[ECOS] 8260 driver cannot access DPRAM

[ECOS] 8260 driver cannot access DPRAM

[Todd Smith]

I am writing an HDLC driver using SCC3 on an 8250 (an 8260 variant). 
Using a build a coworker has done for the rattler card, I've started on 
a basic driver. My problem is that my code cannot access the DPRAM. 
Using the address 0x04700000 as the base of this RAM, I get a 
segmentation violation when I try to access anything there. In fact, gdb 
can't even access that memory (e.g. when I try to dump at that address). 
I know this is the same memory the serial and ethernet driver also 
access so it must be possible. Seems like some memory protection is 
going on. In an attempt to take some baby steps and get something basic 
running, I have not added my driver as a package (not sure if this makes 
a difference) but I have added an init function to the drivers table via 
the DEVTAB_ENTRY macro. The init function gets a segmentation violation 
as soon as it tries to access the cpcr register in the DPRAM.

Any help would be greatly appreciated.

--Todd




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Re: [ECOS] 8260 driver cannot access DPRAM

[Gary Thomas]

On Mon, 2003-09-29 at 14:41, Todd Smith wrote:
> I am writing an HDLC driver using SCC3 on an 8250 (an 8260 variant). 
> Using a build a coworker has done for the rattler card, I've started on 
> a basic driver. My problem is that my code cannot access the DPRAM. 
> Using the address 0x04700000 as the base of this RAM, I get a 
> segmentation violation when I try to access anything there. In fact, gdb 
> can't even access that memory (e.g. when I try to dump at that address). 
> I know this is the same memory the serial and ethernet driver also 
> access so it must be possible. Seems like some memory protection is 
> going on. In an attempt to take some baby steps and get something basic 
> running, I have not added my driver as a package (not sure if this makes 
> a difference) but I have added an init function to the drivers table via 
> the DEVTAB_ENTRY macro. The init function gets a segmentation violation 
> as soon as it tries to access the cpcr register in the DPRAM.
> 

The Rattler DPRAM is not at 0x04700000 :-(

Try using CYGARC_IMM_BASE (0xFF000000) instead.  You also might look at
some of the other drivers for that platform to see how the CPM is
accessed.

-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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Re: [ECOS] 8260 driver cannot access DPRAM

[Christoph Csebits]

On Mon, Sep 29, 2003 at 02:41:48PM -0600, Todd Smith wrote:
> Using the address 0x04700000 as the base of this RAM, I get a 
> segmentation violation when I try to access anything there. In fact, gdb 
> can't even access that memory (e.g. when I try to dump at that address). 

take a look at
http://sources.redhat.com/ml/ecos-discuss/2002-11/msg00224.html

regards, christoph
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