b4195cfe342f@oss.qualcomm.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index d81b539cff7f0..7ead87b4eb65b 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -905,12 +905,9 @@ 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,