Re: [kvm-unit-tests PATCH 2/7] lib: arm: Remove warning about uart0_base mismatch

[Andrew Jones <drjones@redhat.com>]

On Thu, Jan 24, 2019 at 11:59:43AM +0000, Andre Przywara wrote:
> On Thu, 24 Jan 2019 11:16:29 +0000
> Alexandru Elisei <alexandru.elisei@arm.com> wrote:
> 
> > A warning is displayed if uart0_base is different from what the code
> > expects qemu to generate for the pl011 UART in the device tree.
> > However, now we support the ns16550a UART emulated by kvmtool, which
> > has a different address. This leads to the  warning being displayed
> > even though the UART is configured and working as expected.
> > 
> > Now that we support multiple UARTs, the warning serves no purpose, so
> > remove it.
> 
> Mmh, but we use that address before, right? So for anything not
> emulating an UART at this QEMU specific address we write to some random
> (device) memory?
> 
> Drew, how important is this early print feature for kvm-unit-tests?

The setup code passes through quite a few asserts before getting through
io_init() (including in uart0_init), so I think there's still value in
having a guessed UART address. Maybe we can provide guesses for both
QEMU and kvmtool, and some selection method, that would be used until
we've properly assigned uart0_base from DT?

> 
> Cheers,
> Andre.
> 
> > 
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> > ---
> >  lib/arm/io.c | 6 ------
> >  1 file changed, 6 deletions(-)
> > 
> > diff --git a/lib/arm/io.c b/lib/arm/io.c
> > index 35fc05aeb4db..87435150f73e 100644
> > --- a/lib/arm/io.c
> > +++ b/lib/arm/io.c
> > @@ -61,12 +61,6 @@ static void uart0_init(void)
> >  	}
> >  
> >  	uart0_base = ioremap(base.addr, base.size);
> > -
> > -	if (uart0_base != (u8 *)UART_EARLY_BASE) {
> > -		printf("WARNING: early print support may not work. "
> > -		       "Found uart at %p, but early base is %p.\n",
> > -			uart0_base, (u8 *)UART_EARLY_BASE);
> > -	}
> >  }

This warning is doing what it should, which is pointing out that the
UART_EARLY_BASE guess appears to be wrong. If we can provide a way
to support more than one guess, then we should keep this warning but
adjust it to match one of any of the guesses.

Thanks,
drew