[U-Boot] [linux-sunxi] Re: [PATCH] video: add cfb console driver for sunxi

[Maxime Ripard <maxime.ripard@free-electrons.com>]

On Tue, Aug 05, 2014 at 01:56:36PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 08/02/2014 06:14 PM, Luc Verhaegen wrote:
> > This adds a fixed mode hdmi driver (lcd to be added in future) for the
> > sunxi platform. Current config is such that 8MB is shaved off at the top
> > of the RAM. Simplefb support is available for kernels that know how to
> > use it.
> 
> I've been trying to follow all the discussion in this thread, and here
> is what I think we should do:
> 
> 1) There has been some discussion about using this console-driver
> in u-boot without generating the simplefb dt node. This means yet another
> variation in how all the bits fit together, so I don't think we should do
> this. Note I realize that the original patch did not have a specific
> config option for this, but it was mentioned later in the thread.
> TL;DR: Enabling the console driver will always generate the simplefb dt
> node.

Until we have a KMS driver, I agree.

The DT generation part should probably be a separate patch
though. It's probably going to generate enough discussion by itself to
not slow done the driver itself.

> 2) I think we can worry about what to do with the reserved memory\when not using simplefb
> (or when switching from simplefb to kms) later. For now lets focus on the
> issue with the clocks.
> 
> 3) To me the issue with clocks seems simple, we should modify the
> devicetree binding for simplefb to support a clocks property, and modify
> the simplefb kernel code to get + prep_and_enable any clocks specified
> in the dt node.
> 
> This means parsing enough of the dt to find the clocks to be able to
> specify phandles to them in the added node. I don't know how hard it will
> be to do this in u-boot, but IMHO it is simply the right thing to do, so
> this is how it should be done.
> 
> If others agree that specifying the clocks in the simplefb dt node is
> the right way to ensure that the clocks don't get enabled I'm willing
> at taking a shot on coding this.

Agreed.

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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