linux-kernel - Re: [PATCH 0/6] staging: BCM2835 MMAL V4L2 camera driver

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Date:   Sun, 19 Mar 2017 10:04:28 -0700
From:   Michael Zoran <mzoran@...wfest.net>
To:     Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Eric Anholt <eric@...olt.net>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 0/6] staging: BCM2835 MMAL V4L2 camera driver

On Sun, 2017-03-19 at 13:58 -0300, Mauro Carvalho Chehab wrote:
> Em Fri, 17 Mar 2017 17:34:36 -0700
> Eric Anholt <eric@...olt.net> escreveu:
> 
> > Mauro Carvalho Chehab <mchehab@...pensource.com> writes:
> > 
> > > Em Wed, 15 Mar 2017 18:46:24 -0700
> > > Michael Zoran <mzoran@...wfest.net> escreveu:
> > > 
> > > > On Wed, 2017-03-15 at 22:08 -0300, Mauro Carvalho Chehab wrote:
> > > > 
> > > > > No, I didn't. Thanks! Applied it but, unfortunately, didn't
> > > > > work.
> > > > > Perhaps I'm missing some other patch. I'm compiling it from
> > > > > the Greg's staging tree (branch staging-next):
> > > > > 	https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/
> > > > > staging.
> > > > > git/log/?h=staging-next
> > > > > 
> > > > > Btw, as I'm running Raspbian, and didn't want to use compat32
> > > > > bits, 
> > > > > I'm compiling the Kernel as an arm32 bits Kernel.
> > > > > 
> > > > > I did a small trick to build the DTB on arm32:
> > > > > 
> > > > > 	ln -sf ../../../arm64/boot/dts/broadcom/bcm2837-rpi-3-
> > > > > b.dts
> > > > > arch/arm/boot/dts/bcm2837-rpi-3-b.dts
> > > > > 	ln -sf ../../../arm64/boot/dts/broadcom/bcm2837.dtsi
> > > > > arch/arm/boot/dts/bcm2837.dtsi
> > > > > 	git checkout arch/arm/boot/dts/Makefile
> > > > > 	sed "s,bcm2835-rpi-zero.dtb,bcm2835-rpi-zero.dtb
> > > > > bcm2837-rpi-3-
> > > > > b.dtb," a && mv a arch/arm/boot/dts/Makefile
> > > > >   
> > > > 
> > > > Two other hacks are currently needed to get the camera to work:
> > > > 
> > > > 1. Add this to config.txt(This required to get the firmware to
> > > > detect
> > > > the camera)
> > > > 
> > > > start_x=1
> > > > gpu_mem=128
> > > 
> > > I had this already.
> > > 
> > > > 
> > > > 2. VC4 is incompatible with the firmware at this time, so you
> > > > need 
> > > > to presently munge the build configuration. What you do is
> > > > leave
> > > > simplefb in the build config(I'm assuming you already have
> > > > that), but
> > > > you will need to remove VC4 from the config.
> > > > 
> > > > The firmware currently adds a node for a simplefb for debugging
> > > > purposes to show the boot log.  Surprisingly, this is still
> > > > good enough
> > > > for basic usage and testing.  
> > > 
> > > That solved the issue. Thanks! It would be good to add a notice
> > > about that at the TODO, not let it build if DRM_VC4.
> > > 
> > > Please consider applying the enclosed path.
> > 
> > The VC4 incompatibility (camera firmware's AWB ends up briefly
> > using the
> > GPU, without coordinating with the Linux driver) is supposed to be
> > fixed
> > in current firmware
> > (https://github.com/raspberrypi/firmware/issues/760#issuecomment-28
> > 7391025)
> 
> With the current firmware, when X starts, the screen becomes blank,
> with upstream Kernel (it works with the downstream Kernel shipped
> with 
> the firmware).
> 
> Maybe something changed at DT?
> 
> Thanks,
> Mauro

Hi, exactly which DT are you using and which drivers are you using for
video. If this is a RPI 3, then as you know VC4 doesn't work due to the
HDMI hotplug issue. So I'm not 100% sure how you were getting video.

A working DT that I tried this morning with the current firmware is
posted here:
http://lists.infradead.org/pipermail/linux-rpi-kernel/2017-March/005924
.html

It even works with minecraft_pi!