Date:	Fri, 28 Mar 2014 13:27:30 -0500
From:	delicious quinoa <delicious.quinoa@...il.com>
To:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <robherring2@...il.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Matt Porter <matt.porter@...aro.org>,
	Koen Kooi <koen@...inion.thruhere.net>,
	Alison Chaiken <Alison_Chaiken@...tor.com>,
	Dinh Nguyen <dinh.linux@...il.com>,
	Jan Lubbe <jluebbe@...net.de>,
	Alexander Sverdlin <alexander.sverdlin@....com>,
	Michael Stickel <ms@...able.de>,
	Guenter Roeck <linux@...ck-us.net>,
	Dirk Behme <dirk.behme@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Michael Bohan <mbohan@...eaurora.org>,
	Ionut Nicu <ioan.nicu.ext@....com>,
	Michal Simek <monstr@...str.eu>,
	Matt Ranostay <mranostay@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Pete Popov <pete.popov@...sulko.com>,
	Dan Malek <dan.malek@...sulko.com>,
	Georgi Vlaev <georgi.vlaev@...sulko.com>
Subject: Re: [PATCH v3 0/7] Introducing (yet again) Device Tree Overlays

On Tue, Mar 18, 2014 at 4:55 PM, Pantelis Antoniou
<pantelis.antoniou@...sulko.com> wrote:
> The following patchset introduces Device Tree overlays, a method
> of dynamically altering the kernel's live Device Tree, along with
> a generic interface to use it in a board agnostic manner.
>
> It is dependent on Grant Likely's DT kobjectification patches located
> in his tree as queued for -next.
>
> It relies on the following previously submitted patches/patchsets:
>
> * OF: Add [__]of_find_node_by_full_name
> * OF: Utility helper functions for dynamic nodes
> * of: Make of_find_node_by_path() handle /aliases
>
> To compile overlays you need the DTC compiler patch
>
> * "dtc: Dynamic symbols & fixup support (v2)"
>
> Changes since V2:
> * Use of a configfs board agnostic overlay method
> * Use of per bus handlers instead of hardcoded behaviour
> * Optional target-path overlay target, which allows one to use standard
> DTBs without resolution options.
>
> Changes since V1:
>
> * Removal of any bits related to a specific board (beaglebone).
> * Introduced a platform agnostic interface using /proc/device-tree-overlay
> * Various bug fixes related to i2c device handling have been squashed in.
>
>
> Pantelis Antoniou (7):
>   OF: Introduce Device Tree resolve support.
>   OF: Introduce DT overlay support.
>   OF: DT-Overlay configfs interface
>   OF: platform: Add overlay bus handler
>   OF: i2c: Add overlay bus handler
>   OF: spi: Add overlay bus handler
>   of: i2c: Export single device registration method
>
>  .../devicetree/dynamic-resolution-notes.txt        |  25 +
>  Documentation/devicetree/overlay-notes.txt         | 187 +++++
>  drivers/base/platform.c                            |  99 ++-
>  drivers/i2c/i2c-core.c                             | 186 +++--
>  drivers/of/Kconfig                                 |  24 +
>  drivers/of/Makefile                                |   3 +
>  drivers/of/configfs.c                              | 272 +++++++
>  drivers/of/overlay.c                               | 895 +++++++++++++++++++++
>  drivers/of/resolver.c                              | 376 +++++++++
>  drivers/spi/spi.c                                  | 345 +++++---
>  include/linux/i2c.h                                |  10 +
>  include/linux/of.h                                 | 170 ++++
>  12 files changed, 2440 insertions(+), 152 deletions(-)
>  create mode 100644 Documentation/devicetree/dynamic-resolution-notes.txt
>  create mode 100644 Documentation/devicetree/overlay-notes.txt
>  create mode 100644 drivers/of/configfs.c
>  create mode 100644 drivers/of/overlay.c
>  create mode 100644 drivers/of/resolver.c

I can get a NULL pointer when I apply and remove an overlay and the
conditions are right.  The overlay applies correctly.  The crash is
when I do the rmdir.  My overlay is:

/dts-v1/;
/plugin/;
/ {
    fragment@0 {
        target-path="/soc";
        __overlay__ {
            #address-cells = <1>;
                    #size-cells = <1>;
            agpio0: agpio0 {
                compatible = "altr,pio-1.0";
                reg = <0xff210040 0x10>;
                interrupts = <0 45 4>;
                altr,gpio-bank-width = <32>;
                altr,interrupt_type = <1>;
                #gpio-cells = <2>;
                gpio-controller;
                #interrupt-cells = <1>;
                interrupt-controller;
            };
        };
    };
};

The log info I have is:

