Re: [PATCH v6 1/2] drm/xe: add a new debugfs file - mmio

["Summers, Stuart" <stuart.summers@intel.com>]

On Wed, 2024-01-31 at 21:59 +0200, Koby Elbaz wrote:
> Now that the former mmio handlers are fully removed, this
> debugfs file will be used for mmio access (read/write)
> through the debugfs ioctl file operation.

Sorry I don't know the history here of v0-v5, but one question, with
igt-gpu-tools/tools/intel_reg we can read and write MMIO registers
without needing to have the driver loaded at all (i.e. straight through
the BARs). Why do we want to also put this capability in the xe debugfs
then?

Thanks,
Stuart

> 
> Signed-off-by: Koby Elbaz <kelbaz@habana.ai>
> ---
>  drivers/gpu/drm/xe/xe_debugfs.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_debugfs.c
> b/drivers/gpu/drm/xe/xe_debugfs.c
> index 01db5b27bec5..21b2257aa3a8 100644
> --- a/drivers/gpu/drm/xe/xe_debugfs.c
> +++ b/drivers/gpu/drm/xe/xe_debugfs.c
> @@ -98,12 +98,22 @@ static int forcewake_release(struct inode *inode,
> struct file *file)
>         return 0;
>  }
>  
> +static long xe_debugfs_mmio_ioctl(struct file *f, unsigned int cmd,
> unsigned long arg)
> +{
> +       return 0;
> +}
> +
>  static const struct file_operations forcewake_all_fops = {
>         .owner = THIS_MODULE,
>         .open = forcewake_open,
>         .release = forcewake_release,
>  };
>  
> +static const struct file_operations mmio_fops = {
> +       .owner = THIS_MODULE,
> +       .unlocked_ioctl = xe_debugfs_mmio_ioctl,
> +};
> +
>  void xe_debugfs_register(struct xe_device *xe)
>  {
>         struct ttm_device *bdev = &xe->ttm;
> @@ -142,6 +152,8 @@ void xe_debugfs_register(struct xe_device *xe)
>         for_each_gt(gt, xe, id)
>                 xe_gt_debugfs_register(gt);
>  
> +       debugfs_create_file("mmio", 0644, root, xe, &mmio_fops);
> +
>  #ifdef CONFIG_FAULT_INJECTION
>         fault_create_debugfs_attr("fail_gt_reset", root,
> &gt_reset_failure);
>  #endif