Re: Some IDE issues with 2.6.28 on PC-Engines ALIX2

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Alan Cox wrote:

>>>The IDE interface of the Geode CS5536 companion chip is a completely
>>>different beast.  It's a more or less standard AMD 8111 PCI IDE device
>>>with slightly different timings.

>>   I'm not sure I uderstand the passage about "slightly different 
>>timings"...

> The timing values used are different to those on the AMD 8111 even though
> the interface is similar.

    What do you mean by timing values anyway, clock counts or the register 
encoding itself?

>>   It's stange that the driver is using CPI config. space by default 
>>which not even documented in the datasheet. I guess the MSR accesses are 

> The PCI configuration is the portable way to drive it.

    Portable to what? As you have yorself noted below, this is Geode -- and I 
highly doubt that CS5536 will be used for anything else.

>>also somewhat faster because one doesn't have to access the address/data 
>>register pair at ports 0xcf8/0xcfc...

> This is a Geode.

    I know. :-)
    I have hacked on older Geode GX2 for some time back in 2004 (although not 
on something related to PCI); my "toy" board has RIP just recently.)

> What makes you think there is even a PCI bus 

    I sure know that it's not PCI (IIUC, it's the common tendency in the x86 
north-to-south-bridge busses has been emulating the PCI config. space with 
less and less PCI compatible "physical layer"). That does mean emulating PCI 
config. space mechanism #1 and Geode's not an exception here, see:

http://www.amd.com/files/connectivitysolutions/geode/geode_gx/32663C_lx_gx_pciconfig.pdf

> or that the 8111 interface isn't entirely a software construct.

    If that's the case (looks like so), it makes using it even appealing...

> Geode PCI hardware is mostly smoke and mirrors ;)

    When it comes to their internal controllers, yes (though e.g. their OHCI 
seem to have the real PCI config. space).

> Alan

WBR, Sergei