On 04/10/13 03:13, Mark Rutland wrote:
>>>> +
>>>> +- #size-cells : Must be 1.
>>>> +
>>>> +- ranges : Indicates parent and child bus address space are the same.
>>>> +
>>> Similarly, what if someone wants to write a more complex mapping for some
>>> reason?
>>>
>>> We should be able to handle it if we use the standard accessors.
>> Maybe I should just leave this part out? They are standard DT properties
>> so I could assume DT writers know what to do.
> I'd be happy with that. It may be worth describing them as "as necessary" or
> something to that effect.
Ok. I added this and removed the property descriptions:
Note that #address-cells, #size-cells, and ranges shall be present to ensure
the CPU can address a frame's registers.
> I can see why we need to specify secure/non-secure, but I'm not sure why we
> need to specify hyp/user/kernel usage. Could we not leave this up to the kernel
> to figure out?
>
> A basic overveiew for those that don't know about the memory mapped timers:
>
> * There's one control frame CNTCTLBase. Some registers in this frame are only
> available for secure accesses, including CNTNSAR which sets whether the
> counter frames are accessible from the non-secure side.
>
> * There are up to 8 timer frames, which have their own CNTVOFF and
> physical/virtual timers. Each frame CNTBaseN is duplicated at CNTPL0BaseN
> with CNTVOFF and CNTPL0ACR (which controls PL0 accesses) inaccessible.
>
> I can see that we might have frames/registers we can't access (if we were
> booted on the non-secure side), but I can't see anything limiting whether we
> use a frame for kernel/hyp/user beyond that. Have I missed something?
>
> Could we not have something like the following for each frame:
>
> frame0 {
> frame-id = <0>;
> status = "disabled"; /* booted NS, secure firmware has not enabled access */
> reg = <0x... 0x1000>, /* CNTBase0 */
> <0x... 0x1000>; /* CNTPL0Base0 */
> };
>
I don't think you're missing anything. Technically the second view is
not always implemented though. Using the status property should be
sufficient I think.
>> Also to get the frame number, I was thinking maybe we should expand the
>> reg property to have two address cells. Then we could have reg = <0
>> 0xf0001000 0x1000>.
> We could do that, but then you definitely need a more complex ranges property,
> and additional parsing code to handle grabbing it out of the reg property. I
> can't see what it buys us.
Ok. It would mandate node names like "frame@0", "frame@1", but I'll drop
the idea unless someone else finds it useful.
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
--
To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
