Re: [PATCH v2 1/4] arm64: dts: rk3399-u-boot: Delete vop assigned-clocks/rates

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> From: Jagan Teki <jagan@amarulasolutions.com>
> Date: Thu, 2 Apr 2020 15:07:01 +0530
> 
> Hi Kever,
> 
> On Thu, Apr 2, 2020 at 2:48 PM Kever Yang <kever.yang@rock-chips.com> wrote:
> >
> > Hi Jagan,
> >
> > On 2020/3/31 下午1:59, Jagan Teki wrote:
> > > On Tue, Mar 31, 2020 at 1:06 AM Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> > >>> From: Jagan Teki <jagan@amarulasolutions.com>
> > >>> Cc: sunil@amarulasolutions.com, u-boot@lists.denx.de,
> > >>>          linux-rockchip@lists.infradead.org, linux-amarula@amarulasolutions.com,
> > >>>          Jagan Teki <jagan@amarulasolutions.com>
> > >>> Date: Mon, 30 Mar 2020 23:46:10 +0530
> > >>> Content-Type: text/plain; charset=UTF-8
> > >>>
> > >>> Linux supporting assigned-clocks for VOP on rk3399 by assuming
> > >>> U-Boot not initializing it on this linux commit:
> > >>>
> > >>> commit <617f4472bdd3> ("arm64: dts: rockchip: init rk3399 vop clock rates")
> > >>>
> > >>> There is no specific need to initialize these assigned clock
> > >>> in U-Boot as video drivers still work with default aclk and
> > >>> hclk values. So, these clocks are simply not supported by rk3399
> > >>> clock driver.
> > >>>
> > >>> But, during stdio probe of vidconsole, the device probe
> > >>> will try to check whether the assigned clocks on that video
> > >>> console node is initialized or not? and return error if not.
> > >>>
> > >>> So, delete these property via -u-boot dtsi as there is
> > >>> no specific need in U-Boot.
> > >> Deleting these properties isn't very helpful as it means the U-Boot
> > >> device tree can no longer be used by the kernel.  Isn't it a better
> > >> idea to implement these clocks as stubs in the u-boot clock driver?
> > > I did try this before sorting out these changes, seems like it
> > > requires a bit more tweaking the clock wrt display code. I really
> > > didn't see any use case as of now for just to print u-boot log on
> > > display out, and more over this support has been broken since from
> > > releases. so bypassing these nodes can be a solutions for now.
> >
> >
> > I agree with Mark for not touch the dts first. I don't know the detail
> > of display driver but:
> >
> > - The rk3399 driver use to work without touch dts from kernel;
> >
> > - the clock driver have a rk3399_vop_set_clk() which does not depends on
> > dts.
> 
> The existing video drivers are written based on the puma dts and those
> are not inline to Linux dts files, i.e. the reason the code is pushed
> I think. The rest of rk3399 dtsi files are now inline to Linux as and
> display out on these are broken from last 2 releases. so my idea is to
> resolve the things one-after-another like
> 1. Make existing video stuff work with all rk3399 (this series along
> with this patch)
> 2. Drop this patch change and make video drivers working w/o any
> explicit changes in dts like this patch does.
> 
> Since step 2, would take time, and require close testing of all boards
> I would like to pick the existing stuff for the release. Mark my words
> to fix the things for the next release.

Fair enough.  I don't think fixing the issue is too difficult, but it
is better to do these things in small steps anyway.