[U-Boot] [PATCH] common: add board specific hook for os preboot config

[Michael Nazzareno Trimarchi]

Hi



On Thu., 16 Aug. 2018, 3:09 pm Stefan Agner, <stefan at agner.ch> wrote:

> On 13.08.2018 09:30, Gerard Salvatella wrote:
> > Some boards require specific configuration prior to booting the kernel.
> > For instance, our boards require shutting down the display to avoid
> > fading transitions before the drivers are reloaded by the kernel. This
> > could be facilitated by adding an extra hook during the os booting
> > process.
>
> Maybe I can extend on what we are trying to achieve here:
>
> We enable display backlight using board code.
>

You can make it works almost easily.

I enable simple fb, inject allocated display parameters in dts to reserve
area, pass the area to the graphics controller and dismiss it during probing

This is mainline in linux support.

I have couple of patches need to clean up for imx architecture (imx6ull and
imx25)

You can still scripting it using cmd interface

Michael

>
> The architecture code then shuts down the display controller just before
> booting Linux (e.g. on i.MX, by calling
> ipuv3_fb_shutdown/lcdif_power_down in arch_preboot_os).
>
> This leads to a display which has backlight enabled, but no data
> driven... Depending on display this leads to noisy/fading transitions
> between U-Boot and Linux.
>
> So we would like to disable the backlight in board code.
>
> In a first version we used a weak display_shutdown() function, but with
> that we would have to add it to every architecture.
>
> This approach uses a generic board specific preeboot_os callback which
> can be used for different purpose too.
>
> Does this sound like an approach which is acceptable upstream?
>
> --
> Stefan
>
>
> >
> > Signed-off-by: Gerard Salvatella <gerard.salvatella at toradex.com>
> > ---
> >  common/bootm_os.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/common/bootm_os.c b/common/bootm_os.c
> > index f4bd905909..1e7af56b64 100644
> > --- a/common/bootm_os.c
> > +++ b/common/bootm_os.c
> > @@ -505,9 +505,16 @@ __weak void arch_preboot_os(void)
> >         /* please define platform specific arch_preboot_os() */
> >  }
> >
> > +/* Allow for board specific config before we boot */
> > +__weak void board_preboot_os(void)
> > +{
> > +       /* please define board specific board_preboot_os() */
> > +}
> > +
> >  int boot_selected_os(int argc, char * const argv[], int state,
> >                      bootm_headers_t *images, boot_os_fn *boot_fn)
> >  {
> > +       board_preboot_os();
> >         arch_preboot_os();
> >         boot_fn(state, argc, argv, images);
> >
> > --
> > 2.18.0
> >
> >
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