Re: [Qemu-devel] [PATCH] Floppy: Remove Sense Interrupt Hack

[Blue Swirl]

On 12/23/08, Justin Chevrier <address@hidden> wrote:
> --- On Sat, 12/20/08, Blue Swirl <address@hidden> wrote:
>
>  > From: Blue Swirl <address@hidden>
>  > Subject: Re: [Qemu-devel] [PATCH] Floppy: Remove Sense Interrupt Hack
>  > To: address@hidden
>
> > Cc: address@hidden
>  > Date: Saturday, December 20, 2008, 5:54 AM
>
> > On 12/19/08, Justin Chevrier <address@hidden>
>  > wrote:
>  > >
>  > >
>  > >
>  > >  --- On Fri, 12/19/08, Blue Swirl
>  > <address@hidden> wrote:
>  > >
>  > >  > From: Blue Swirl <address@hidden>
>  > >  > Subject: Re: [Qemu-devel] [PATCH] Floppy: Remove
>  > Sense Interrupt Hack
>  > >  > To: address@hidden, address@hidden
>  > >  > Date: Friday, December 19, 2008, 2:43 PM
>  > >
>  > > > On 12/18/08, Justin Chevrier
>  > <address@hidden>
>  > >  > wrote:
>  > >  > > Hey guys,
>  > >  > >
>  > >  > >  I'm tracking down the next issue(s)
>  > with the
>  > >  > Openserver installation. The current issue is
>  > that during
>  > >  > installation when the installer tries to link
>  > the BLTD (eg.
>  > >  > SCSI drivers) drivers into the kernel it is
>  > unable to access
>  > >  > the floppy drive. After reviewing the debug logs
>  > it turns
>  > >  > out that the installer dosen't like the
>  > value being
>  > >  > returned by Sense Interrupt. The cause of this
>  > is a hack in
>  > >  > the Sense Interrupt code that always returns an
>  > OR'd
>  > >  > value based on FD_SR0_SEEK instead of the actual
>  > Status0
>  > >  > regsiter. The hack identifies that the floppy
>  > code is broken
>  > >  > with regard to Status0 and Read/Writes. Outside
>  > of setting
>  > >  > particular values in case of CRC errors/etc I
>  > can't
>  > >  > identify from datasheets what we should be
>  > doing. I've
>  > >  > tracked down what I believe is the original
>  > mailing list
>  > >  > post regarding this hack and it seems to be
>  > related to
>  > >  > Windows 2000 and higher OS's recognizing the
>  > floppy
>  > >  > drive. I applied the patch below and verified
>  > that
>  > >  > >   detection/read/writes/formatting still
>  > work in
>  > >  > Windows XP SP2.
>  > >  > >
>  > >  > >  Original post:
>  > >  > >
>  > >  >
>  > http://lists.gnu.org/archive/html/qemu-devel/2004-10/msg00076.html
>  > >  > >
>  > >  > >  SVN change:
>  > >  > >
>  > >  >
>  > http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=1118
>  > >  > >
>  > >  > >  Having said the above does anyone know
>  > what the
>  > >  > comment in the hack is referencing? Is it still
>  > needed? If
>  > >  > so what needs to be done to eliminate it?
>  > >  > >
>  > >  > >  If it's no longer needed I propose the
>  > patch
>  > >  > below.
>  > >  > >
>  > >  > >  Justin
>  > >  > >
>  > >  > >  Changelog:
>  > >  > >
>  > >  > >  Remove Sense Interrupt hack
>  > >  > >
>  > >  > >  Signed-off-by: Justin Chevrier
>  > >  > <address@hidden>
>  > >  >
>  > >  > It may be a hack, but if we remove it, Sparc64
>  > refuses to
>  > >  > boot and
>  > >  > prints endlessly:
>  > >  > SENSEI c0 00
>  > >  > SENSEI c0 00
>  > >  > SENSEI c0 00
>  > >  > SENSEI c0 00
>  > >
>  > >
>  > > Okay, thanks for the feedback!
>  > >
>  > >  I'll start looking into what SPARC64 expects
>  > here.
>  >
>  > The message is printed here:
>  > 
> http://tracker.coreboot.org/trac/openbios/browser/openbios-devel/drivers/floppy.c#L359
>
>
> Thanks again!
>
>  Does the patch below work for you?
>
>  In this version we return 0xc0 (polling) for the first interrupt status 
> after reset (Openserver appears to require this). After returning 0xc0 we set 
> the Status0 register to 0x20 (seek complete). This should work as the spec 
> says Sense Interrupt should be called up to 4 times to retrieve the queued 
> status values. Tested successfully in both Windows 98 and XP SP2.

Yes, now it also works on Sparc64:

floppy_motor_off
SENSEI c0 00
SENSEI 20 00
status = 80, reply_buffer= 20 0

>
>  It also appears that the code referenced in the link loops infinitely due to 
> a missing: "max_sensei--;" which is present in the Linux Kernel's equivalent 
> code.

Thanks, I'll try that.