Re: [PATCH] drm/amdgpu: add post reset IP callback

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On 03/04/2024 09:31, Yu, Lang wrote:
[AMD Official Use Only - General]

-----Original Message-----
From: Sharma, Shashank <Shashank.Sharma@xxxxxxx>
Sent: Wednesday, April 3, 2024 3:19 PM
To: Yu, Lang <Lang.Yu@xxxxxxx>; Christian König
<ckoenig.leichtzumerken@xxxxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian
Subject: Re: [PATCH] drm/amdgpu: add post reset IP callback

Hey Lang,

On 03/04/2024 08:51, Yu, Lang wrote:
[AMD Official Use Only - General]

-----Original Message-----
From: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Sent: Tuesday, April 2, 2024 9:38 PM
To: Yu, Lang <Lang.Yu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian
<Christian.Koenig@xxxxxxx>; Sharma, Shashank
Subject: Re: [PATCH] drm/amdgpu: add post reset IP callback

Am 28.03.24 um 05:40 schrieb Lang Yu:
There are use cases which need full GPU functionality (e.g., VM
update, TLB inavildate) when doing a GPU reset.

Especially, the mes/umsch self tests which help validate the hw
state after hw init like ring/ib tests.
I noted that before but just to repeat it once more: We can't do any
MES or UMSCH validation while doing a GPU reset!
Yes, we can just easily disable it if it doesn't work well.
But it doesn't take too much effort to make it work.
It can expose issues as soon as possible and is useful for debugging
IMO, its not that useful for debugging as well. In case of a problem, It will just
timeout waiting for MES packet write and we will still have to find out the
actual problem which caused MES to go into bad state in the last GPU reset.
The ring and IB tests use some pre-allocated memory we put aside for
the task during driver load and so can execute during GPU reset as well.
If user space can create a VM and allocate memory during GPU reset, it
makes no sense to prevent kernel space from doing that.
I think the objection here is mostly about why to do it at all, when it is not
helpful. It would be just a maintenance overhead.
If you think it is not helpful,  why doing ring/ib tests?
That's because they add value during the bootup, when we know that the HW is being initialized in a controlled/systematic way. But in case of a GPU reset, it could go anyway and could be neither of those.
I don't think such sanity test is not helpful.

I only talk UMSCH test(different with MES test) here,

Your comment above about ring tests talks about both MES/UMSCH self tests, so it attracts attention on both.

If its only about UMSCH tests, I will let someone else to comment on that.

- Shashank

I don't think it has a maintenance overhead.


- Shashank

But for the MES/UMSCH we need a full blown environment with VM and
submission infrastructure and setting that up isn't possible here.
At least for UMSCH test, it only uses VM mapping functionality (if we
can create a VM with cpu update mode, that's enough), it doesn't use
other submission functionality.
It is actually a compute context.


Adding Shashank as well, but I think we should probably just
completely remove those from the kernel.


Add a post reset IP callback to handle such use cases which will be
executed after GPU reset succeeds.

Signed-off-by: Lang Yu <Lang.Yu@xxxxxxx>
    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 24
    drivers/gpu/drm/amd/include/amd_shared.h   |  3 +++
    2 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 12dc71a6b5db..feeab9397aab 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -5556,6 +5556,27 @@ static int
list_head *device_list_handle)
       return ret;

+static int amdgpu_device_ip_post_reset(struct amdgpu_device *adev) {
+    uint32_t i;
+    int r;
+    for (i = 0; i < adev->num_ip_blocks; i++) {
+            if (!adev->ip_blocks[i].status.valid ||
+                !adev->ip_blocks[i].version->funcs->post_reset)
+                    continue;
+            r = adev->ip_blocks[i].version->funcs->post_reset(adev);
+            if (r) {
+                    DRM_ERROR("post reset of IP block <%s>
failed %d\n",
+                              adev->ip_blocks[i].version->funcs->name, r);
+                    return r;
+            }
+    }
+    return r;
     * amdgpu_device_gpu_recover - reset the asic and recover scheduler
@@ -5805,6 +5826,9 @@ int amdgpu_device_gpu_recover(struct
amdgpu_device *adev,

+    if (!r && !job_signaled)
+            r = amdgpu_device_ip_post_reset(adev);
       if (r)
               dev_info(adev->dev, "GPU reset end with ret = %d\n",

diff --git a/drivers/gpu/drm/amd/include/amd_shared.h
index b0a6256e89f4..33ce30a8e3ab 100644
--- a/drivers/gpu/drm/amd/include/amd_shared.h
+++ b/drivers/gpu/drm/amd/include/amd_shared.h
@@ -287,6 +287,7 @@ enum amd_dpm_forced_level;
     * @pre_soft_reset: pre soft reset the IP block
     * @soft_reset: soft reset the IP block
     * @post_soft_reset: post soft reset the IP block
+ * @post_reset: handles IP specific post reset stuff(e.g., self
+ test)
     * @set_clockgating_state: enable/disable cg for the IP block
     * @set_powergating_state: enable/disable pg for the IP block
     * @get_clockgating_state: get current clockgating status @@
+317,13 @@ struct amd_ip_funcs {
       int (*pre_soft_reset)(void *handle);
       int (*soft_reset)(void *handle);
       int (*post_soft_reset)(void *handle);
+    int (*post_reset)(void *handle);
       int (*set_clockgating_state)(void *handle,
                                    enum amd_clockgating_state state);
       int (*set_powergating_state)(void *handle,
                                    enum amd_powergating_state state);
       void (*get_clockgating_state)(void *handle, u64 *flags);

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