root@...fpga_cyclone5:~# ./do-overlay-only
+ mkdir /config/device-tree/overlays/foo
+ echo socfpga_overlay.dtbo
+ rmdir /config/device-tree/overlays/foo
Unable to handle kernel NULL pointer dereference at virtual address 00000018
pgd = bf164000
[00000018] *pgd=3fb9c831, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] SMP ARM
Modules linked in:
CPU: 1 PID: 175 Comm: rmdir Not tainted 3.13.0-00299-g2e61581 #7
task: bf00f400 ti: bfba4000 task.ti: bfba4000
PC is at release_resource+0x24/0x98
LR is at release_resource+0x20/0x98
pc : [<800286e0>]    lr : [<800286dc>]    psr: 60000013
sp : bfba5da0  ip : bfba5da0  fp : bfba5db4
r10: 00100100  r9 : 00000000  r8 : 00200200
r7 : 80732ff8  r6 : 00000001  r5 : bfbb8400  r4 : bfbd1100
r3 : 00000000  r2 : 00000000  r1 : 00000002  r0 : 8074e580
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 10c5387d  Table: 3f16404a  DAC: 00000015
Process rmdir (pid: 175, stack limit = 0xbfba4248)
Stack: (0xbfba5da0 to 0xbfba6000)
5da0: 00000000 00000001 bfba5dcc bfba5db8 802f2e40 800286c8 bfbb8400 bfb930c0
5dc0: bfba5de4 bfba5dd0 802f31e0 802f2dd0 bfbb8434 bfbb8400 bfba5dfc bfba5de8
5de0: 802f3224 802f31d0 802f31ec 807410ac bfba5e24 bfba5e00 803b4f20 802f31f8
5e00: bfb930c0 bfbe61a8 bfbe61a8 bfbe6180 00200200 00100100 bfba5e4c bfba5e28
5e20: 803b4fec 803b4e68 bfbe6140 ffffffff bfbe6188 00000000 80782dd4 80741108
5e40: bfba5e6c bfba5e50 803b51ec 803b4f94 00001040 bf82e000 807410b4 00000000
5e60: bfba5e84 bfba5e70 803b57f0 803b51b4 803b5778 bf82e018 bfba5ea4 bfba5e88
5e80: 80161df8 803b5784 00000000 00000000 bf82e000 bfb26070 bfba5eb4 bfba5ea8
5ea0: 80161e64 80161d9c bfba5eec bfba5eb8 8016071c 80161e28 80110da0 8010efbc
5ec0: bf59a198 bf59a198 00000000 bf5543f0 7e96ef14 ffffff9c bfba4000 bf59a198
5ee0: bfba5f0c bfba5ef0 801086e4 8016054c bf5533b8 bf128000 00000000 00000000
5f00: bfba5f94 bfba5f10 80108870 80108650 bf8e3010 bf5533b8 006f6f66 00000003
5f20: bf12802d 80107348 00000000 bf576660 bf5543f0 00000000 00000004 00000060
5f40: 00000000 00000000 bfba5f64 bfba5f58 800fcb1c 8003f114 bfba5f84 bfba5f68
5f60: 8003f114 804d1630 bfba4000 bfba4000 7e96ef14 00000000 7e96ee28 00000028
5f80: 8000ece4 00000000 bfba5fa4 bfba5f98 8010a800 8010875c 00000000 bfba5fa8
5fa0: 8000eac0 8010a7ec 7e96ef14 00000000 7e96ef14 00000000 00000002 7e96ee28
5fc0: 7e96ef14 00000000 7e96ee28 00000028 00000002 7e96ee24 0006a754 00000000
5fe0: 76f3d450 7e96ec74 0003c2e5 76f3d45c 80000010 7e96ef14 00000000 00000000
[<800286e0>] (release_resource+0x24/0x98) from [<802f2e40>]
(platform_device_del+0x7c/0xac)
[<802f2e40>] (platform_device_del+0x7c/0xac) from [<802f31e0>]
(platform_device_unregister+0x1c/0x28)
[<802f31e0>] (platform_device_unregister+0x1c/0x28) from [<802f3224>]
(platform_handler_remove+0x38/0x54)
[<802f3224>] (platform_handler_remove+0x38/0x54) from [<803b4f20>]
(of_overlay_device_entry_change.isra.0+0xc4/0x12c)
[<803b4f20>] (of_overlay_device_entry_change.isra.0+0xc4/0x12c) from
[<803b4fec>] (of_overlay_revert_one+0x64/0x220)
[<803b4fec>] (of_overlay_revert_one+0x64/0x220) from [<803b51ec>]
(of_overlay_revert+0x44/0x64)
[<803b51ec>] (of_overlay_revert+0x44/0x64) from [<803b57f0>]
(cfs_overlay_release+0x78/0x7c)
[<803b57f0>] (cfs_overlay_release+0x78/0x7c) from [<80161df8>]
(config_item_release+0x68/0x8c)
[<80161df8>] (config_item_release+0x68/0x8c) from [<80161e64>]
(config_item_put+0x48/0x4c)
[<80161e64>] (config_item_put+0x48/0x4c) from [<8016071c>]
(configfs_rmdir+0x1dc/0x264)
[<8016071c>] (configfs_rmdir+0x1dc/0x264) from [<801086e4>]
(vfs_rmdir+0xa0/0x10c)
[<801086e4>] (vfs_rmdir+0xa0/0x10c) from [<80108870>] (do_rmdir+0x120/0x150)
[<80108870>] (do_rmdir+0x120/0x150) from [<8010a800>] (SyS_rmdir+0x20/0x24)
[<8010a800>] (SyS_rmdir+0x20/0x24) from [<8000eac0>] (ret_fast_syscall+0x0/0x30)
Code: e1a04000 e59f0074 eb12b02b e5943010 (e5932018)
---[ end trace 1b8539e83d8e0ecc ]---
./do-overlay-only: line 7:   175 Segmentation fault      rmdir
/config/device-tree/overlays/foo
root@...fpga_cyclone5:~#

I did some debug, haven't figured anything out yet.

I have been able to successfully add/remove an overlay if it was to a
fpga node that was at /fpga and used 'target = <&fpga>;'   Also
'target-path="/fpga";' works fine.

Alan Tull
aka
delicious quinoa
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