Re: [RFC PATCH 0/6] Boot logo supplied by the device tree

[Maxime Ripard <mripard@kernel.org>]

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Hi,

On Sun, Aug 02, 2026 at 12:01:58AM +0200, Màxim Pedraza Padilla wrote:
> Uwe Kleine-König wrote:
> > My 0.02€: Usually you want to use the display using drm and not fb once
> > the machine is fully booted. If you're using fb during boot to display a
> > logo, it's hardly possible to switch to drm later in the boot process
> > without flicker.
> >
> > So my recommendation for your usecase is to not use the kernel boot logo
> > stuff, but something like https://github.com/pengutronix/platsch.
> 
> Thanks for the pointer, I did not know platsch and it looks like a good
> fit for the problem it solves. It does not solve mine, though, and I
> think the reason is worth spelling out, because it is not about how the
> image gets drawn but about when.
> 
> These are industrial units, and the requirement is time to first pixel
> after power is applied. If the panel stays dark for more than a moment
> the unit reads as dead, and that is a support call. Anything running in
> userspace is by construction later than the kernel: it needs the kernel
> booted, the rootfs mounted and init far enough along to exec it. I can
> measure the exact difference on our hardware if that is useful for the
> discussion.
> 
> We do already paint a BMP from U-Boot, which is as early as we can
> possibly be. The problem is the gap that follows: once the display
> driver probes, the panel is cleared, and nothing puts anything back
> until userspace is running. Moving the logo further out into userspace
> widens that gap rather than closing it. The kernel boot logo is what
> fills it, and that is the whole reason this series exists.

If the sole reason for this series is to keep having something on the
display while the kernel boots until DRM catches up, then you probably
want to check

https://lore.kernel.org/r/20260629-drm-state-readout-v4-0-5966657980ed@kernel.org

Which also does what you're trying to achieve: keep the display running
with the same content while the DRM driver loads, and switch to whatever
comes next without a flicker (if we can).

Maxime

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