SDIO Performance once again

[Dominik S. Herwald]

Robin Getz schrieb:
> On Mon 9 Feb 2009 08:09, Dominik S. Herwald pondered:
>   
>> In the meantime I found out that my Problem seems to be related to the 
>> Kernel timer tick of 4ms
>> (see my second posting on this list with the 4ms frames)...
>> On Blackfin the Timer tick is set to 250Hz (4ms) by default. If I set it
>>
>> to 1000Hz,
>> performance rises up to 11.2MBit/s performance!
>>     
>
> What happens when you select tickless?
>
> Select GENERIC_TIME && GENERIC_CLOCKEVENTS && CYCLES_CLOCKSOURCE
>
> And it should show up as "Tickless System (Dynamic Ticks)".
>
> -Robin
>
>   

It performs the same (11MBit/s) as with 1000Hz Timer tick.
On the Scope I can see a 1ms transfer interval instead of 4ms. 
There is still plenty of room in between the transfers on the SDIO Bus...

If I set the Clock to 250Hz while these tickless options are active, the 4ms
Interval is there again.


I had a closer look at the Libertas Code - nearly everywhere in Libertas 
the Kernel Tick
is only used for timeouts in the range of seconds. I did not see 
anything that could
affect the transfer.  But I am really no Kernel Driver expert so I may 
have overlooked
something...

Best regards,
Dominik