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drivers/swd: add support for SWD multidrop 

According to ARM IHI0031C+ chapter 2.3.11 "TARGETSEL, Target Selection register"
multidrop capable DPv2 must not drive SWDIO line during the response phase
of a write to TARGETSEL register.

Introduce helper functions swd_cmd_returns_ack() and swd_ack_to_error_code()
to centralize these tests from all drivers to one place.

Introduce distinct error codes for SWD protocol.

Partly inspired by Graham Sanderson's http://review.openocd.org/4935

Change-Id: Ie5f9edb22e066a933a534bf2b29e7e1d3087dad1
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6699
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins
This commit is contained in:
Tomas Vanek 2021-11-12 09:49:01 +01:00 committed by Antonio Borneo
parent 3eef83e4bd
commit 872682345a
1 changed files with 41 additions and 0 deletions
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41
src/jtag/swd.h
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@ -18,6 +18,7 @@
#ifndef OPENOCD_JTAG_SWD_H
#define OPENOCD_JTAG_SWD_H
#include <helper/log.h>
#include <target/arm_adi_v5.h>
/* Bits in SWD command packets, written from host to target
@ -32,6 +33,12 @@
#define SWD_CMD_PARK (1 << 7) /* driven high by host */
/* followed by TRN, 3-bits of ACK, TRN */
/*
* The SWD subsystem error codes
*/
#define ERROR_SWD_FAIL (-400) /** protocol or parity error */
#define ERROR_SWD_FAULT (-401) /** device returned FAULT in ACK field */
/**
* Construct a "cmd" byte, in lSB bit order, which swd_driver.read_reg()
* and swd_driver.write_reg() methods will use directly.
@ -53,6 +60,40 @@ static inline uint8_t swd_cmd(bool is_read, bool is_ap, uint8_t regnum)
/* SWD_ACK_* bits are defined in <target/arm_adi_v5.h> */
/**
* Test if we can rely on ACK returned by SWD command
*
* @param cmd Byte constructed by swd_cmd(), START, STOP and TRN are filtered off
* @returns true if ACK should be checked, false if should be ignored
*/
static inline bool swd_cmd_returns_ack(uint8_t cmd)
{
uint8_t base_cmd = cmd & (SWD_CMD_APNDP | SWD_CMD_RNW | SWD_CMD_A32);
/* DPv2 does not reply to DP_TARGETSEL write cmd */
return base_cmd != swd_cmd(false, false, DP_TARGETSEL);
}
/**
* Convert SWD ACK value returned from DP to OpenOCD error code
*
* @param ack
* @returns error code
*/
static inline int swd_ack_to_error_code(uint8_t ack)
{
switch (ack) {
case SWD_ACK_OK:
return ERROR_OK;
case SWD_ACK_WAIT:
return ERROR_WAIT;
case SWD_ACK_FAULT:
return ERROR_SWD_FAULT;
default:
return ERROR_SWD_FAIL;
}
}
/*
* The following sequences are updated to
* ARM(tm) Debug Interface v5 Architecture Specification ARM IHI 0031E