Re: Regression in serial console on ia64 after 2.6.22

[Yinghai Lu <Yinghai.Lu@Sun.COM>]

Horms wrote:
> Hi,
> 
> 18a8bd949d6adb311ea816125ff65050df1f3f6e appears to have caused
> a regression in the serial console for ia64. I have observed the
> problem on Intel Tiger2 and HP RX2620 when the console or early
> cons option is specified.
> 
> For reference
> 
> Tiger2: console=uart,io,0x2f8,115200n8
> RX2620: console=uart,mmio,0xff5e0000,115200n8
> 
> uart may also be uart8250, it makes no difference with regards to
> this problem. console may be earlycons, that also makes no
> difference as 18a8bd949d6adb311ea816125ff65050df1f3f6e handles
> both options the almost the same way.
> 
> On the RX2620 a work around is to omit the console and earlycons
> parameters all together, as the code in efi_setup_pcdp_console() will
> autodetect the console and set it up correctly.
> 
> 
> I believe that the problem is as follows:
> 
> After 18a8bd949d6adb311ea816125ff65050df1f3f6e, both the console
> and earlycons options are handled by early_param, using the callback
> setup_early_serial8250_console().
> 
> On ia64, for the hardware that I am observing this problem on
> (HP RX2620 and Intel Tiger2), I believe that I am seeing the
> following calls occur.
> 
> ->arch/ia64/kernel/setup.c:setup_arch()
>  ->parse_early_param()
>   ->setup_early_serial8250_console()    N.B callback
>    ->early_serial8250_setup()
>     ->init_port()
>      ->serial_out()
>       ->outb()
>        ->__outb()
>         ->platform_outb()
>          ->ia64_mv.outb()
> 
> However, ia64_mv may not be set until after machvec_init() is called
> by setup_arch(), which occurs after the call to parse_early_param().
> 
> The reason for this ordering is that machvec_init() may be
> influenced by the machvec command line argument, which
> is also handled by early_param. A chicken an egg problem.
> 
> 
> A fairly simple work-around would be to call machvec_init earlier
> and have it parse the command like itself.
> 
> Another solution would be to split up early_serial8250_setup()
> or setup_early_serial8250_console() somehow, such that init_port()
> is not called as part of the early_param callback, but rather later
> explicitly (probably by each architecture's setup_arch()). This is
> somewhat similar to the way that machvec is handled.
> 
> I'm sure there are are other good, possibly better solutions.
> Hence this email.

how about modify boot_command_line and put machvec at the first entry. and use setup_machvec to call machvev_init.

YH