Megaraid: Use of outb_p

Megaraid: Use of outb_p

[Alan Cox]

I notice the MegaRAID driver uses outb_p. Can someone at LSI confirm that
the delays between each I/O are required, and if so how long they must be.

I'm trying to sort out the use of in/outb_p and where it is unneccessary
or used for non ISA devices.

(Please cc me on the reply)
Alan

RE: Megaraid: Use of outb_p

[Yang, Bo]

Alan, 

The in/outb_p in MegaRAID scsi driver is used for our old io mapped
megaraid controller.  There are still some customers are using those old
controller.  Please keep them.
 
Thanks.
 
Bo Yang  

-----Original Message-----
From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk]
Sent: Friday, January 18, 2008 7:36 AM
To: linux-scsi@vger.kernel.org; DL-MegaRAID Linux
Subject: Megaraid: Use of outb_p


I notice the MegaRAID driver uses outb_p. Can someone at LSI confirm
that the delays between each I/O are required, and if so how long they
must be.

I'm trying to sort out the use of in/outb_p and where it is unneccessary
or used for non ISA devices.

(Please cc me on the reply)
Alan

Re: Megaraid: Use of outb_p

[Alan Cox]

On Fri, 18 Jan 2008 13:32:12 -0700
"Yang, Bo" <Bo.Yang@lsi.com> wrote:

> Alan, 
> 
> The in/outb_p in MegaRAID scsi driver is used for our old io mapped
> megaraid controller.  There are still some customers are using those old
> controller.  Please keep them.

Do they need the I/O delays. If they need a delay they should use outb
and a udelay() of the correct length. If they do not need a delay they
should use outb()

Which is the correct change to make ?

Alan

Re: Megaraid: Use of outb_p

[Matthew Wilcox]

On Fri, Jan 18, 2008 at 01:32:12PM -0700, Yang, Bo wrote:
> Alan, 
> 
> The in/outb_p in MegaRAID scsi driver is used for our old io mapped
> megaraid controller.  There are still some customers are using those old
> controller.  Please keep them.

Hi Bo,

I think you've misunderstood the question.  The '_p' versions of
inb/outb introduce a delay after each access.  The current Linux
implementation of _p provokes bugs on some chipsets, so Alan is looking
for alternatives.  Let's ask the question like this:

Replacing outb_p() with outb(); udelay(x);
How large does 'x' need to be for these megaraid controllers?

> Thanks.
>  
> Bo Yang  
> 
> -----Original Message-----
> From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk]
> Sent: Friday, January 18, 2008 7:36 AM
> To: linux-scsi@vger.kernel.org; DL-MegaRAID Linux
> Subject: Megaraid: Use of outb_p
> 
> 
> I notice the MegaRAID driver uses outb_p. Can someone at LSI confirm
> that the delays between each I/O are required, and if so how long they
> must be.
> 
> I'm trying to sort out the use of in/outb_p and where it is unneccessary
> or used for non ISA devices.
> 
> (Please cc me on the reply)
> Alan
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

RE: Megaraid: Use of outb_p

[Yang, Bo]

Alan/Matthew,

I found inb_p/outb_p are defined as inb/outb in kernel src.  So it
should not have problems to change inb_p/outb_p to inb/outb.

Thanks.

Bo Yang 


-----Original Message-----
From: Matthew Wilcox [mailto:matthew@wil.cx] 
Sent: Friday, January 18, 2008 3:41 PM
To: Yang, Bo
Cc: Alan Cox; linux-scsi@vger.kernel.org; DL-MegaRAID Linux
Subject: Re: Megaraid: Use of outb_p

On Fri, Jan 18, 2008 at 01:32:12PM -0700, Yang, Bo wrote:
> Alan,
> 
> The in/outb_p in MegaRAID scsi driver is used for our old io mapped 
> megaraid controller.  There are still some customers are using those 
> old controller.  Please keep them.

Hi Bo,

I think you've misunderstood the question.  The '_p' versions of
inb/outb introduce a delay after each access.  The current Linux
implementation of _p provokes bugs on some chipsets, so Alan is looking
for alternatives.  Let's ask the question like this:

Replacing outb_p() with outb(); udelay(x); How large does 'x' need to be
for these megaraid controllers?

