[PATCH 2/2] drm/amdgpu: add support for SMU debug option
Christian König
christian.koenig at amd.com
Fri Dec 10 07:04:03 UTC 2021
Am 10.12.21 um 04:21 schrieb Lang Yu:
> On 12/10/ , Quan, Evan wrote:
>> [AMD Official Use Only]
>>
>>
>>
>>> -----Original Message-----
>>> From: Yu, Lang <Lang.Yu at amd.com>
>>> Sent: Friday, December 10, 2021 10:34 AM
>>> To: Quan, Evan <Evan.Quan at amd.com>
>>> Cc: amd-gfx at lists.freedesktop.org; Grodzovsky, Andrey
>>> <Andrey.Grodzovsky at amd.com>; Lazar, Lijo <Lijo.Lazar at amd.com>; Huang,
>>> Ray <Ray.Huang at amd.com>; Deucher, Alexander
>>> <Alexander.Deucher at amd.com>; Koenig, Christian
>>> <Christian.Koenig at amd.com>
>>> Subject: Re: [PATCH 2/2] drm/amdgpu: add support for SMU debug option
>>>
>>> On 12/10/ , Quan, Evan wrote:
>>>> [AMD Official Use Only]
>>>>
>>>>
>>>>
>>>>> -----Original Message-----
>>>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>>>>> Lang Yu
>>>>> Sent: Thursday, December 9, 2021 4:49 PM
>>>>> To: amd-gfx at lists.freedesktop.org
>>>>> Cc: Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com>; Lazar, Lijo
>>>>> <Lijo.Lazar at amd.com>; Huang, Ray <Ray.Huang at amd.com>; Deucher,
>>>>> Alexander <Alexander.Deucher at amd.com>; Yu, Lang
>>> <Lang.Yu at amd.com>;
>>>>> Koenig, Christian <Christian.Koenig at amd.com>
>>>>> Subject: [PATCH 2/2] drm/amdgpu: add support for SMU debug option
>>>>>
>>>>> SMU firmware guys expect the driver maintains error context and
>>>>> doesn't interact with SMU any more when SMU errors occurred.
>>>>> That will aid in debugging SMU firmware issues.
>>>>>
>>>>> Add SMU debug option support for this request, it can be enabled or
>>>>> disabled via amdgpu_smu_debug debugfs file.
>>>>> When enabled, it brings hardware to a kind of halt state so that no
>>>>> one can touch it any more in the envent of SMU errors.
>>>>>
>>>>> Currently, dirver interacts with SMU via sending messages.
>>>>> And threre are three ways to sending messages to SMU.
>>>>> Handle them respectively as following:
>>>>>
>>>>> 1, smu_cmn_send_smc_msg_with_param() for normal timeout cases
>>>>>
>>>>> Halt on any error.
>>>>>
>>>>> 2,
>>> smu_cmn_send_msg_without_waiting()/smu_cmn_wait_for_response()
>>>>> for longer timeout cases
>>>>>
>>>>> Halt on errors apart from ETIME. Otherwise this way won't work.
>>>>>
>>>>> 3, smu_cmn_send_msg_without_waiting() for no waiting cases
>>>>>
>>>>> Halt on errors apart from ETIME. Otherwise second way won't work.
>>>>>
>>>>> After halting, use BUG() to explicitly notify users.
>>>>>
>>>>> == Command Guide ==
>>>>>
>>>>> 1, enable SMU debug option
>>>>>
>>>>> # echo 1 > /sys/kernel/debug/dri/0/amdgpu_smu_debug
>>>>>
>>>>> 2, disable SMU debug option
>>>>>
>>>>> # echo 0 > /sys/kernel/debug/dri/0/amdgpu_smu_debug
>>>>>
>>>>> v4:
>>>>> - Set to halt state instead of a simple hang.(Christian)
>>>>>
>>>>> v3:
>>>>> - Use debugfs_create_bool().(Christian)
>>>>> - Put variable into smu_context struct.
>>>>> - Don't resend command when timeout.
>>>>>
>>>>> v2:
>>>>> - Resend command when timeout.(Lijo)
>>>>> - Use debugfs file instead of module parameter.
