[Intel-gfx] [PATCH 2/2] drm/i915: Sanitize enable_guc properly on non-guc platforms

[Michal Wajdeczko]

On Tue, 17 Jul 2018 16:22:01 +0200, Ville Syrjälä  
<ville.syrjala at linux.intel.com> wrote:

> On Tue, Jul 17, 2018 at 03:26:18PM +0200, Michal Wajdeczko wrote:
>> On Tue, 17 Jul 2018 14:53:20 +0200, Ville Syrjala
>> <ville.syrjala at linux.intel.com> wrote:
>>
>> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> >
>> > If there's no guc don't try to initialize it even if the user asked  
>> for
>> > it.
>> >
>> > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
>> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/intel_uc.c | 5 +++++
>> >  1 file changed, 5 insertions(+)
>> >
>> > diff --git a/drivers/gpu/drm/i915/intel_uc.c
>> > b/drivers/gpu/drm/i915/intel_uc.c
>> > index 7c95697e1a35..2765808b01e0 100644
>> > --- a/drivers/gpu/drm/i915/intel_uc.c
>> > +++ b/drivers/gpu/drm/i915/intel_uc.c
>> > @@ -106,6 +106,11 @@ static void sanitize_options_early(struct
>> > drm_i915_private *i915)
>> >  	struct intel_uc_fw *guc_fw = &i915->guc.fw;
>> >  	struct intel_uc_fw *huc_fw = &i915->huc.fw;
>> > +	if (!HAS_GUC(i915)) {
>> > +		i915_modparams.enable_guc = 0;
>> > +		return;
>> > +	}
>> > +
>>
>> This will silently switch from user requested GuC-submission to
>> execlist-mode which we wanted to stop.
>>
>> If user don't know what is available on given platform then auto(-1)
>> mode should be used instead. If user has decided to explicitly specify
>> invalid enable_guc !0 mode on non-GuC platform why do we want to ignore
>> that and continue as nothing happened?
>
> If we want to fail then we should at least fail nicer and tell the user
> they're trying something that's not possible.
>

One should see this warning message:

	DRM_WARN("Incompatible option detected: %s=%d, %s!\n",
		 "enable_guc", i915_modparams.enable_guc,
		 !HAS_GUC(i915) ? "no GuC hardware" :
				  "no GuC firmware");

and after we finally fix -EIO support it will be followed by:

	"Failed to initialize GPU, declaring it wedged!\n"

Michal