linux-kernel - Re: 4.13 (and probably all recent) kernels refuse to boot on one Nokia N950, work or another

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Message-ID: <20171026093115.4bc6ctxjx72ng7ld@earth>
Date:   Thu, 26 Oct 2017 11:31:15 +0200
From:   Sebastian Reichel <sre@...nel.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Tony Lindgren <tony@...mide.com>, pali.rohar@...il.com,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        clayton@...ftyguy.net, martijn@...xit.nl,
        sakari.ailus@...ux.intel.com, filip.matijevic.pz@...il.com
Subject: Re: 4.13 (and probably all recent) kernels refuse to boot on one
 Nokia N950, work or another

Hi,

On Thu, Oct 26, 2017 at 11:13:26AM +0200, Pavel Machek wrote:
> On Wed 2017-10-25 14:28:07, Tony Lindgren wrote:
> > * Pavel Machek <pavel@....cz> [171025 13:36]:
> > > Hi!
> > > 
> > > ...hardware should be identical. 3.5.3-nemo kernel seems to work on
> > > both. 4.13-rc2 with display and clock patches boots on phone "S", but
> > > does not on phone "P"; nothing nothing is received on serial port.
> > > 
> > > There is some difference in the bootloaders: S's bootloader provides
> > > lots of debug info, P's is silent. R&D settings do _not_ have
> > > influence on bootloader. We know P's serial works, as 3.5.3 kernel
> > > prints "Uncompressing linux...booting" there.
> > > 
> > > I'll need to return "S" phone and serial cable tommorow. If you have
> > > any ideas, let me know.
> > 
> > If you get nothing out of the uart, chances are the pins are
> > not muxed for the uart in nolo and maybe kernel dts is missing the
> > pinctrl entries for uart?
> > 
> > Also try booting with mem=512M@...0000000 or 256M or 768M. Maybe the
> > memory is different size or partially broken?
> 
> Uhuh. It looks like "P" nokia really wants initrd, otherwise it will
> not boot.
> 
> I got "uncompressing Linux 4.13" on serial console now, debug LEDs
> blinking, and if I use a flashlight, I see output on the screen, too.
> 
> (What do I need to do to get the backlight working?)

Glad you got it working :) For backlight you can add this
in drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c:

add the following code at the end of dsicm_probe:

-----------------------------------------------------------
mutex_unlock(&ddata->lock);
mutex_lock(&ddata->lock);
ddata->in->ops.dsi->bus_lock(ddata->in);
r = dsicm_wake_up(ddata);
if (!r)
    r = dsicm_dcs_write_1(ddata, DCS_BRIGHTNESS, 100);
ddata->in->ops.dsi->bus_unlock(ddata->in);
mutex_unlock(&ddata->lock);
-----------------------------------------------------------

-- Sebastian

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