Re: [PATCH v4 1/2] drm/amdgpu: add debugfs for reset registers list

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

On 2/15/2022 3:46 PM, Christian König wrote:
> Am 15.02.22 um 11:12 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 | 89 +++++++++++++++++++++
> >   2 files changed, 93 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..edcb032bc1f3 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > @@ -1609,6 +1609,93 @@ 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 (adev->n_regs == 0)
> > +        return 0;
> > +
> > +    for (i = 0; i < adev->n_regs; i++) {
> > +        memset(reg_offset,  0, 11);
> > +        sprintf(reg_offset + strlen(reg_offset),
>
> That here looks odd, probably just a leftover from the older code.
My mistake leftover code.

let me try to remove memset() also.

> Without it you can also drop the memset().
>
> > +                "0x%x ", adev->reset_dump_reg_list[i]);
> > +        r = copy_to_user(buf + len, reg_offset, strlen(reg_offset));
>
> Whenever copy_to_user() returns a nonzero value the best practice is 
> to return -EFAULT.
agreed.
> > +        len += strlen(reg_offset);
> > +    }
> > +
> > +    r = copy_to_user(buf + len, "\n", 1);
>
> Same here.
agreed.
> > +    len++;
> > +
> > +    if (*pos >= len)
> > +        return 0;
>
> What is that good for?
If i don't have this condition read operation will be infinite loop and 
data keeps repeating.

I am not sure why !. maybe i need to set something while write operation.

> Regards,
> Christian.
>
> > +
> > +    *pos += len - r;
> > +
> > +    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];
> > +    int ret, i = 0, len = 0;
> > +
> > +    reg_offset = reg_temp;
> > +    memset(reg_offset,  0, 11);
> > +    ret = copy_from_user(reg_offset, buf, 11);
> > +
> > +    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) && len < size) {
> > +        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);
> > +            adev->reset_dump_reg_list = NULL;
> > +            return -EINVAL;
> > +        }
> > +
> > +        len += strlen(reg) + 1;
> > +        reg_offset = reg_temp;
> > +        memset(reg_offset,  0, 11);
> > +        ret = copy_from_user(reg_offset, buf + len, 11);
> > +
> > +        if (ret) {
> > +            kfree(adev->reset_dump_reg_list);
> > +            adev->reset_dump_reg_list = NULL;
> > +            return -EFAULT;
> > +        }
> > +
> > +        i++;
> > +    }
> > +
> > +    adev->n_regs = i;
> > +
> > +    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 +1759,8 @@ 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;