Re: [PATCH v6 1/2] drm/amdgpu: add debugfs for reset registers list

["Christian König" <christian.koenig@amd.com>]

Am 16.02.22 um 11:43 schrieb Lazar, Lijo:
>
>
> On 2/16/2022 4:04 PM, Somalapuram, Amaranath wrote:
>>
>> On 2/16/2022 3:45 PM, Lazar, Lijo wrote:
>>>
>>>
>>> On 2/16/2022 3:19 PM, Somalapuram Amaranath wrote:
>>>> List of register populated for dump collection during the GPU reset.
>>>>
>>>> Signed-off-by: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
>>>> ---
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  5 ++
>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 95 
>>>> +++++++++++++++++++++
>>>>   2 files changed, 100 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> index b85b67a88a3d..57965316873b 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> @@ -1097,6 +1097,11 @@ struct amdgpu_device {
>>>>         struct amdgpu_reset_control     *reset_cntl;
>>>>       uint32_t ip_versions[HW_ID_MAX][HWIP_MAX_INSTANCE];
>>>> +
>>>> +    /* reset dump register */
>>>> +    uint32_t            *reset_dump_reg_list;
>>>> +    int                             n_regs;
>>>> +    struct mutex            reset_dump_mutex;
>>>>   };
>>>>     static inline struct amdgpu_device *drm_to_adev(struct 
>>>> drm_device *ddev)
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c 
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>> index 164d6a9e9fbb..faf985c7cb93 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>>>> @@ -1609,6 +1609,98 @@ DEFINE_DEBUGFS_ATTRIBUTE(fops_ib_preempt, NULL,
>>>>   DEFINE_DEBUGFS_ATTRIBUTE(fops_sclk_set, NULL,
>>>>               amdgpu_debugfs_sclk_set, "%llu\n");
>>>>   +static ssize_t amdgpu_reset_dump_register_list_read(struct file *f,
>>>> +                char __user *buf, size_t size, loff_t *pos)
>>>> +{
>>>> +    struct amdgpu_device *adev = (struct amdgpu_device 
>>>> *)file_inode(f)->i_private;
>>>> +    char reg_offset[11];
>>>> +    int i, r, len = 0;
>>>> +
>>>> +    if (*pos)
>>>> +        return 0;
>>>> +
>>>> +    if (adev->n_regs == 0)
>>>> +        return 0;
>>>> +
>>>> +    for (i = 0; i < adev->n_regs; i++) {
>>>> +        sprintf(reg_offset, "0x%x ", adev->reset_dump_reg_list[i]);
>>>> +        r = copy_to_user(buf + len, reg_offset, strlen(reg_offset));
>>>> +
>>>> +        if (r)
>>>> +            return -EFAULT;
>>>> +
>>>> +        len += strlen(reg_offset);
>>>> +    }
>>>> +
>>>> +    r = copy_to_user(buf + len, "\n", 1);
>>>> +
>>>> +    if (r)
>>>> +        return -EFAULT;
>>>> +
>>>> +    len++;
>>>> +    *pos += len;
>>>> +
>>>> +    return len;
>>>> +}
>>>> +
>>>> +static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
>>>> +            const char __user *buf, size_t size, loff_t *pos)
>>>> +{
>>>> +    struct amdgpu_device *adev = (struct amdgpu_device 
>>>> *)file_inode(f)->i_private;
>>>> +    char *reg_offset, *reg, reg_temp[11];
>>>> +    static int alloc_count;
>>>
>>> This being static what happens when it is called on a second device?

Good point. I've totally missed that.

>>>
>>> Thanks,
>>> Lijo
>>>
>> I tried to avoid adding to adev. It wont work for multiple devices.
>
> Hmm.This is not friendly for single device also. Some one could just 
> parse a text file of reg offsets and do
>     sudo echo offset > file
>
> This will overwrite whatever is there. Instead you may define a syntax 
> like
>     sudo echo 0x000 > file =>  Clears all
>     sudo echo offset > file => Append to the existing set.
>
> Taking all offsets in one go may not be needed.

