What if I am using Intel's XScale (80310) which is ARM architecture ?
From: Ravi <kravi26@yahoo.com>
To: shesha bhushan <bhushan_vadulas@hotmail.com>, kernelnewbies@nl.linux.org
Subject: Re: What does pci_map_single do ?
Date: Wed, 19 Feb 2003 09:43:18 -0800 (PST)
--- shesha bhushan <bhushan_vadulas@hotmail.com> wrote:
> 1. pci_map_single will transfer the data from RAM (kernel
> area) to the hardware accessible area and will provide
> with a pointer which can then be passed to the hardware.
> 2. In the above function the "size" parameter indicates
> the amount of DMA transfer.
> Am I correct in the above two points? If I am wrong please
> correct me.
pci_map_single() is architecture specific. On Intel i386,
it just returns the physical address corresponding to the
virtual address passed in as parameter, no copying is done.
The size parameter is ignored.
> In the Linux Device driver book (page 408), he says, data
> must be explicitly flushed from the processor cache. And
> data flushed this way is not avaliable to the device.
>
> This means that we must flush the processor cache before
> calling pci_map_single. How can we achieve this.
I didn't understand that fully. But I guess the call to
flush_write_buffers() in pci_map_single() (again, this is
for Intel i386) does what you are looking for.
Hope this helps.
-Ravi.
__________________________________________________
Do you Yahoo!?
Yahoo! Shopping - Send Flowers for Valentine's Day
http://shopping.yahoo.com
_________________________________________________________________
Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
