83xx: Marking or Allocating Pages as Cache-Inhibited

[Liu Dave-R63238]

and what settings  is DMA description bit 3?

> -----Original Message-----
> From: linuxppc-dev-bounces+daveliu=freescale.com at ozlabs.org 
> [mailto:linuxppc-dev-bounces+daveliu=freescale.com at ozlabs.org]
>  On Behalf Of Liu Dave-R63238
> Sent: Friday, March 06, 2009 1:22 PM
> To: Ben Menchaca; linuxppc-dev at ozlabs.org
> Subject: RE: 83xx: Marking or Allocating Pages as Cache-Inhibited
> 
> Did you enable the snoop bit at PEX_WDMA_CTRL[SNOOP] and 
> PEX_RDMA_CTRL[SNOOP]?
> 
> What is the freq settings? CORE/CSB bus.
> 
> Thanks, Dave
> 
> ________________________________
> 
> 	From: linuxppc-dev-bounces+daveliu=freescale.com at ozlabs.org
> [mailto:linuxppc-dev-bounces+daveliu=freescale.com at ozlabs.org]
>  On Behalf Of Ben Menchaca
> 	Sent: Friday, March 06, 2009 12:33 PM
> 	To: linuxppc-dev at ozlabs.org
> 	Subject: 83xx: Marking or Allocating Pages as Cache-Inhibited
> 	
> 	
> 	I am working on a Freescale 8314e design, and the 
> embedded device is configured as a PCI-e endpoint running a 
> 2.6.27-5 kernel.  For context, we have written a kernel 
> module which, among other things, uses the RDMA/WDMA engine 
> in the PCI-e IP block.  On the host side, these DMAs are 
> coherent.  However, on the embedded side, things are quite a 
> bit less rosy; we must manually flush/invalidate cache lines 
> for WDMA/RDMAs to occur successfully.  After speaking with 
> (several) FAEs at Freescale, we believe there is a 
> configuration issue that is the cause, but we have yet to 
> have anyone successfully point to it.  
> 	
> 	Disabling the data cache altogether resolves the issue 
> entirely, but of course, also completely tanks performance.  
> As a temporary workaround, I would like to simply mark the 
> pages (obtained currently via dma_alloc_coherent) involved as 
> cache-inhibited.  I have attempted to do this via some 
> snippets remaining in fec.c (va_to_pte, uncache_pte to set 
> _PAGE_NO_CACHE, flush_tlb_page, then unmap_pte), but this is 
> almost certainly braindead; va_to_pte is not a part of the 
> 83xx source, as far as I can tell; 8xx only.
> 	
> 	A quick pointer in the correct direction for marking 
> pages as cache-inhibited on a 2.6.27-5 kernel would be 
> appreciated, or if my approach to a workaround is flawed, a 
> pointer to the correct way would be great.
> 	
> 	Ben Menchaca
> 	
> 
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