Re: [PATCH] drm/exynos: Make exynos_drm_init() call late during the bootup

[Thierry Reding <thierry.reding@gmail.com>]

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On Wed, May 14, 2014 at 05:09:45PM +0530, Naveen Krishna Chatradhi wrote:
> exynos_drm_init() does probing of various drivers like dp_panel,
> hdmi, fimd, mixer, etc in an order and finally binds them together.
> 
> Some of the drm devices (Eg: dp_panel) try to do regulator_get()
> and enable few supplies during their probe.
> Chances are that, these devices may get probed before the respective
> supply/PMIC is hooked.  In such cases, dp_panel would continue with
> "dummy regulator". Which is not what the system wants.
> 
> Lets give the core connectivity and regulators modules some time
> to hookup the supplies before Exynos DRM devices comes into picture.
> 
> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
> ---
> This change is proposed after
> 1. Discussing with I2C/SPI & DMA subsystem maintainers and Others
>    @ https://lkml.org/lkml/2014/5/9/333
>    Trying to change the I2C, SPI and DMA drivers as subsys_initcall()
>    Which was strictly opposed, as a flaw was found in DRM subsystem.
> 
> 2. -EPROBE_DEFER won't work well with the current sequency of
>     platform_driver_register()s in exynos_drm_init()

Then this is the problem that you need to fix. If the driver doesn't
handle -EPROBE_DEFER properly then that means the driver is broken. No
amount of initcall ordering can fix this for you.

Thierry

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