This is a note to let you know that I've just added the patch titled
serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-8250-fall-back-to-non-dma-rx-if-iir_rdi-occurs.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a931237cbea256aff13bb403da13a97b2d1605d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Date: Tue, 8 Nov 2022 14:19:49 +0200
Subject: serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs
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From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
commit a931237cbea256aff13bb403da13a97b2d1605d9 upstream.
DW UART sometimes triggers IIR_RDI during DMA Rx when IIR_RX_TIMEOUT
should have been triggered instead. Since IIR_RDI has higher priority
than IIR_RX_TIMEOUT, this causes the Rx to hang into interrupt loop.
The problem seems to occur at least with some combinations of
small-sized transfers (I've reproduced the problem on Elkhart Lake PSE
UARTs).
If there's already an on-going Rx DMA and IIR_RDI triggers, fall
graciously back to non-DMA Rx. That is, behave as if IIR_RX_TIMEOUT had
occurred.
8250_omap already considers IIR_RDI similar to this change so its
nothing unheard of.
Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling")
Cc: <stable@xxxxxxxxxxxxxxx>
Co-developed-by: Srikanth Thokala <srikanth.thokala@xxxxxxxxx>
Signed-off-by: Srikanth Thokala <srikanth.thokala@xxxxxxxxx>
Co-developed-by: Aman Kumar <aman.kumar@xxxxxxxxx>
Signed-off-by: Aman Kumar <aman.kumar@xxxxxxxxx>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221108121952.5497-2-ilpo.jarvinen@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_port.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1885,6 +1885,10 @@ EXPORT_SYMBOL_GPL(serial8250_modem_statu
static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
{
switch (iir & 0x3f) {
+ case UART_IIR_RDI:
+ if (!up->dma->rx_running)
+ break;
+ fallthrough;
case UART_IIR_RX_TIMEOUT:
serial8250_rx_dma_flush(up);
fallthrough;
Patches currently in stable-queue which might be from ilpo.jarvinen@xxxxxxxxxxxxxxx are
queue-5.15/serial-8250-flush-dma-rx-on-rlsi.patch
queue-5.15/serial-8250_lpss-configure-dma-also-w-o-dma-filter.patch
queue-5.15/serial-8250-fall-back-to-non-dma-rx-if-iir_rdi-occurs.patch
queue-5.15/serial-8250_omap-remove-wait-loop-from-errata-i202-w.patch
