Re: [PATCH v2 02/12] target/hppa: Add "diag 0x101" for console output support

[Richard Henderson <richard.henderson@linaro.org>]

On 2/9/24 01:56, deller@kernel.org wrote:
> From: Helge Deller<deller@gmx.de>
> 
> For debugging purposes at the early stage of the bootup process,
> the SeaBIOS-hppa firmware sometimes needs to output characters to the
> serial console. Note that the serial console is the default output
> method for parisc machines.
> 
> At this stage PCI busses and other devices haven't been initialized
> yet. So, SeaBIOS-hppa will not be able to find the correct I/O ports
> for the serial ports yet.
> 
> Instead, add an emulation for the "diag 0x101" opcode to assist here.
> Without any other dependencies, SeaBIOS-hppa can then load the character
> to be printed in register %r26 and issue the diag assembly instruction.
> 
> The qemu diag_console_output() helper function will then print
> that character to the first serial port.
> 
> Signed-off-by: Helge Deller<deller@gmx.de>
> ---
>   target/hppa/helper.h     |  1 +
>   target/hppa/sys_helper.c | 36 ++++++++++++++++++++++++++++++++++++
>   target/hppa/translate.c  |  6 ++++++
>   3 files changed, 43 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~