[PATCH] drm/ast: Fixed reboot test may cause system hanged

[Benjamin Herrenschmidt]

On Wed, 2018-04-11 at 09:27 +0800, Y.C. Chen wrote:
> index dac3558..82a2687 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -131,8 +131,8 @@ static int ast_detect_chip(struct drm_device *dev, bool *need_post)
>  
>  
>         /* Enable extended register access */
> -       ast_enable_mmio(dev);
>         ast_open_key(ast);
> +       ast_enable_mmio(dev);

Why that change ? The documentation doesn't really specify what the
"password" register is about. What does it "open" ?

I'm being a bit paranoid because we had issues with earlier drivers
(before some of the latest changes to that code) where occasionally
on boot, the chip wouldn't respond to an MMIO to one of the VGA
registers, causing an EEH error which crashes on boot.

So I want to make sure I understand what the changes precisely do.

Cheers,
Ben.