Yes, completely agree. Now that you mention it the code here is severely 
broken in quite a number of ways, but see below.

>
> Thanks,
> Lijo
>
>>>> +    int ret, i = 0, len = 0;
>>>> +
>>>> +    do {
>>>> +        reg_offset = reg_temp;
>>>> +        memset(reg_offset,  0, 11);
>>>> +        ret = copy_from_user(reg_offset, buf + len, min(11, 
>>>> ((int)size-len)));
>>>> +
>>>> +        if (ret)
>>>> +            goto failed;
>>>> +
>>>> +        reg = strsep(&reg_offset, " ");
>>>> +
>>>> +        if (alloc_count <= i) {

The alloc_count variable and this check is completely unnecessary.

>>>> + adev->reset_dump_reg_list =  krealloc_array(
>>>> +                            adev->reset_dump_reg_list, 1,

The memory management knows internally how much memory is allocated and 
when the buffer needs to be re-allocated for grow.

So all you need to do is is "array = krealloc_array(array, i, 
sizeof(*array), GFP_KERNEL);"

Regards,
Christian.


>>>> + sizeof(uint32_t), GFP_KERNEL);
>>>> +            alloc_count++;
>>>> +        }
>>>> +
>>>> +        ret = kstrtouint(reg, 16, &adev->reset_dump_reg_list[i]);
>>>> +
>>>> +        if (ret)
>>>> +            goto failed;
>>>> +
>>>> +        len += strlen(reg) + 1;
>>>> +        i++;
>>>> +
>>>> +    } while (len < size);
>>>> +
>>>> +    adev->n_regs = i;
>>>> +
>>>> +    return size;
>>>> +
>>>> +failed:
>>>> +    mutex_lock(&adev->reset_dump_mutex);
>>>> +    kfree(adev->reset_dump_reg_list);
>>>> +    adev->reset_dump_reg_list = NULL;
>>>> +    alloc_count = 0;
>>>> +    adev->n_regs = 0;
>>>> +    mutex_unlock(&adev->reset_dump_mutex);
>>>> +    return -EFAULT;
>>>> +}
>>>> +
>>>> +
>>>> +
>>>> +static const struct file_operations 
>>>> amdgpu_reset_dump_register_list = {
>>>> +    .owner = THIS_MODULE,
>>>> +    .read = amdgpu_reset_dump_register_list_read,
>>>> +    .write = amdgpu_reset_dump_register_list_write,
>>>> +    .llseek = default_llseek
>>>> +};
>>>> +
>>>>   int amdgpu_debugfs_init(struct amdgpu_device *adev)
>>>>   {
>>>>       struct dentry *root = adev_to_drm(adev)->primary->debugfs_root;
>>>> @@ -1618,6 +1710,7 @@ int amdgpu_debugfs_init(struct amdgpu_device 
>>>> *adev)
>>>>       if (!debugfs_initialized())
>>>>           return 0;
>>>>   +    mutex_init(&adev->reset_dump_mutex);
>>>>       ent = debugfs_create_file("amdgpu_preempt_ib", 0600, root, adev,
>>>>                     &fops_ib_preempt);
>>>>       if (IS_ERR(ent)) {
>>>> @@ -1672,6 +1765,8 @@ int amdgpu_debugfs_init(struct amdgpu_device 
>>>> *adev)
>>>>                   &amdgpu_debugfs_test_ib_fops);
>>>>       debugfs_create_file("amdgpu_vm_info", 0444, root, adev,
>>>>                   &amdgpu_debugfs_vm_info_fops);
>>>> +    debugfs_create_file("amdgpu_reset_dump_register_list", 0644, 
>>>> root, adev,
>>>> +                &amdgpu_reset_dump_register_list);
>>>>         adev->debugfs_vbios_blob.data = adev->bios;
>>>>       adev->debugfs_vbios_blob.size = adev->bios_size;
>>>>