drm/amd/display: Fix DMUB reset sequence for DCN401

[ Upstream commit 0dfcc2bf269010a6e093793034c048049a40ee93 ]

[WHY]
It should no longer use DMCUB_SOFT_RESET as it can result
in the memory request path becoming desynchronized.

[HOW]
To ensure robustness in the reset sequence:
1) Extend timeout on the "halt" command sent via gpint, and check for
controller to enter "wait" as a stronger guarantee that there are no
requests to memory still in flight.
2) Remove usage of DMCUB_SOFT_RESET
3) Rely on PSP to reset the controller safely

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/amd/display/dmub/src/dmub_dcn401.c

@@ -63,8 +63,10 @@ static inline void dmub_dcn401_translate_addr(const union dmub_addr *addr_in,
 void dmub_dcn401_reset(struct dmub_srv *dmub)
 {
 	union dmub_gpint_data_register cmd;
-	const uint32_t timeout = 30;
+	const uint32_t timeout_us = 1 * 1000 * 1000; //1s
-	uint32_t in_reset, scratch, i;
+	const uint32_t poll_delay_us = 1; //1us
+	uint32_t i = 0;
+	uint32_t in_reset, scratch, pwait_mode;
 
 	REG_GET(DMCUB_CNTL2, DMCUB_SOFT_RESET, &in_reset);
 
@@ -75,32 +77,35 @@ void dmub_dcn401_reset(struct dmub_srv *dmub)
 
 		dmub->hw_funcs.set_gpint(dmub, cmd);
 
-		/**
+		for (i = 0; i < timeout_us; i++) {
-		 * Timeout covers both the ACK and the wait
-		 * for remaining work to finish.
-		 *
-		 * This is mostly bound by the PHY disable sequence.
-		 * Each register check will be greater than 1us, so
-		 * don't bother using udelay.
-		 */
-
-		for (i = 0; i < timeout; ++i) {
 			if (dmub->hw_funcs.is_gpint_acked(dmub, cmd))
 				break;
+
+			udelay(poll_delay_us);
 		}
 
-		for (i = 0; i < timeout; ++i) {
+		for (; i < timeout_us; i++) {
 			scratch = dmub->hw_funcs.get_gpint_response(dmub);
 			if (scratch == DMUB_GPINT__STOP_FW_RESPONSE)
 				break;
+
+			udelay(poll_delay_us);
 		}
 
-		/* Force reset in case we timed out, DMCUB is likely hung. */
+		for (; i < timeout_us; i++) {
+			REG_GET(DMCUB_CNTL, DMCUB_PWAIT_MODE_STATUS, &pwait_mode);
+			if (pwait_mode & (1 << 0))
+				break;
+
+			udelay(poll_delay_us);
+		}
+	}
+
+	if (i >= timeout_us) {
+		/* timeout should never occur */
+		BREAK_TO_DEBUGGER();
 	}
 
-	REG_UPDATE(DMCUB_CNTL2, DMCUB_SOFT_RESET, 1);
-	REG_UPDATE(DMCUB_CNTL, DMCUB_ENABLE, 0);
-	REG_UPDATE(MMHUBBUB_SOFT_RESET, DMUIF_SOFT_RESET, 1);
 	REG_WRITE(DMCUB_INBOX1_RPTR, 0);
 	REG_WRITE(DMCUB_INBOX1_WPTR, 0);
 	REG_WRITE(DMCUB_OUTBOX1_RPTR, 0);
@@ -131,7 +136,10 @@ void dmub_dcn401_backdoor_load(struct dmub_srv *dmub,
 
 	dmub_dcn401_get_fb_base_offset(dmub, &fb_base, &fb_offset);
 
+	/* reset and disable DMCUB and MMHUBBUB DMUIF */
 	REG_UPDATE(DMCUB_SEC_CNTL, DMCUB_SEC_RESET, 1);
+	REG_UPDATE(MMHUBBUB_SOFT_RESET, DMUIF_SOFT_RESET, 1);
+	REG_UPDATE(DMCUB_CNTL, DMCUB_ENABLE, 0);
 
 	dmub_dcn401_translate_addr(&cw0->offset, fb_base, fb_offset, &offset);
 
@@ -151,6 +159,7 @@ void dmub_dcn401_backdoor_load(struct dmub_srv *dmub,
 			DMCUB_REGION3_CW1_TOP_ADDRESS, cw1->region.top,
 			DMCUB_REGION3_CW1_ENABLE, 1);
 
+	/* release DMCUB reset only to prevent premature execution */
 	REG_UPDATE_2(DMCUB_SEC_CNTL, DMCUB_SEC_RESET, 0, DMCUB_MEM_UNIT_ID,
 			0x20);
 }
@@ -161,7 +170,10 @@ void dmub_dcn401_backdoor_load_zfb_mode(struct dmub_srv *dmub,
 {
 	union dmub_addr offset;
 
+	/* reset and disable DMCUB and MMHUBBUB DMUIF */
 	REG_UPDATE(DMCUB_SEC_CNTL, DMCUB_SEC_RESET, 1);
+	REG_UPDATE(MMHUBBUB_SOFT_RESET, DMUIF_SOFT_RESET, 1);
+	REG_UPDATE(DMCUB_CNTL, DMCUB_ENABLE, 0);
 
 	offset = cw0->offset;
 
@@ -181,6 +193,7 @@ void dmub_dcn401_backdoor_load_zfb_mode(struct dmub_srv *dmub,
 			DMCUB_REGION3_CW1_TOP_ADDRESS, cw1->region.top,
 			DMCUB_REGION3_CW1_ENABLE, 1);
 
+	/* release DMCUB reset only to prevent premature execution */
 	REG_UPDATE_2(DMCUB_SEC_CNTL, DMCUB_SEC_RESET, 0, DMCUB_MEM_UNIT_ID,
 			0x20);
 }

drivers/gpu/drm/amd/display/dmub/src/dmub_dcn401.h

@@ -169,7 +169,8 @@ struct dmub_srv;
 	DMUB_SF(HOST_INTERRUPT_CSR, HOST_REG_INBOX0_RSP_INT_EN) \
 	DMUB_SF(HOST_INTERRUPT_CSR, HOST_REG_OUTBOX0_RDY_INT_ACK) \
 	DMUB_SF(HOST_INTERRUPT_CSR, HOST_REG_OUTBOX0_RDY_INT_STAT) \
-	DMUB_SF(HOST_INTERRUPT_CSR, HOST_REG_OUTBOX0_RDY_INT_EN)
+	DMUB_SF(HOST_INTERRUPT_CSR, HOST_REG_OUTBOX0_RDY_INT_EN) \
+	DMUB_SF(DMCUB_CNTL, DMCUB_PWAIT_MODE_STATUS)
 
 struct dmub_srv_dcn401_reg_offset {
 #define DMUB_SR(reg) uint32_t reg;