Re: [PATCH v1] serial: qcom_geni: Fix RX DMA stall when SE_DMA_RX_LEN_IN is zero

[Bartosz Golaszewski]

On Thu, 28 May 2026 09:05:43 +0200, Viken Dadhaniya
<viken.dadhaniya@xxxxxxxxxxxxxxxx> said:
> 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")
> Signed-off-by: Viken Dadhaniya <viken.dadhaniya@xxxxxxxxxxxxxxxx>
> ---

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>