Re: [PATCH] hw/ide: Remove status register read side effect

[BALATON Zoltan]

On Fri, 21 Feb 2020, address@hidden wrote:
> The Linux libATA API documentation mentions that on some hardware,
> reading the status register has the side effect of clearing the
> interrupt condition. When emulating the generic Sun4u machine running
> Solaris 10, the Solaris 10 CMD646 driver exits fatally because of this
> emulated side effect. This side effect is likely to not exist on real
> CMD646 hardware.

The chip docs don't mention any side effect, they only say that the DMA 
IRQ and Error bits in the bus master IDE status reg (bits 2 and 1) are 
write 1 to clear so this might be OK but this change seems to break 
something else according to a CI test report from patchew. Unfortunately 
this does not change my problems with other BMDMA devices on PPC.

Regards,
BALATON Zoltan

> Signed-off-by: Jasper Lowell <address@hidden>
> ---
> hw/ide/core.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 80000eb766..82fd0632ac 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -2210,7 +2210,6 @@ uint32_t ide_ioport_read(void *opaque, uint32_t addr)
>         } else {
>             ret = s->status;
>         }
> -        qemu_irq_lower(bus->irq);
>         break;
>     }