Re: [PATCH v3 1/2] drm/amdgpu: add debugfs for reset registers list

["Somalapuram, Amaranath" <asomalap@xxxxxxx>]

On 2/14/2022 2:59 PM, Christian König wrote:
> Am 14.02.22 um 10:16 schrieb Somalapuram Amaranath:
> > List of register populated for dump collection during the GPU reset.
> >
> > Signed-off-by: Somalapuram Amaranath <Amaranath.Somalapuram@xxxxxxx>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  4 ++
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 80 +++++++++++++++++++++
> >   2 files changed, 84 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > index b85b67a88a3d..2e8c2318276d 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> > @@ -1097,6 +1097,10 @@ 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;
> >   };
> >     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..6d49bed5b761 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > @@ -1609,6 +1609,84 @@ 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;
> > +    int i, r, len;
> > +
> > +    if (adev->n_regs == 0)
> > +        return 0;
> > +
> > +    reg_offset = kmalloc((adev->n_regs * 11) + 1, GFP_KERNEL);
> > +    memset(reg_offset,  0, (adev->n_regs * 11) + 1);
> > +
> > +    for (i = 0; i < adev->n_regs; i++)
> > +        sprintf(reg_offset + strlen(reg_offset), "0x%x ", 
> > adev->reset_dump_reg_list[i]);
> > +
> > +    sprintf(reg_offset + strlen(reg_offset), "\n");
> > +    len = strlen(reg_offset);
> > +
> > +    if (*pos >= len)
> > +        return 0;
> > +
> > +    r = copy_to_user(buf, reg_offset, len);
>
> Maybe better copy that to userspace one register at a time. This is 
> not performance critical in any way.
>
> Same for the write function.
>
> Regards,
> Christian.
I tried to push all list of register in one go, so that the list can be 
overwritten/updated (every write makes new list)
if we add one register at a time from user-space the design will change 
to appending the list and cant be edited or updated, it should be OK ?
and don't see much use of **_read api (as we can see the list in trace) 
i will remove it (debugfs interface will change from string to uint32_t )!?

Regards,
S.Amarnath
> > +    *pos += len - r;
> > +    kfree(reg_offset);
> > +
> > +    return len - r;
> > +}
> > +
> > +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;
> > +    int ret, i = 0;
> > +
> > +    reg_offset = kmalloc(size, GFP_KERNEL);
> > +    memset(reg_offset,  0, size);
> > +    ret = copy_from_user(reg_offset, buf, size);
> > +
> > +    if (ret)
> > +        return -EFAULT;
> > +
> > +    if (adev->n_regs > 0) {
> > +        adev->n_regs = 0;
> > +        kfree(adev->reset_dump_reg_list);
> > +        adev->reset_dump_reg_list = NULL;
> > +    }
> > +
> > +    while ((reg = strsep(&reg_offset, " ")) != NULL) {
> > +        adev->reset_dump_reg_list =  krealloc_array(
> > +                        adev->reset_dump_reg_list, 1,
> > +                        sizeof(uint32_t), GFP_KERNEL);
> > +        ret  = kstrtouint(reg, 16, &adev->reset_dump_reg_list[i]);
> > +
> > +        if (ret) {
> > +            kfree(adev->reset_dump_reg_list);
> > +            kfree(reg_offset);
> > +            adev->reset_dump_reg_list = NULL;
> > +            return -EINVAL;
> > +        }
> > +
> > +        i++;
> > +    }
> > +
> > +    adev->n_regs = i;
> > +    kfree(reg_offset);
> > +
> > +    return size;
> > +}
> > +
> > +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;
> > @@ -1672,6 +1750,8 @@ 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;