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

[Chen, Guchun]

[Public]

Reviewed-by: Guchun Chen <guchun.c...@amd.com>

Regards,
Guchun

-----Original Message-----
From: Quan, Evan <evan.q...@amd.com> 
Sent: Friday, August 20, 2021 5:01 PM
To: amd-gfx@lists.freedesktop.org
Cc: Deucher, Alexander <alexander.deuc...@amd.com>; Chen, Guchun 
<guchun.c...@amd.com>; Teng, Rui <rui.t...@amd.com>; Quan, Evan 
<evan.q...@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.q...@amd.com>
Reported-by: Rui Teng <rui.t...@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