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Pin down alignment for writeDataLoop and readDataLoop, and perform some additional timing adjustment.

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This commit is contained in:
Glenn Anderson 2022-03-18 15:51:22 -07:00
parent b797793340
commit dd87235fc0
1 changed files with 45 additions and 20 deletions
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65
src/BlueSCSI.cpp
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@ -743,27 +743,35 @@ void writeDataPhase(int len, const byte* p)
}
#if READ_SPEED_OPTIMIZE
#pragma GCC push_options
#pragma GCC optimize ("-Os")
/*
* This loop is tuned to repeat the following pattern:
* 1) Set REQ
* 2) 5-6 cycles of work/delay
* 2) 5 cycles of work/delay
* 3) Wait for ACK
* Cycle time tunings are for 72MHz STM32F103
* Alignment matters. For the 3 instruction wait loops,it looks like crossing
* an 8 byte prefetch buffer can add 2 cycles of wait every branch taken.
*/
void writeDataLoop(uint32_t blocksize) __attribute__ ((aligned(8)));
void writeDataLoop(uint32_t blocksize)
{
#define REQ_ON() (*db_dst = BITMASK(vREQ)<<16);
#define REQ_ON() (port_b->BRR = req_bit);
#define FETCH_BSRR_DB() (bsrr_val = bsrr_tbl[*srcptr++])
#define REQ_OFF_DB_SET(BSRR_VAL) *db_dst = BSRR_VAL;
#define WAIT_ACK_ACTIVE() while(!SCSI_IN(vACK))
#define WAIT_ACK_INACTIVE() while(SCSI_IN(vACK))
#define REQ_OFF_DB_SET(BSRR_VAL) port_b->BSRR = BSRR_VAL;
#define WAIT_ACK_ACTIVE() while((*port_a_idr>>(vACK&15)&1))
#define WAIT_ACK_INACTIVE() while(!(*port_a_idr>>(vACK&15)&1))
register byte *srcptr= m_buf; // Source buffer
register byte *endptr= m_buf + blocksize; // End pointer
register const uint32_t *bsrr_tbl = db_bsrr; // Table to convert to BSRR
register uint32_t bsrr_val; // BSRR value to output (DB, DBP, REQ = ACTIVE)
register volatile uint32_t *db_dst = &(GPIOB->regs->BSRR); // Output port
register uint32_t req_bit = BITMASK(vREQ);
register gpio_reg_map *port_b = PBREG;
register volatile uint32_t *port_a_idr = &(GPIOA->regs->IDR);
// Start the first bus cycle.
FETCH_BSRR_DB();
@ -772,19 +780,19 @@ void writeDataLoop(uint32_t blocksize)
FETCH_BSRR_DB();
WAIT_ACK_ACTIVE();
REQ_OFF_DB_SET(bsrr_val);
// Align the starts of the do/while and WAIT loops to an 8 byte prefetch.
asm("nop.w;nop");
do{
WAIT_ACK_INACTIVE();
REQ_ON();
// 6 cycle delay before reading ACK.
// Store plus 2 loads is 6 cycles.
REQ_ON();
// 4 cycles of work
FETCH_BSRR_DB();
// Extra 1 cycle delay while keeping the loop within an 8 byte prefetch.
asm("nop");
WAIT_ACK_ACTIVE();
REQ_OFF_DB_SET(bsrr_val);
// 5 cycle delay before reading ACK.
// Branch taken is 2-4, seems to be taking 3. A second write is 2 more cycles.
// cmp is being pipelined in to a store so doesn't add any time.
REQ_OFF_DB_SET(bsrr_val);
// Extra 1 cycle delay, plus 4 cycles for the branch taken with prefetch.
asm("nop");
}while(srcptr < endptr);
WAIT_ACK_INACTIVE();
// Finish the last bus cycle, byte is already on DB.
@ -793,6 +801,7 @@ void writeDataLoop(uint32_t blocksize)
REQ_OFF_DB_SET(bsrr_val);
WAIT_ACK_INACTIVE();
}
#pragma GCC pop_options
#endif
/*
@ -841,32 +850,48 @@ void readDataPhase(int len, byte* p)
p[i] = readHandshake();
}
#if WRITE_SPEED_OPTIMIZE
#pragma GCC push_options
#pragma GCC optimize ("-Os")
/*
* See writeDataLoop for optimization info.
*/
void readDataLoop(uint32_t blockSize) __attribute__ ((aligned(8)));
void readDataLoop(uint32_t blockSize)
{
register byte *dstptr= m_buf;
register byte *endptr= m_buf + blockSize - 1;
#define REQ_ON() (port_b->BSRR = BITMASK(vREQ)<<16);
#define REQ_OFF() (port_b->BSRR = BITMASK(vREQ));
#define WAIT_ACK_ACTIVE() while((*ack_src>>(vACK&15)&1))
#define WAIT_ACK_INACTIVE() while(!(*ack_src>>(vACK&15)&1))
#define REQ_ON() (port_b->BRR = req_bit);
#define REQ_OFF() (port_b->BSRR = req_bit);
#define WAIT_ACK_ACTIVE() while((*port_a_idr>>(vACK&15)&1))
#define WAIT_ACK_INACTIVE() while(!(*port_a_idr>>(vACK&15)&1))
register uint32_t req_bit = BITMASK(vREQ);
register gpio_reg_map *port_b = PBREG;
register volatile uint32_t *ack_src = &(GPIOA->regs->IDR);
register volatile uint32_t *port_a_idr = &(GPIOA->regs->IDR);
REQ_ON();
// Start of the do/while and WAIT are already aligned to 8 bytes.
do {
WAIT_ACK_ACTIVE();
uint32_t ret = GPIOB->regs->IDR;
uint32_t ret = port_b->IDR;
REQ_OFF();
*dstptr++ = ~(ret >> 8);
// Move wait loop in to a single 8 byte prefetch buffer
asm("nop.w");
WAIT_ACK_INACTIVE();
REQ_ON();
// Extra 1 cycle delay
asm("nop");
} while(dstptr<endptr);
WAIT_ACK_ACTIVE();
uint32_t ret = GPIOB->regs->IDR;
REQ_OFF();
*dstptr++ = ~(ret >> 8);
*dstptr = ~(ret >> 8);
WAIT_ACK_INACTIVE();
}
#pragma GCC pop_options
#endif
/*
* Data out phase.