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Date: Wed, 29 Oct 2014 09:11:22 +0100
From: Hannes Reinecke <hare@suse.de>
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Subject: Re: [Qemu-devel] [PATCH 01/17] ahci: Fix CD-ROM signature
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To: Markus Armbruster <armbru@redhat.com>
Cc: Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org, Nic Bellinger <nab@datera.com>, Paolo Bonzini <pbonzini@redhat.com>, John Snow <jsnow@redhat.com>, Andreas Faerber <afaerber@suse.de>

On 10/29/2014 09:07 AM, Markus Armbruster wrote:
> Copying John Snow for additional AHCI expertise.
>=20
> Hannes Reinecke <hare@suse.de> writes:
>=20
>> The CD-ROM signature is 0xeb140101, not 0xeb140000.
>> Without this change OVMF/Duet runs into a timeout trying
>> to detect a SATA cdrom.
>>
>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>> ---
>>  hw/ide/ahci.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/ide/ahci.h b/hw/ide/ahci.h
>> index e223258..970eea8 100644
>> --- a/hw/ide/ahci.h
>> +++ b/hw/ide/ahci.h
>> @@ -161,7 +161,7 @@
>>  #define AHCI_CMD_HDR_CMD_FIS_LEN           0x1f
>>  #define AHCI_CMD_HDR_PRDT_LEN              16
>> =20
>> -#define SATA_SIGNATURE_CDROM               0xeb140000
>> +#define SATA_SIGNATURE_CDROM               0xeb140101
>>  #define SATA_SIGNATURE_DISK                0x00000101
>> =20
>>  #define AHCI_GENERIC_HOST_CONTROL_REGS_MAX_ADDR 0x20

This is actually required by DUET/OVMF.
It just does this check:

(sig & 0xFFFF) =3D=3D 0x0101

and hence will run into a timeout when a CDROM is attached
to ahci.
It's even in the ATA spec ...

Cheers,

Hannes
--=20
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg
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