> Thanks.
>  
> Bo Yang
> 
> -----Original Message-----
> From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk]
> Sent: Friday, January 18, 2008 7:36 AM
> To: linux-scsi@vger.kernel.org; DL-MegaRAID Linux
> Subject: Megaraid: Use of outb_p
> 
> 
> I notice the MegaRAID driver uses outb_p. Can someone at LSI confirm 
> that the delays between each I/O are required, and if so how long they

> must be.
> 
> I'm trying to sort out the use of in/outb_p and where it is 
> unneccessary or used for non ISA devices.
> 
> (Please cc me on the reply)
> Alan
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" 
> in the body of a message to majordomo@vger.kernel.org More majordomo 
> info at  http://vger.kernel.org/majordomo-info.html

--
Intel are signing my paycheques ... these opinions are still mine "Bill,
look, we understand that you're interested in selling us this operating
system, but compare it to ours.  We can't possibly take such a
retrograde step."

Re: Megaraid: Use of outb_p

[Matthew Wilcox]

On Tue, Jan 22, 2008 at 02:30:12PM -0700, Yang, Bo wrote:
> Alan/Matthew,
> 
> I found inb_p/outb_p are defined as inb/outb in kernel src.  So it
> should not have problems to change inb_p/outb_p to inb/outb.

That's not true for x86-32.  Please, can you look up the documentation
for this chip and find out what sort of delay it needs?

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

RE: Megaraid: Use of outb_p

[Yang, Bo]

Alan/Matthew,

I will double check and give you back soon.

Regards.

Bo Yang 

-----Original Message-----
From: Matthew Wilcox [mailto:matthew@wil.cx] 
Sent: Tuesday, January 22, 2008 4:38 PM
To: Yang, Bo
Cc: Alan Cox; linux-scsi@vger.kernel.org; DL-MegaRAID Linux
Subject: Re: Megaraid: Use of outb_p

On Tue, Jan 22, 2008 at 02:30:12PM -0700, Yang, Bo wrote:
> Alan/Matthew,
> 
> I found inb_p/outb_p are defined as inb/outb in kernel src.  So it 
> should not have problems to change inb_p/outb_p to inb/outb.

That's not true for x86-32.  Please, can you look up the documentation
for this chip and find out what sort of delay it needs?

--
Intel are signing my paycheques ... these opinions are still mine "Bill,
look, we understand that you're interested in selling us this operating
system, but compare it to ours.  We can't possibly take such a
retrograde step."

Re: Megaraid: Use of outb_p

[Alan Cox]

On Tue, 22 Jan 2008 14:30:12 -0700
"Yang, Bo" <Bo.Yang@lsi.com> wrote:

> Alan/Matthew,
> 
> I found inb_p/outb_p are defined as inb/outb in kernel src.  So it
> should not have problems to change inb_p/outb_p to inb/outb.

Only on some platforms. On the x86 platforms the inb_p()/outb_p() includes
a 2uS delay while inb/outb do not.

Alan

RE: Megaraid: Use of outb_p

[Yang, Bo]

Alan,

As you pointed out, there are only 2uS difference on x86 platforms for
the changes.  Also the inb_p/outb_p are used for the very old megaraid
scsi controllers.  The src changes should be ok for us.

Regards.

Bo Yang 

-----Original Message-----
From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk] 
Sent: Wednesday, January 23, 2008 5:54 AM
To: Yang, Bo
Cc: Matthew Wilcox; linux-scsi@vger.kernel.org; DL-MegaRAID Linux
Subject: Re: Megaraid: Use of outb_p

On Tue, 22 Jan 2008 14:30:12 -0700
"Yang, Bo" <Bo.Yang@lsi.com> wrote:

> Alan/Matthew,
> 
> I found inb_p/outb_p are defined as inb/outb in kernel src.  So it 
> should not have problems to change inb_p/outb_p to inb/outb.

Only on some platforms. On the x86 platforms the inb_p()/outb_p()
includes a 2uS delay while inb/outb do not.

Alan