>>>>>
>>>>> Signed-off-by: Lang Yu <lang.yu at amd.com>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 3 +++
>>>>> drivers/gpu/drm/amd/pm/inc/amdgpu_smu.h | 5 +++++
>>>>> drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c | 20
>>>>> +++++++++++++++++++-
>>>>> 3 files changed, 27 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>>> index 164d6a9e9fbb..86cd888c7822 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>>> @@ -1618,6 +1618,9 @@ int amdgpu_debugfs_init(struct
>>> amdgpu_device
>>>>> *adev)
>>>>> if (!debugfs_initialized())
>>>>> return 0;
>>>>>
>>>>> + debugfs_create_bool("amdgpu_smu_debug", 0600, root,
>>>>> + &adev->smu.smu_debug_mode);
>>>>> +
>>>>> ent = debugfs_create_file("amdgpu_preempt_ib", 0600, root, adev,
>>>>> &fops_ib_preempt);
>>>>> if (IS_ERR(ent)) {
>>>>> diff --git a/drivers/gpu/drm/amd/pm/inc/amdgpu_smu.h
>>>>> b/drivers/gpu/drm/amd/pm/inc/amdgpu_smu.h
>>>>> index f738f7dc20c9..50dbf5594a9d 100644
>>>>> --- a/drivers/gpu/drm/amd/pm/inc/amdgpu_smu.h
>>>>> +++ b/drivers/gpu/drm/amd/pm/inc/amdgpu_smu.h
>>>>> @@ -569,6 +569,11 @@ struct smu_context
>>>>> struct smu_user_dpm_profile user_dpm_profile;
>>>>>
>>>>> struct stb_context stb_context;
>>>>> + /*
>>>>> + * When enabled, it makes SMU errors fatal.
>>>>> + * (0 = disabled (default), 1 = enabled)
>>>>> + */
>>>>> + bool smu_debug_mode;
>>>> [Quan, Evan] Can you expand this to bit mask(as ppfeaturemask)? So that
>>> in future we can add support for other debug features.
>>>>> };
>>> OK.
>>>
>>>>> struct i2c_adapter;
>>>>> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
>>>>> b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
>>>>> index 048ca1673863..84016d22c075 100644
>>>>> --- a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
>>>>> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
>>>>> @@ -272,6 +272,11 @@ int smu_cmn_send_msg_without_waiting(struct
>>>>> smu_context *smu,
>>>>> __smu_cmn_send_msg(smu, msg_index, param);
>>>>> res = 0;
>>>>> Out:
>>>>> + if (unlikely(smu->smu_debug_mode) && res && (res != -ETIME)) {
>>>>> + amdgpu_device_halt(smu->adev);
>>>>> + BUG();
>>>> [Quan, Evan] I agree amdgpu_device_halt() is a good idea. Christian and
>>> Andrey can share you more insights about that.
>>>> Do we still need the "BUG()" then?
>>> The BUG() is used to explicitly notify users something went wrong.
>>> Otherwise userspace may not know immediately.
>>> FW guys request this in ticket.
>> [Quan, Evan] Won't drm_dev_unplug() and pci_disable_device() used in amdgpu_device_halt throw some errors(on user's further attempt to communicate with our driver)?
>> Also if the purpose is to raise user's concern, WARN() may be a more gentle way?
> From my testing and observation, it depends on what the driver will do next.
> Probably trigger a page fault. If we don't connect a monitor but SSH access.
> We don't know what happended until something like a page fault is triggered.
>
> But here what I want to do is throwing the error immediately to userspace.
> If using WARN(), the user need to poll dmesg to see if something went wrong.
I agree with Evan as well. Please use WARN() or WARN_ON() here instead.
BUG() and BUG_ON() is only allowed when you prevent further data
corruption by intentionally crashing the kernel thread. But that is
really invasive because for example locks are not necessarily dropped
and so can crash the whole system.
Regards,
Christian.
>
> Regards,
> Lang
>
>> BR
>> Evan
>>> Regards,
>>> Lang
>>>
>>>> BR
>>>> Evan
>>>>> + }
>>>>> +
>>>>> return res;
>>>>> }
>>>>>
>>>>> @@ -288,9 +293,17 @@ int smu_cmn_send_msg_without_waiting(struct
>>>>> smu_context *smu,
>>>>> int smu_cmn_wait_for_response(struct smu_context *smu) {
>>>>> u32 reg;
>>>>> + int res;
>>>>>
>>>>> reg = __smu_cmn_poll_stat(smu);
>>>>> - return __smu_cmn_reg2errno(smu, reg);
>>>>> + res = __smu_cmn_reg2errno(smu, reg);
>>>>> +
>>>>> + if (unlikely(smu->smu_debug_mode) && res && (res != -ETIME)) {
>>>>> + amdgpu_device_halt(smu->adev);
>>>>> + BUG();
>>>>> + }
>>>>> +
>>>>> + return res;
>>>>> }
>>>>>
>>>>> /**
>>>>> @@ -357,6 +370,11 @@ int
>>> smu_cmn_send_smc_msg_with_param(struct
>>>>> smu_context *smu,
>>>>> if (read_arg)
>>>>> smu_cmn_read_arg(smu, read_arg);
>>>>> Out:
>>>>> + if (unlikely(smu->smu_debug_mode) && res) {
>>>>> + amdgpu_device_halt(smu->adev);
>>>>> + BUG();
>>>>> + }
>>>>> +
>>>>> mutex_unlock(&smu->message_lock);
>>>>> return res;
>>>>> }
>>>>> --
>>>>> 2.25.1
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