>> What I did is:
>> 1. add SWD drivers according to the specification
>> Versaloon firmware can do SWD re-transaction if SWD_ACK_OK is not
>> returned, of course there is a max retry count.
>What happens when the retry count expires? OpenOCD shows an error,
>but what state is the target in?
Actually, versaloon will resend automatically, no error will rise in upper
level.
I can try to remove the resend code in Versaloon, and see what will happen.
>> 2. didn't call JTAG specific functions in SWD mode, below is the list.
>> jtag_init_inner(which will run a device detect algorithm on JTAG),
>> tlr reset(because I didn't change the reset script)
>How does device detect and reset work using SWD?
For JTAG:
scan enough 1's after jtag reset and from the data read, IDs of all target
devices are listed.
For SWD:
dap_queue_idcode_read will return the SWD_ID, so that target device can be
detected.
reset is simply to control srst pin, but for jtag, if trst_with_tlr is enabled,
TLR is used.
>> adi_v5_swd.c maybe different, because actually it's originally
>> copied from adi_v5_jtag.c, and OpenOCD has some modification in
>> later commit in adi_v5_swd.c, and I didn't follow because original
>> code is stable.
>Can you say which commit your latest patch is based on?
I really can't remember that, it's more than 2 years ago.
But I can try to test it on the latest code in OpenOCD.
>> About sticky error handler, I use the same method as JTAG, the
>> difference is that when clear sticky error, use SWD method.
>Does this fit also SWD?
Actually, there is jtagdp_transaction_endcheck and swddp_transaction_endcheck,
which will check the stickyerr.
You can refer to swddp_transaction_endcheck, there is even some broken code in
old OpenOCD:
/* Danger!!!! BROKEN!!!! */
adi_swd_scan_inout_check_u32(dap, SWD_DP_DPACC,
DP_CTRL_STAT, DPAP_READ, 0, &ctrlstat);
/* Danger!!!! BROKEN!!!! Why will jtag_execute_queue() fail here????
R956 introduced the check on return value here and now Michael Schwingen reports
that this code no longer works....
https://lists.berlios.de/pipermail/openocd-development/2008-September/003107.html
*/
I think SWD support should be added from high to low, some modification in my
patch is only a work-around, but not a solution.
Versaloon driver can also be added into libswd, or independent from libswd,
it's not the vital point.
The vital problem is that even now, OpenOCD code is too much JTAG dependent, so
that it's not possible to add other transports, even if the transport layer is
ok.
I know which codes in OpenOCD are JTAG dependent.
So if we can somehow make these codes transport independent under some common
point of view, it will be easier for other to add their drivers.
simonqian.openocd
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