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Fix REQUEST/GRANT/SACK: "A device may not accept a grant (assert SACK) after it passes the grant"

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This commit is contained in:
Joerg Hoppe
2019-11-02 16:29:17 +01:00
parent 48f10ed34b
commit aef4854a88
3 changed files with 23 additions and 9 deletions
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10
10.01_base/2_src/pru1/pru1_main_unibus.c
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@@ -159,9 +159,11 @@ void main(void) {
// "set" is inverting!
cpu_grant_mask = buslatches_getbyte(0) & PRIORITY_ARBITRATION_BIT_MASK; // read GRANT IN
// forward un-requested GRANT IN to GRANT OUT for other cards on neighbor slots
uint8_t grant_out_mask = cpu_grant_mask & ~sm_arb.device_request_mask ;
buslatches_setbits(0, PRIORITY_ARBITRATION_BIT_MASK, ~grant_out_mask)
;
sm_arb.device_forwarded_grant_mask = cpu_grant_mask
& ~sm_arb.device_request_signalled_mask;
buslatches_setbits(0, PRIORITY_ARBITRATION_BIT_MASK, ~sm_arb.device_forwarded_grant_mask)
;
// "A device may not accept a grant (assert SACK) after it passes the grant"
}
// handle GRANT/SACK/BBSY for emulated devices
uint8_t granted_request = sm_device_arb_worker(cpu_grant_mask); // devices process GRANT
@@ -293,7 +295,7 @@ void main(void) {
mailbox.arm2pru_req = ARM2PRU_NONE; // ACK: done
break;
case ARM2PRU_BUSLATCH_SET: { // set a mux register
// and read back
// and read back
// don't feed "volatile" vars into buslatch_macros !!!
uint8_t reg_sel = mailbox.buslatch.addr & 7;
uint8_t bitmask = mailbox.buslatch.bitmask;

10
10.01_base/2_src/pru1/pru1_statemachine_arbitration.c
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@@ -100,8 +100,11 @@ void sm_arb_reset() {
// cleanup: clear all REQUESTS and SACK
buslatches_setbits(1, PRIORITY_ARBITRATION_BIT_MASK | BIT(5), 0);
sm_arb.device_request_mask = 0;
sm_arb.device_forwarded_grant_mask = 0;
sm_arb.device_request_signalled_mask = 0;
sm_arb.bbsy_wait_grant_mask = 0;
sm_arb.cpu_request = 0 ;
sm_arb.cpu_request = 0;
sm_arb.arbitrator_grant_mask = 0;
timeout_cleanup(TIMEOUT_SACK);
}
@@ -171,6 +174,8 @@ uint8_t sm_arb_worker_device(uint8_t grant_mask) {
// Always update UNIBUS BR/NPR lines, are ORed with requests from other devices.
buslatches_setbits(1, PRIORITY_ARBITRATION_BIT_MASK, sm_arb.device_request_mask)
;
// now relevant for GRANt forwarding
sm_arb.device_request_signalled_mask = sm_arb.device_request_mask;
// read GRANT IN lines from CPU (Arbitrator).
// Only one nit ion cpu_grant_mask at a time may be active, else arbitrator malfunction.
@@ -179,7 +184,8 @@ uint8_t sm_arb_worker_device(uint8_t grant_mask) {
if (sm_arb.bbsy_wait_grant_mask == 0) {
// State 1: Wait For GRANT:
// process the requested grant for an open requests.
grant_mask &= sm_arb.device_request_mask;
// "A device may not accept a grant (assert SACK) after it passes the grant"
grant_mask &= (sm_arb.device_request_mask & ~sm_arb.device_forwarded_grant_mask);
if (grant_mask) {
// one of our requests was granted:
// set SACK

12
10.01_base/2_src/pru1/pru1_statemachine_arbitration.h
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@@ -42,6 +42,12 @@ typedef struct {
// BR/NPR lines = set of _PRIORITY_ARBITRATION_BIT_*
uint8_t device_request_mask;
// device_request_mask when actually on BR/NR lines
uint8_t device_request_signalled_mask;
// forwarded to GRANT OUT, not accepted as response to device_request_signalled_mask
uint8_t device_forwarded_grant_mask;
// sm_arb has 2 states: State 1 "Wait for GRANT" and State 2 "wait for BBSY"
// When arbitrator GRANts a request, we set SACK, GRAMT is cleared and we wait
// for BBSY clear.
@@ -51,11 +57,11 @@ typedef struct {
/*** master ****/
// CPU is requesting memory access via PRU2ARM_DMA/mailbox.dma
uint8_t cpu_request ;
uint8_t cpu_request;
uint8_t arbitrator_grant_mask; // single GRANT line set by master
// uint8_t dummy[3] ;
uint8_t dummy[2]; // make it dword-sized
} statemachine_arbitration_t;