Seemless Boot Splash on iMX-based boards

Seemless Boot Splash on iMX-based boards

[Igor Opaniuk]

Hi,

Does anyone have experience in setting up seamless
boot splash on iMX-based platforms?

I'm currently trying to do that on iMX7-based board with
4.9 2.3.x IMX downstream kernel running.

I've backported console deferred takeover patch-series for fbcon [1],
which permits the contents of the framebuffer (initialized before in U-Boot)
to stay in place as is till error message is shown
or boot is finished.

The initial splash is shown in U-Boot(mainline) (mxsfb driver is used
for controller/fb initialization).

Nevertheless, MXSFB controller every time keeps resetting just after
U-Boot->Linux takeover and fb is cleared (I see a black screen) till
login request shows up.

Questions:
1. Did anyone have a chance to work on such setups based on deferred
console "feature"?
2. Does it make sense at all to continue moving towards with this approach
(we initialize graphics core and show boot splash by firmware/bootloader,
then hand over it to Linux).
Taking into account on-going transition to DRM/KMS in the mainline kernel
and that fact that there is no any mainline compatible way to take over
an initialized graphics core, I assume the only generic solution could be
avoiding showing boot logo at all and do that only from the Linux (
Plymouth-based etc.)

Any comments are welcome. Thanks!

[1] https://patchwork.kernel.org/patch/10432641/

-- 
Best regards - Freundliche Gr?sse - Meilleures salutations

Igor Opaniuk

mailto: igor.opaniuk at gmail.com
skype: igor.opanyuk
+380 (93) 836 40 67
http://ua.linkedin.com/in/iopaniuk

Seemless Boot Splash on iMX-based boards

[Stefano Babic]

Hi Igor,

my two cents from previous experience:

On 06.07.20 10:34, Igor Opaniuk wrote:
> Hi,
> 
> Does anyone have experience in setting up seamless
> boot splash on iMX-based platforms?
> 
> I'm currently trying to do that on iMX7-based board with
> 4.9 2.3.x IMX downstream kernel running.
> 

Well, i.MX7 have a chance because it has no GPU. I did this for TI based
boards, too.

But let me say that it is tricky and it creates big dependencies between
U-Boot and kernel. And to get a flicker-free images, the clock setup
should be exactly the same between U-Boot and kernel, and this is not
often (or never) the same because we need a lot of more features
(layers, overlays, ..) in kernel, while we just to need to show
something like a logo in U-Boot.

With the introduction of DRM, things are more difficult. Take also into
account that a small change in kernel can be enough to have a weird
transition on the framebuffer, and it is more nasty as to start with a
black screen.

> I've backported console deferred takeover patch-series for fbcon [1],
> which permits the contents of the framebuffer (initialized before in U-Boot)
> to stay in place as is till error message is shown
> or boot is finished.
> 
> The initial splash is shown in U-Boot(mainline) (mxsfb driver is used
> for controller/fb initialization).
> 
> Nevertheless, MXSFB controller every time keeps resetting just after
> U-Boot->Linux takeover and fb is cleared (I see a black screen) till
> login request shows up.

Right.

> 
> Questions:
> 1. Did anyone have a chance to work on such setups based on deferred
> console "feature"?
> 2. Does it make sense at all to continue moving towards with this approach
> (we initialize graphics core and show boot splash by firmware/bootloader,
> then hand over it to Linux).

My personal point of view: it makes much more sense to invest the time
to speed up the boot process, and let the kernel to boot in a shorten
time. And if this time is short enough, kernel has initialized the
framebuffer and can show something. This leads also to the main focus
for U-Boot, that should be to start the kernel in the shortest time
possible.

> Taking into account on-going transition to DRM/KMS in the mainline kernel

Fully agree.

