[PATCH/RESEND 9/9] drm/tilcdc: replace late_initcall with module_init

[ezequiel@vanguardiasur.com.ar (Ezequiel García)]

(Ccing Guido back)

Hello Russell, Darren,

On 25 Jun 02:00 PM, Russell King - ARM Linux wrote:
> On Tue, Jun 24, 2014 at 05:04:36PM -0500, Darren Etheridge wrote:
> > On 06/17/2014 09:17 AM, Guido Mart?nez wrote:
> >> Use module_init instead of late_initcall, as is the norm for modular
> >> drivers.
> >>
> >> module_init was used until 6e8de0bd6a51fdeebd5d975c4fcc426f730b339b
> >> ("drm/tilcdc: add encoder slave (v2)") changed it to a late_initcall,
> >> but it does not explain why. Tests show it's working properly with
> >> module_init.
> >>
> >
> > If I recall, the late_initcall stuff was done to try and make sure the  
> > tda998x/i2c subsystem came up before tilcdc.

That doesn't make any sense. Using late_initcall for the tilcdc DRM
driver would make the tilcdc DRM get probed before any other regular
module_init driver, including the tda998x encoder.

> > However it didn't always  
> > work so we added commit: 39de6194131c155901f96686a063212656d80c2e to try  
> > and ensure the ordering.  This might be why changing back to module_init  
> > is fine (and I agree with your assessment from my testing).

That commit is adds a proper probe deferal mechanism in case the
i2c is not available. OMAP is special because it has its own nasty initcall
to probe the i2c busses. However, that should be fixed and then i2c would be
always probed *after* the DRM, as per the ordering in drivers/Makefile.

> 
> There's a solution to that...

A solution to *what* ?

> I have patches which convert the tda998x
> driver to also register into the component helpers as well as remaining
> as a drm slave device.  This makes it possible to transition tilcdc to
> use the component helper to solve the initialisation ordering.
> 

AFAIK, there's no issue with the initialisation ordering, except that the
DRM driver is currently probed before the TDA998x encoder and so the probe
is defered. Unless I'm missing something that's very easy to fix, you just
need to change the link order to guarantee that i2c encoders are probed
*before* the DRM drivers that require them.

I have just posted a very simple patch to fix it, but it seems Thierry wasn't
happy with it, not sure why yet [1].

[1] http://www.spinics.net/lists/dri-devel/msg61987.html
-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar