Hi everyone,
Background:
I was trying to get the mt9p031 sensor working on a BeagleBoard xM with
a patched 3.9.8 kernel[1] or with the Laurent Pinchart's omap3isp/xclk
branch[2]. I had this hardware working quite well under linux 3.2.8 and
3.2.24 with a patchset from Max Galemin but I had kernel crashes from
time to time so I wanted to give a more recent kernel a try.
Unfortunatelly I ran into some serious problems. I debugged them as far
as I could but I cannot even begin to think of fixing this on my own so
I would be really grateful if somebody could point me in the right
direction.
The problems:
1. I get a kernel deadlock when I run "media-ctl -p":
mt9p031_power_on calls clk_prepare_enable to get it's clock running
This, via isp_xclk_prepare -> omap3isp_get -> isp_enable_clocks results
in another call to clk_prepare_enable which causes a deadlock because of
the global prepare_lock in clk.c
2. Another thing is a lockdep warning during bootup:
It warns about mixing the ordering of prepare_lock & isp->isp_mutex. The
cause is that isp_probe acquires the isp_mutex first and then proceeds
to enable clocks (acquiring prepare_lock in the process). Later on when
the mt9p031 is intialized from v4l2_device_register_subdev it starts
with getting it's clock and later locks isp_mutex via omap3isp_get (the
deadlock does not happen in this case because the ISP clocks were
already enabled).
[1]: My patches agains vanilla 3.9.8 can be inspected here:
https://github.com/LoEE/buildroot/tree/daf8276e3629f9aa8540fdd3510859c811dd2d24/board/beagleboard/xm/kernel-patches
I have cherry-picked some omap3isp and mt9p031 patches from this mailing
list (and reinvented at least one of them myself). Other patches (most
of them) were taken from
https://github.com/RobertCNelson/stable-kernel/tree/v3.9.x
[2]: I made one change (to get cpu_is_omap3630 defined):
diff --git a/arch/arm/mach-omap2/board-omap3beagle-camera.c
b/arch/arm/mach-omap2/board-omap3beagle-camera.c
index bf84b48..cf5ad89e 100644
--- a/arch/arm/mach-omap2/board-omap3beagle-camera.c
+++ b/arch/arm/mach-omap2/board-omap3beagle-camera.c
@@ -18,6 +18,7 @@
#include <media/omap3isp.h>
#include "devices.h"
+#include "soc.h"
#define MT9P031_RESET_GPIO 98
--
regards,
Jakub Piotr Cłapa
LoEE.pl
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