> and that fact that there is no any mainline compatible way to take over
> an initialized graphics core, I assume the only generic solution could be
> avoiding showing boot logo

This is my position, too, and I do not show logo in U-Boot since some
years (ok, since starting from DRM /KMS). And well, with i.MX6 / i.MX8,
I do not see a chance without a very big effort, and IMHO it is not
worth of it.

> at all and do that only from the Linux (
> Plymouth-based etc.)

Agree.

> 
> Any comments are welcome. Thanks!
> 
> [1] https://patchwork.kernel.org/patch/10432641/
> 

Best regards,
Stefano

-- 
=====================================================================
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
=====================================================================

Seemless Boot Splash on iMX-based boards

[Igor Opaniuk]

Hi Stefano,

On Mon, Jul 6, 2020 at 12:10 PM Stefano Babic <sbabic@denx.de> wrote:
>
> Hi Igor,
>
> my two cents from previous experience:
>
> On 06.07.20 10:34, Igor Opaniuk wrote:
> > Hi,
> >
> > Does anyone have experience in setting up seamless
> > boot splash on iMX-based platforms?
> >
> > I'm currently trying to do that on iMX7-based board with
> > 4.9 2.3.x IMX downstream kernel running.
> >
>
> Well, i.MX7 have a chance because it has no GPU. I did this for TI based
> boards, too.
>
> But let me say that it is tricky and it creates big dependencies between
> U-Boot and kernel. And to get a flicker-free images, the clock setup
> should be exactly the same between U-Boot and kernel, and this is not
> often (or never) the same because we need a lot of more features
> (layers, overlays, ..) in kernel, while we just to need to show
> something like a logo in U-Boot.
>
> With the introduction of DRM, things are more difficult. Take also into
> account that a small change in kernel can be enough to have a weird
> transition on the framebuffer, and it is more nasty as to start with a
> black screen.
>
> > I've backported console deferred takeover patch-series for fbcon [1],
> > which permits the contents of the framebuffer (initialized before in U-Boot)
> > to stay in place as is till error message is shown
> > or boot is finished.
> >
> > The initial splash is shown in U-Boot(mainline) (mxsfb driver is used
> > for controller/fb initialization).
> >
> > Nevertheless, MXSFB controller every time keeps resetting just after
> > U-Boot->Linux takeover and fb is cleared (I see a black screen) till
> > login request shows up.
>
> Right.
>
> >
> > Questions:
> > 1. Did anyone have a chance to work on such setups based on deferred
> > console "feature"?
> > 2. Does it make sense at all to continue moving towards with this approach
> > (we initialize graphics core and show boot splash by firmware/bootloader,
> > then hand over it to Linux).
>
> My personal point of view: it makes much more sense to invest the time
> to speed up the boot process, and let the kernel to boot in a shorten
> time. And if this time is short enough, kernel has initialized the
> framebuffer and can show something. This leads also to the main focus
> for U-Boot, that should be to start the kernel in the shortest time
> possible.
>
> > Taking into account on-going transition to DRM/KMS in the mainline kernel
>
> Fully agree.
>
> > and that fact that there is no any mainline compatible way to take over
> > an initialized graphics core, I assume the only generic solution could be
> > avoiding showing boot logo
>
> This is my position, too, and I do not show logo in U-Boot since some
> years (ok, since starting from DRM /KMS). And well, with i.MX6 / i.MX8,
> I do not see a chance without a very big effort, and IMHO it is not
> worth of it.
>
> > at all and do that only from the Linux (
> > Plymouth-based etc.)
>
> Agree.
>
> >
> > Any comments are welcome. Thanks!
> >
> > [1] https://patchwork.kernel.org/patch/10432641/
> >
>
> Best regards,
> Stefano
>
> --
> =====================================================================
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
> =====================================================================

Thanks a lot for your valuable input!

-- 
Best regards - Freundliche Gr?sse - Meilleures salutations

Igor Opaniuk

mailto: igor.opaniuk at gmail.com
skype: igor.opanyuk
+380 (93) 836 40 67
http://ua.linkedin.com/in/iopaniuk