[Intel-gfx] [PATCH 0/7] drm/i915: Move some load time init steps earlier

[Chris Wilson]

On Wed, Mar 09, 2016 at 05:31:39PM +0200, Imre Deak wrote:
> While working on the CDCLK init code I realized that the driver load time
> dependencies between the different init steps are rather difficult to follow
> and so it's not obvious where some new piece of initialization needs to be
> added.
> 
> Also because some things are initialized too late, other steps depending on
> these must be initialized in a non-logical place or even split into multiple
> parts. One example is the CDCLK initialization which needs the display
> callbacks to be set already, but those callbacks are setup only late, so the
> CDCLK initialization must be done in two parts.
> 
> As a generic solution, I suggest that we define the following load
> time init phases:
> - state init not requiring device access
>   (i.e SW only, like initializing locks, allocating system memory, setting
>    up callbacks, device attributes)
> - minimal HW setup to enable MMIO access to the device
> - state init requiring device access w/o side effects
>   (i.e. read-only HW access, no interface registrations)
> - state init causing device-wide side effects
>   (i.e any HW access, no interface registration)
> - registering all interfaces

On paper sounds goods. The only complaint I have is that we have only
nomenclature for 2 phases: init and init_hw. To be compelling I want
consistent names for each init function so that we know at a glance what
phase we are in, and the expectations/limitations upon the function.

init_early() / setup()
init_mmio()
init_late()
init_hw()

> This patchset adds the corresponding comment markers for the first
> two phases above and one common phase for the rest of the current
> init steps. Later we could also add the last three init phases above
> and restructure the code accordingly.
> 
> For now I only moved earlier a few obvious init steps that fit these
> new phases.
> 
> I smoke tested this on GEN4, SNB, BXT.
> 
> Imre Deak (7):
>   drm/i915: Add comments marking the start of load time init phases
>   drm/i915: Move laod time PCH detect, DPIO, power domain SW init
>     earlier
>   drm/i915: Move load time IRQ SW init earlier
>   drm/i915: Move load time display/audio callback init earlier
>   drm/i915: Move load time clock gating callback init earlier
>   drm/i915: Move load time runtime device info init earlier
>   drm/i915: Move load time runtime PM get later

Lgtm.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre