[Intel-gfx] [PATCH 02/20] drm/i915: Set PCH as NOP when display is disabled

[Jani Nikula]

On Wed, 08 Aug 2018, José Roberto de Souza <jose.souza at intel.com> wrote:
> num_pipes is set to 0 if disable_display is set inside
> intel_device_info_runtime_init() but when that happen PCH will
> already be set in intel_detect_pch().
>
> i915_driver_load()
> 	i915_driver_init_early()
> 		...
> 		intel_detect_pch()
> 		...
> 	...
> 	i915_driver_init_hw()
> 		intel_device_info_runtime_init()
>
> So now setting num_pipes = 0 earlier to avoid this problem.

Okay, this gets confusing. There are other paths in
intel_device_info_runtime_init() that set num_pipes = 0 and depend on
PCH having been detected. :(

>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.c          | 5 +++++
>  drivers/gpu/drm/i915/intel_device_info.c | 8 ++------
>  2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 9dce55182c3a..7952f5877402 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -917,6 +917,11 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv,
>  	if (ret < 0)
>  		goto err_workqueues;
>  
> +	if (i915_modparams.disable_display) {
> +		DRM_INFO("Display disabled (module parameter)\n");
> +		device_info->num_pipes = 0;
> +	}
> +

Please look at the function as a whole, and note that this feels like a
random thing to add in the middle. Needs to be stowed away somewhere
deeper.

Overall, I think we need to be more accurate about the relationship of
num_pipes = 0 and PCH_NOP.


BR,
Jani.

>  	/* This must be called before any calls to HAS_PCH_* */
>  	intel_detect_pch(dev_priv);
>  
> diff --git a/drivers/gpu/drm/i915/intel_device_info.c b/drivers/gpu/drm/i915/intel_device_info.c
> index 0ef0c6448d53..67102b481c8f 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.c
> +++ b/drivers/gpu/drm/i915/intel_device_info.c
> @@ -776,12 +776,8 @@ void intel_device_info_runtime_init(struct intel_device_info *info)
>  			info->num_sprites[pipe] = 1;
>  	}
>  
> -	if (i915_modparams.disable_display) {
> -		DRM_INFO("Display disabled (module parameter)\n");
> -		info->num_pipes = 0;
> -	} else if (info->num_pipes > 0 &&
> -		   (IS_GEN7(dev_priv) || IS_GEN8(dev_priv)) &&
> -		   HAS_PCH_SPLIT(dev_priv)) {
> +	if (info->num_pipes > 0 && (IS_GEN7(dev_priv) || IS_GEN8(dev_priv)) &&
> +	    HAS_PCH_SPLIT(dev_priv)) {
>  		u32 fuse_strap = I915_READ(FUSE_STRAP);
>  		u32 sfuse_strap = I915_READ(SFUSE_STRAP);

-- 
Jani Nikula, Intel Open Source Graphics Center