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ARM ADIv5: add comments 

Add doxygen and other comments for what's more or less the lowest
level JDAG-DP primitive, to access JTAG_DP_{A,D}PACC registers.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
This commit is contained in:
David Brownell 2010-01-14 12:58:39 -08:00
parent 1d140c4dcd
commit 8e1b5c3138
1 changed files with 27 additions and 1 deletions
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28
src/target/arm_adi_v5.c
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@ -88,7 +88,24 @@ static uint32_t max_tar_block_size(uint32_t tar_autoincr_block, uint32_t address
* *
***************************************************************************/
/* Scan out and in from target ordered uint8_t buffers */
/**
* Scan DPACC or APACC using target ordered uint8_t buffers. No endianness
* conversions are performed. See section 4.4.3 of the ADIv5 spec, which
* discusses operations which access these registers.
*
* Note that only one scan is performed. If RnW is set, a separate scan
* will be needed to collect the data which was read; the "invalue" collects
* the posted result of a preceding operation, not the current one.
*
* @param swjdp the DAP
* @param instr JTAG_DP_APACC (AP access) or JTAG_DP_DPACC (DP access)
* @param reg_addr two significant bits; A[3:2]; for APACC access, the
* SELECT register has more addressing bits.
* @param RnW false iff outvalue will be written to the DP or AP
* @param outvalue points to a 32-bit (little-endian) integer
* @param invalue NULL, or points to a 32-bit (little-endian) integer
* @param ack points to where the three bit JTAG_ACK_* code will be stored
*/
static int adi_jtag_dp_scan(struct swjdp_common *swjdp,
uint8_t instr, uint8_t reg_addr, uint8_t RnW,
uint8_t *outvalue, uint8_t *invalue, uint8_t *ack)
@ -104,6 +121,7 @@ static int adi_jtag_dp_scan(struct swjdp_common *swjdp,
/* REVISIT these TCK cycles should be *AFTER* updating APACC, since
* they provide more time for the (MEM) AP to complete the read ...
* See "Minimum Response Time" for JTAG-DP, in the ADIv5 spec.
*/
if ((instr == JTAG_DP_APACC)
&& ((reg_addr == AP_REG_DRW)
@ -111,12 +129,20 @@ static int adi_jtag_dp_scan(struct swjdp_common *swjdp,
&& (swjdp->memaccess_tck != 0))
jtag_add_runtest(swjdp->memaccess_tck, jtag_set_end_state(TAP_IDLE));
/* Scan out a read or write operation using some DP or AP register.
* For APACC access with any sticky error flag set, this is discarded.
*/
fields[0].tap = jtag_info->tap;
fields[0].num_bits = 3;
buf_set_u32(&out_addr_buf, 0, 3, ((reg_addr >> 1) & 0x6) | (RnW & 0x1));
fields[0].out_value = &out_addr_buf;
fields[0].in_value = ack;
/* NOTE: if we receive JTAG_ACK_WAIT, the previous operation did not
* complete; data we write is discarded, data we read is unpredictable.
* When overrun detect is active, STICKYORUN is set.
*/
fields[1].tap = jtag_info->tap;
fields[1].num_bits = 32;
fields[1].out_value = outvalue;