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jtag: cmsis-dap: Issue disconnect before reconnecting 

cmsis-dap protocol has both DAP_Connect and DAP_Disconnect commands.
Logically if cmsis_dap_swd_switch_seq() calls DAP_Connect in connected
state it should call DAP_Disconnect first.

Doing so surprisingly solves problems on Atmel EDBG with target SAMD/R/L/C.
Without this change SWD communication breaks after reset run/halt
in config "reset_config srst_only" and reconnect trials repeatedly
fail with "SWD ack not OK: 0 JUNK"

Change-Id: Ie951098d5e0c83f388e2df414608aaabec2135c9
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/3098
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
This commit is contained in:
Tomas Vanek 2015-11-05 21:05:43 +01:00 committed by Spencer Oliver
parent 751e2454bf
commit 72c3464be4
1 changed files with 3 additions and 0 deletions
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3
src/jtag/drivers/cmsis_dap_usb.c
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@ -714,6 +714,9 @@ static int cmsis_dap_swd_switch_seq(struct adiv5_dap *dap, enum swd_special_seq
unsigned int s_len;
int retval;
/* First disconnect before connecting, Atmel EDBG needs it for SAMD/R/L/C */
cmsis_dap_cmd_DAP_Disconnect();
/* When we are reconnecting, DAP_Connect needs to be rerun, at
* least on Keil ULINK-ME */
retval = cmsis_dap_cmd_DAP_Connect(seq == LINE_RESET || seq == JTAG_TO_SWD ?