On 09/04/2026 15:50, Oleksii Moisieiev wrote:
> In scif_uart_init_postirq(), when setup_irq() returns an error the
> failure was only logged via dprintk() and execution continued,
> unconditionally writing TIE|RIE|REIE into the Serial Control Register
> (SCSCR). This armed all three hardware interrupt lines (TX FIFO empty,
> RX data ready, receive error) with no handler registered to service
> them. On platforms where the GIC receives these asserted lines, the
> result is either repeated spurious-interrupt warnings or an unhandled
> interrupt fault.
>
> The fix adds an early return inside the error branch. The
> interrupt-enable write to SCSCR is skipped entirely when no handler is
> registered.
>
> SCIF TX continues to operate correctly after this change. The Xen
> serial framework never calls serial_async_transmit() for SCIF, so
> port->txbuf is always NULL. This causes __serial_putc() to take the
> synchronous finite-capacity path, which polls the SCFSR_TDFE hardware
> flag directly and does not depend on the interrupt mechanism. RX
> wouldn't work if irq wasn't registered.
>
> As a secondary clean-up, the hardware error-flag clearing sequence is
> moved to before the setup_irq() call so that error bits accumulated
> since init_preirq() are cleared unconditionally, regardless of whether
> IRQ registration succeeds.
>
> Signed-off-by: Oleksii Moisieiev <[email protected]>
Reviewed-by: Michal Orzel <[email protected]>
~Michal
