Re: [Qemu-devel] [PATCH QEMU] hw/char/sh_serial: Add timeout handling to unbreak serial input

[Ulrich Hecht]

> On July 30, 2018 at 3:02 PM Geert Uytterhoeven <address@hidden> wrote:
> 
> 
> As of commit 18e8cf159177100e ("serial: sh-sci: increase RX FIFO trigger
> defaults for (H)SCIF") in Linux v4.11-rc1, the serial console on the
> QEMU SH4 target is broken: it delays serial input until enough data has
> been received.
> 
> Since aformentioned commit, the Linux SCIF driver programs the Receive
> FIFO Data Count Trigger bits in the FIFO Control Register, to postpone
> generating a receive interrupt until:
>   1. At least the receive trigger count of bytes of data are available
>      in the receive FIFO, OR
>   2. No further data has been received for at least 15 etu after the
>      last received data.
> 
> While QEMU implements the former, it does not implement the latter.
> Hence the receive interrupt is not generated until the former condition
> is met.
> 
> Fix this by adding basic timeout handling.  As the QEMU SCIF emulation
> ignores any serial speed programming, the timeout value used conforms to
> a default speed of 9600 bps, which is fine for any interative console.
> 
> Reported-by: Rob Landley <address@hidden>
> Signed-off-by: Geert Uytterhoeven <address@hidden>

Works for me, kernel 4.18-rc7 for rts7751r2dplus.

Tested-by: Ulrich Hecht <address@hidden>

CU
Uli