Re: Megaraid: Use of outb_p

[Matthew Wilcox <matthew@wil.cx>]

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
> 
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