serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs
commit a931237c 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: 75df022b ("serial: 8250_dma: Fix RX handling") Cc: <stable@vger.kernel.org> Co-developed-by:Srikanth Thokala <srikanth.thokala@intel.com> Signed-off-by:
Srikanth Thokala <srikanth.thokala@intel.com> Co-developed-by:
Aman Kumar <aman.kumar@intel.com> Signed-off-by:
Aman Kumar <aman.kumar@intel.com> Signed-off-by:
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Reviewed-by:
Andy Shevchenko <andriy.shevchenko@linux.intel.com> Link: https://lore.kernel.org/r/20221108121952.5497-2-ilpo.jarvinen@linux.intel.com Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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