[PATCH 03/10] drm/amd/pm: Increase SMC timeout on SI and warn (v3)

[Timur Kristóf]

The SMC can take an excessive amount of time to process some
messages under some conditions.

Background:
Sending a message to the SMC works by writing the message into
the mmSMC_MESSAGE_0 register and its optional parameter into
the mmSMC_SCRATCH0, and then polling mmSMC_RESP_0. Previously
the timeout was AMDGPU_MAX_USEC_TIMEOUT, ie. 100 ms.

Increase the timeout to 200 ms for all messages and to 1 sec for
a few messages which I've observed to be especially slow:
PPSMC_MSG_NoForcedLevel
PPSMC_MSG_SetEnabledLevels
PPSMC_MSG_SetForcedLevels
PPSMC_MSG_DisableULV
PPSMC_MSG_SwitchToSwState

This fixes the following problems on Tahiti when switching
from a lower clock power state to a higher clock state, such
as when DC turns on a display which was previously turned off.

* si_restrict_performance_levels_before_switch would fail
  (if the user previously forced high clocks using sysfs)
* si_set_sw_state would fail (always)

It turns out that both of those failures were SMC timeouts and
that the SMC actually didn't fail or hang, just needs more time
to process those.

Add a warning when there is an SMC timeout to make it easier to
identify this type of problem in the future.

Signed-off-by: Timur Kristóf <timur.kristof at gmail.com>
---
 drivers/gpu/drm/amd/pm/legacy-dpm/si_smc.c | 26 ++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/legacy-dpm/si_smc.c b/drivers/gpu/drm/amd/pm/legacy-dpm/si_smc.c
index 4e65ab9e931c..281a5e377aee 100644
--- a/drivers/gpu/drm/amd/pm/legacy-dpm/si_smc.c
+++ b/drivers/gpu/drm/amd/pm/legacy-dpm/si_smc.c
@@ -172,20 +172,42 @@ PPSMC_Result amdgpu_si_send_msg_to_smc(struct amdgpu_device *adev,
 {
 	u32 tmp;
 	int i;
+	int usec_timeout;
+
+	/* SMC seems to process some messages exceptionally slowly. */
+	switch (msg) {
+	case PPSMC_MSG_NoForcedLevel:
+	case PPSMC_MSG_SetEnabledLevels:
+	case PPSMC_MSG_SetForcedLevels:
+	case PPSMC_MSG_DisableULV:
+	case PPSMC_MSG_SwitchToSwState:
+		usec_timeout = 1000000; /* 1 sec */
+		break;
+	default:
+		usec_timeout = 200000; /* 200 ms */
+		break;
+	}
 
 	if (!amdgpu_si_is_smc_running(adev))
 		return PPSMC_Result_Failed;
 
 	WREG32(mmSMC_MESSAGE_0, msg);
 
-	for (i = 0; i < adev->usec_timeout; i++) {
+	for (i = 0; i < usec_timeout; i++) {
 		tmp = RREG32(mmSMC_RESP_0);
 		if (tmp != 0)
 			break;
 		udelay(1);
 	}
 
-	return (PPSMC_Result)RREG32(mmSMC_RESP_0);
+	tmp = RREG32(mmSMC_RESP_0);
+	if (tmp == 0) {
+		drm_warn(adev_to_drm(adev),
+			"%s timeout on message: %x (SMC_SCRATCH0: %x)\n",
+			__func__, msg, RREG32(mmSMC_SCRATCH0));
+	}
+
+	return (PPSMC_Result)tmp;
 }
 
 PPSMC_Result amdgpu_si_wait_for_smc_inactive(struct amdgpu_device *adev)
-- 
2.51.0