Re: [PATCH] drm/i915: Add debug module option for VTd validation

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 01 Apr 2014, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> VTd has a few too many "outright disable the damn thing" workarounds
> accumulated and for validation we want a simple knob to make sure we
> disable them all.
>
> Since this is for bdw+ validation and atm we don't have any
> workarounds for bdw this option currently does nothing. So currently
> this is just a placeholder to make sure reality will match with the
> documented process for our validation people.
>
> v2: Fix up param description (Jani).
>
> v3: Actually git add ...

*rolls eyes* ;)

I'm really sorry I just spotted that one param desc and failed to do any
proper review. So here's some bikeshedding.

>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_drv.h    | 1 +
>  drivers/gpu/drm/i915/i915_params.c | 4 ++++
>  2 files changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index ff02225d5edd..610ff70f8609 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1925,6 +1925,7 @@ struct i915_params {
>  	bool prefault_disable;
>  	bool reset;
>  	bool disable_display;
> +	bool disable_vtd_wa;
>  };
>  extern struct i915_params i915 __read_mostly;
>  
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index e1027cc5f0ee..d05a2afa17dc 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -47,6 +47,7 @@ struct i915_params i915 __read_mostly = {
>  	.invert_brightness = 0,
>  	.disable_display = 0,
>  	.enable_cmd_parser = 1,
> +	.disable_vtd_wa = 0,

Gringe at initializing bools with ints.

>  };
>  
>  module_param_named(modeset, i915.modeset, int, 0400);
> @@ -149,6 +150,9 @@ MODULE_PARM_DESC(invert_brightness,
>  module_param_named(disable_display, i915.disable_display, bool, 0600);
>  MODULE_PARM_DESC(disable_display, "Disable display (default: false)");
>  
> +module_param_named(disable_vtd_wa, i915.disable_vtd_wa, bool, 0600);
> +MODULE_PARM_DESC(disable_vtd_wa, "Disable all VT-d workarounds (default: false)");
> +

Why negative? Why not enable_vtd_wa defaulting to true? The disable will
lead to code like:

	if (!i915.disable_vtd_wa)

instead of

	if (i915.enable_vtd_wa)


Regardless of the bikeshedding, it's

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


>  module_param_named(enable_cmd_parser, i915.enable_cmd_parser, int, 0600);
>  MODULE_PARM_DESC(enable_cmd_parser,
>  		 "Enable command parsing (1=enabled [default], 0=disabled)");
> -- 
> 1.8.5.2
>

-- 
Jani Nikula, Intel Open Source Technology Center