Re: [PATCH] drm/i915: Don't try to handle GuC when GuC is not supported.

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Qua, 2016-09-21 às 11:22 -0700, Rodrigo Vivi escreveu:
> Avoid any kind of GuC handling if GuC is not supported
> on a giving platform.
> 
> Besides being useless handling, our driver needs
> to be smarter than the user trying to use an invalid paramenter.

So the problem is when a platform doesn't support guc and the user
passes i915.enable_guc_something=1, right?

> 
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> Cc: Christophe Prigent <christophe.prigent@intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97573
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_guc_loader.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c
> b/drivers/gpu/drm/i915/intel_guc_loader.c
> index 6fd39ef..da0f5ed 100644
> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
> @@ -720,6 +720,13 @@ void intel_guc_init(struct drm_device *dev)
>  	struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
>  	const char *fw_path;
>  
> +	if (!HAS_GUC(dev)) {
> +		i915.enable_guc_loading = 0;
> +		i915.enable_guc_submission = 0;
> +		fw_path = NULL;
> +		return;
> +	}

Instead of this, how about we just patch the code below with:

if (!HAS_GUC(dev_priv)) {
	i915.enable_guc_loading = 0;
	i915.enable_guc_submission = 0;
} else {
	/* A negative value means "use platform default" */
	if (i915.enable_guc_loading < 0)
		i915.enable_guc_loading = HAS_GUC_UCODE(dev_priv);
	if (i915.enable_guc_submission < 0)
		i915.enable_guc_submission = HAS_GUC_SCHED(dev_priv);
}

Or we could even go with our current "design pattern" and create
intel_sanitize_guc_options().

This way we'll be able to avoid adding a second failure code path,
since we already have one for platforms with guc but options disabled.


> +
>  	/* A negative value means "use platform default" */
>  	if (i915.enable_guc_loading < 0)
>  		i915.enable_guc_loading = HAS_GUC_UCODE(dev);
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