[PATCH] drm/amd/pm: a quick fix for "divided by zero" error

[Chen, Guchun]

[Public]

Reviewed-by: Guchun Chen <guchun.chen at amd.com>

Regards,
Guchun

-----Original Message-----
From: Quan, Evan <Evan.Quan at amd.com> 
Sent: Friday, August 20, 2021 5:01 PM
To: amd-gfx at lists.freedesktop.org
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Chen, Guchun <Guchun.Chen at amd.com>; Teng, Rui <Rui.Teng at amd.com>; Quan, Evan <Evan.Quan at amd.com>
Subject: [PATCH] drm/amd/pm: a quick fix for "divided by zero" error

Considering Arcturus is a dedicated ASIC for computing, it will be more proper to drop the support for fan speed reading and setting. That's on the TODO list.

Change-Id: Id83a7a88f26644ba66c4fd15034b4fc861cc6901
Signed-off-by: Evan Quan <evan.quan at amd.com>
Reported-by: Rui Teng <rui.teng at amd.com>
---
 .../gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c | 20 ++++++++++++-------
 .../gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c    |  9 +++++++--
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
index fbf71fc92b16..273df66cac14 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
@@ -1227,8 +1227,12 @@ static int arcturus_get_fan_speed_rpm(struct smu_context *smu,
 
 		tmp64 = (uint64_t)crystal_clock_freq * 60 * 10000;
 		tach_status = RREG32_SOC15(THM, 0, mmCG_TACH_STATUS_ARCT);
-		do_div(tmp64, tach_status);
-		*speed = (uint32_t)tmp64;
+		if (tach_status) {
+			do_div(tmp64, tach_status);
+			*speed = (uint32_t)tmp64;
+		} else {
+			*speed = 0;
+		}
 
 		break;
 	}
@@ -1303,12 +1307,14 @@ static int arcturus_get_fan_speed_pwm(struct smu_context *smu,
 				CG_FDO_CTRL1, FMAX_DUTY100);
 	duty = REG_GET_FIELD(RREG32_SOC15(THM, 0, mmCG_THERMAL_STATUS_ARCT),
 				CG_THERMAL_STATUS, FDO_PWM_DUTY);
-	if (!duty100)
-		return -EINVAL;
 
-	tmp64 = (uint64_t)duty * 255;
-	do_div(tmp64, duty100);
-	*speed = MIN((uint32_t)tmp64, 255);
+	if (duty100) {
+		tmp64 = (uint64_t)duty * 255;
+		do_div(tmp64, duty100);
+		*speed = MIN((uint32_t)tmp64, 255);
+	} else {
+		*speed = 0;
+	}
 
 	return 0;
 }
diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
index 01b9653c39c7..87b055466a33 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c
@@ -1306,8 +1306,13 @@ int smu_v11_0_get_fan_speed_rpm(struct smu_context *smu,
 	tmp64 = (uint64_t)crystal_clock_freq * 60 * 10000;
 
 	tach_status = RREG32_SOC15(THM, 0, mmCG_TACH_STATUS);
-	do_div(tmp64, tach_status);
-	*speed = (uint32_t)tmp64;
+	if (tach_status) {
+		do_div(tmp64, tach_status);
+		*speed = (uint32_t)tmp64;
+	} else {
+		dev_warn_once(adev->dev, "Got zero output on CG_TACH_STATUS reading!\n");
+		*speed = 0;
+	}
 
 	return 0;
 }
--
2.29.0