Re: [Openocd-development] adapter_khz ... please vote

[Laurent G. <lau...@am...>]

>
> David Brownell wrote:
> >/ On Thursday 25 March 2010, Laurent Gauch wrote:
> />/   
> />>/  ... OK, but we do not resolve the problem by DON'T DO THAT!!
> />>/
> />>/ Actually there are a lot of target scripts working with JTAGkey but not 
> />>/ with JTAGkey-2, 
> />>/     
> />/
> />/ Specifically which ones?
> />/   
> /
> Amontec customers feedback this troubles on
>
> target/pxa270.cfg
> target/pxa255.cfg
> target/sam7se512.cfg
> target/netx500.cfg
> target/samsung_s3c2440.cfg
> ...
> Exhaustive list ? I do not know ...
>
> >/
> />/   
> />>/ just because the JTAGkey-2 run by default at his highest  
> />>/ 30Mhz frequency and because the target does not accept so high JTAG
> />>/     
> />/
> />/ Giving another example of "DON'T DO THAT!!!" ... just make your
> />/ jtagkey2 driver use the same default speed as the original model,
> />/ without needless incompatibilities.
> />/   
> /Yes, this is a workaround but not a solution. You will get the same 
> trouble with other JTAG Dongles allowing a high JTAG frequency as <16Mhz ...
> Example : the STM32 specify a 10MHz in the STM32 BSDL file .
>
> %%%%%%%%Example%%%%%%%%%%%%
> -- This section specifies the TAP ports. For the TAP TCK port, the 
> parameters in the brackets are:
> --        First Field : Maximum  TCK frequency.
> --        Second Field: Allowable states TCK may be stopped in.
>   
>    attribute TAP_SCAN_CLOCK of JTCK  : signal is (10.0e6, BOTH);
>    attribute TAP_SCAN_IN    of JTDI  : signal is true;
>    attribute TAP_SCAN_MODE  of JTMS  : signal is true;
>    attribute TAP_SCAN_OUT   of JTDO  : signal is true;
>    attribute TAP_SCAN_RESET of JTRST : signal is true;
> %%%%%%%%End Of Example%%%%%%%%%
>
> When using JTAGkey-2 (max 30MHz), why should we force the user to use 
> 6MHz (JTAGkey) instead of 10MHz (max of the STM32 specification).
> This will be the same for a Xilinx or Altera target where the actual 
> JTAG frequency can up to 50 to 60 Mhz !
>
> Again, this is not a trouble coming from JTAGkey or JTAGkey-2. This is a 
> trouble coming from openocd allowing to set a JTAG speed to high for a 
> given target !
>
> If we do not provide a robust fix  to this problem, the users will again 
> write their own custom .cfg, on their disk and the openocd community 
> will never get back any new WORKING .cfg !
>
> Any way, we have to set the set the absolute JTAG frequency of the target.
>
> As it is done in the BSDL FILE specification.
>
> -----------------------------------
> T H E   S O L U T I O N 
> -----------------------------------
>
> The solution is to add the absolute max frequency for a given device 
> when we create a "jtag newtap" as
> jtag newtap $_CHIPNAME cpu -freqmax_khz 10000 -irlen 7 -ircapture 0x1 
> -irmask 0x7f -expected-id $_CPUTAPID -expected-id $_CPUTAPID2
>
> This will be the smarter solution I think adding to jtag newtap
> -freqmax_khz xxxxxx
>
> If -freqmax_khz not present (as now) let openocd to use the max 
> frequency of the Dongle (as 30MHz for the Amontec JTAGkey-2)
>
> What do you think. I hope this is the way to go, and we keep the 
> adapter_khz as it is now, to control 'temporary' the JTAG frequency 
> (e.g. startup JTAG frequency ...)
>
> Laurent
>  http://www.amontec.com 
>
>
> >/ The config scripts might still be rather dubious... you would still
> />/ appear to have board configs relying on random driver state instead
> />/ of explicitly setting the right clock rate.
> />/
> />/ But they'd work as well as "before" (switching to jtagkey-2).  Yes?
> />/
> />/   
> /All is great with both Amontec JTAGkey and Amontec JTAGkey-2 (the 
> JTAGkey-3 is really promizing too), they works very well with OpenOCD . 
> That's nice.
> The users can switch from one to an other, without any difficulty.
>
> But the notion of frequency in the actual openocd do not let take all 
> advantages of the speed of the Amontec JTAGkey-2 :-)
>
> Laurent
>  http://www.amontec.com 
>   
We have to implement an arg as -freqmax_khz xxxxx when creating a new 
TAP (jtag newtap ... -freqmax_khz 10000 ...) ?

-freqmax_khz ?
or
-freqmaxkhz ?

Please vote. Thanks.

Regards,
Laurent
 http://www.amontec.com