Re: [PATCH 3/3] drm/i915: Use ELK stolen memory reserved detection for ILK

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

Em Qui, 2017-11-02 às 17:17 +0200, Ville Syrjala escreveu:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> While I have no solid proof that ILK follows the ELK path when it
> comes to the stolen memory reserved area, there are some hints that
> it might be the case. Unfortunately my ILK doesn't have this enabled,
> and no way to enable it via the BIOS it seems.
> 
> So let's have ILK use the ELK code path, and let's toss in a WARN
> into the code to see if we catch anyone with an ILK that has this
> enabled to further analyze the situation.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c
> b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 4f9377b5f4ae..1877ae9a1d9b 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -300,6 +300,12 @@ static void g4x_get_stolen_reserved(struct
> drm_i915_private *dev_priv,
>  		return;
>  	}
>  
> +	/*
> +	 * Whether ILK really reuses the ELK register for this is
> unclear.
> +	 * Let's see if we catch anyone with this supposedly enabled
> on ILK.
> +	 */
> +	WARN(IS_GEN5(dev_priv), "ILK stolen reserved found?
> 0x%08x\n", reg_val);

Since we're going to introduce an unconditional WARN, we may as well
print the value of GEN6_STOLEN_RESERVED, just in case?

Also, this will probably scare a lot of users. Maybe minimizing it to
DRM_ERROR would help. We could also consider expanding the message a
little bit more and explain that it's there for debugging purposes and
should be reported back to us?

I'll let the Maintainers make the decision on whether it's fine to add
a WARN like that. Please ping them.

Anyway, just like you, I don't have the documents to back up the claims
of the patch, so giving a R-B tag is quite hard.

Acked-by: Paulo Zanoni <paulo.r.zanoni@intel.com>




> +
>  	*base = (reg_val & G4X_STOLEN_RESERVED_ADDR2_MASK) << 16;
>  
>  	WARN_ON((reg_val & G4X_STOLEN_RESERVED_ADDR1_MASK) < *base);
> @@ -466,14 +472,12 @@ int i915_gem_init_stolen(struct
> drm_i915_private *dev_priv)
>  	case 3:
>  		break;
>  	case 4:
> -		if (IS_G4X(dev_priv))
> -			g4x_get_stolen_reserved(dev_priv,
> -						&reserved_base,
> &reserved_size);
> -		break;
> +		if (!IS_G4X(dev_priv))
> +			break;
> +		/* fall through */
>  	case 5:
> -		/* Assume the gen6 maximum for the older platforms.
> */
> -		reserved_size = 1024 * 1024;
> -		reserved_base = stolen_top - reserved_size;
> +		g4x_get_stolen_reserved(dev_priv,
> +					&reserved_base,
> &reserved_size);
>  		break;
>  	case 6:
>  		gen6_get_stolen_reserved(dev_priv,
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