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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 21 Jul 2015 14:02:49 +0100
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Subject: Re: [Qemu-devel] [PULL 2/3] ahci: Force ICC bits in PxCMD to zero
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To: Eric Blake <eblake@redhat.com>
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On 21 July 2015 at 13:55, Eric Blake <eblake@redhat.com> wrote:
> On 07/21/2015 05:38 AM, Peter Maydell wrote:
>> On 20 July 2015 at 19:29, John Snow <jsnow@redhat.com> wrote:
>>> From: Stefan Fritsch <sf@sfritsch.de>
>>>
>>> The AHCI spec requires that the HBA sets the ICC bits to zero after the
>>> ICC change is done. Since we don't do any ICC change, force the bits to
>>> zero all the time.
>>>
>>> This fixes delays with some OSs (e.g. OpenBSD) waiting for the ICC bits
>>> to change to 0.
>>
>> This change provokes a lot of clang sanitizer warnings:
>>
>> /home/petmay01/linaro/qemu-for-merges/hw/ide/ahci.c:288:49: runtime
>> error: left shift of 15 by 28 places cannot be represented in type
>> 'int'
>>
>> PORT_CMD_ICC_MASK is defined as
>>
>>  #define PORT_CMD_ICC_MASK         (0xf << 28) /* i/f ICC state mask */
>>
>> which shifts into the sign bit of a signed integer.
>
> Should be fixable by using (0xfU << 28), right?

Yes, though it assumes that if you say "~PORT_CMD_ICC_MASK"
you're happy to only get a 32-bit mask. 0xfULL would avoid
that (see discussion on the other thread with Paolo about
the PPC similar issue.)

-- PMM