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Re: OSSynchronizeIO and device memory
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Re: OSSynchronizeIO and device memory

Shawn,

Thank you for the response.

We are not using a DMA engine, that's part of the problem.

And the "order" is not really important in this case. I mean a read does
not really depend on a previous write having gone through! I mean the
previous writes that do matter are all under "my" control, and I can put
the proper OSSyncIO in the correct places.

I was only worried about the write not making all the way out to the
device (a cache issue?).

It looks like I have no reason to worry now!

Thanks.

Devendra.

At 09:58 AM 10/26/2002, Shawn Erickson wrote:

On Thursday, October 24, 2002, at 10:32 AM, Devendra Parakh wrote:

> Hi,
>
> We have a PCI card(audio) which has a large buffer that we use to
> transfer data.
>
> If I understand correctly, before reading from device memory, and
after
> writing to device memory, I need to call OSSynchronizeIO.
>
> Is there a way to avoid this?

Are you using a DMA engine to move things? If you are then you don't
need t worry about OSSynchronizeIO.

You only really need OSSynchronizeIO between memory operations that
have to happen in a specific order. For example writing bits into a
mailbox registers followed by setting a bit to get your adapter to do
something with the data you wrote in the mailbox. You want the IO ops
related to the mailbox registers to happen before the trigger bit, to
do this insert OSSynchronizeIO between the first block of writes and
the final write.

Example... (WL16 is a macro for writing out 16 bit value byte swapped
as needed)

if ( BIT_TEST( mask, MB_BOX0 ) ) WL16( m_box0, box[0] );
if ( BIT_TEST( mask, MB_BOX1 ) ) WL16( m_box1, box[1] );
if ( BIT_TEST( mask, MB_BOX2 ) ) WL16( m_box2, box[2] );
if ( BIT_TEST( mask, MB_BOX3 ) ) WL16( m_box3, box[3] );
if ( BIT_TEST( mask, MB_BOX4 ) ) WL16( m_box4, box[4] );
if ( BIT_TEST( mask, MB_BOX5 ) ) WL16( m_box5, box[5] );
if ( BIT_TEST( mask, MB_BOX6 ) ) WL16( m_box6, box[6] );
if ( BIT_TEST( mask, MB_BOX7 ) ) WL16( m_box7, box[7] );
OSSynchronizeIO();
WL16( &m_isp->hccr, FIELD_INSERT( 0, HCCR_COMMAND,
HCCR_COMMAND_SET_HOST_INT ) );

Or...
WL16( &m_isp->intctl, tmpIntctl );
OSSynchronizeIO();
for ( unsigned int i = 0; i < 500; i++ )
{
if ( RL16( &m_isp->intctl ) == tmpIntctl )
{
bIntSetComplete = true;
break;
}
....
}

-Shawn
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Devendra ParakhSinging Electrons, Inc.http://www.singingelectrons.com425-889-2478
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References: 
 >Re: OSSynchronizeIO and device memory (From: Shawn Erickson <email@hidden>)



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