[PATCH]: 4545cc2cdb jtag/drivers: fix reset logic handling in OpenJTAG

[gerrit]

This is an automated email from Gerrit.

"N S <nlsh...@yahoo.com>" just uploaded a new patch set to Gerrit, which you 
can find at https://review.openocd.org/c/openocd/+/8121

-- gerrit

commit 4545cc2cdbd6bf201eee0ccc1496434dffe19cea
Author: N S <nlsh...@yahoo.com>
Date:   Mon Jan 22 21:47:34 2024 -0800

    jtag/drivers: fix reset logic handling in OpenJTAG
    
    The OpenJTAG driver behaviour always forces a system reset on jtag_init.
    The driver was incorrectly assuming that when execute_reset is called
    with trst set to 1 - perform a software TAP reset, otherwise perform a
    system reset when trst is 0.
    
    The set_state call assumes the that OpenJTAG hardware will perform a
    software TLR reset if the target state is TAP_RESET. This is not the
    case: the published VHDL will simply find the shortest path to TLR and
    not perform a fixed 5 cycle operation with TMS held high.
    
    Fix the code to only perform system resets when srst is 1 in
    execute_reset and to force a software TAP reset operation in set_state
    when the target state is TAP_RESET.
    
    Change-Id: I7e0f76f8491efefff1ccaeb4b1ae16e722d76df4
    Signed-off-by: N S <nlsh...@yahoo.com>

diff --git a/src/jtag/drivers/openjtag.c b/src/jtag/drivers/openjtag.c
index dca27b0a64..387eda64b8 100644
--- a/src/jtag/drivers/openjtag.c
+++ b/src/jtag/drivers/openjtag.c
@@ -660,14 +660,12 @@ static void openjtag_execute_reset(struct jtag_command 
*cmd)
 
        uint8_t buf = 0x00;
 
-       if (cmd->cmd.reset->trst) {
-               buf = 0x03;
-       } else {
+       /* Pull SRST low for 5 TCLK cycles */
+       if (cmd->cmd.reset->srst) {
                buf |= 0x04;
                buf |= 0x05 << 4;
+               openjtag_add_byte(buf);
        }
-
-       openjtag_add_byte(buf);
 }
 
 static void openjtag_execute_sleep(struct jtag_command *cmd)
@@ -680,8 +678,14 @@ static void openjtag_set_state(uint8_t openocd_state)
        uint8_t state = openjtag_get_tap_state(openocd_state);
 
        uint8_t buf = 0;
-       buf = 0x01;
-       buf |= state << 4;
+
+       if (state != OPENJTAG_TAP_RESET) {
+               buf = 0x01;
+               buf |= state << 4;
+       } else {
+               /* Force software TLR */
+               buf = 0x03;
+       }
 
        openjtag_add_byte(buf);
 }

--