linux-kernel - Re: [PATCH v2 09/11] mfd: twl-core: Collect global variables behind one private structure (global)

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Date:	Wed, 13 Feb 2013 14:59:17 +0100
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Jon Hunter <jon-hunter@...com>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	Tero Kristo <t-kristo@...com>
Subject: Re: [PATCH v2 09/11] mfd: twl-core: Collect global variables behind
 one private structure (global)

Hi Jon,

On 02/12/2013 05:15 PM, Jon Hunter wrote:
> 
> On 02/12/2013 01:26 AM, Peter Ujfalusi wrote:
>> On 02/11/2013 09:22 PM, Jon Hunter wrote:
>>> Good point. I just noticed that none of my omap2+ board were booting and
>>> on omap3/4 I was the panic in the twl code. I can't say that I checked
>>> the panic on omap2, so may be that was another problem?
>>
>> Do you have insights on the code path leading to a crash on OMAP3/4? I have
>> been running this code on several boards (BeagleBoard, Zoom2, PandaBoard,
>> Blaze) and have not seen a crash.
> 
> Here is the panic log ...

Thanks.

> 
> [    2.286132] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [    2.294738] pgd = c0004000
> [    2.297576] [00000000] *pgd=00000000
> [    2.301361] Internal error: Oops: 5 [#1] SMP ARM
> [    2.306243] Modules linked in:
> [    2.309448] CPU: 0    Not tainted  (3.8.0-rc6-next-20130207-00016-g735c237 #35)
> [    2.317169] PC is at twl_i2c_read+0x3c/0xec
> [    2.321563] LR is at twl_i2c_read+0x1c/0xec
> [    2.325988] pc : [<c0333950>]    lr : [<c0333930>]    psr: 80000153
> [    2.325988] sp : c702fed0  ip : 00000000  fp : 00000000
> [    2.338043] r10: c702e000  r9 : c06e84e8  r8 : c06e51c8
> [    2.343536] r7 : 00000001  r6 : 00000006  r5 : c702fef6  r4 : 00000004
> [    2.350402] r3 : c129508c  r2 : 00000006  r1 : c702fef6  r0 : 0000000e
> [    2.357269] Flags: Nzcv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
> [    2.365051] Control: 10c5387d  Table: 80004019  DAC: 00000017
> [    2.371093] Process swapper/0 (pid: 1, stack limit = 0xc702e240)
> [    2.377410] Stack: (0xc702fed0 to 0xc7030000)
> [    2.382019] fec0:                                     c0d42180 c0d429d0 c70a7640 c07354c4
> [    2.390624] fee0: 00000001 c0719798 c0d42180 c06f2cc0 c04e76cc c06ee1ac 00000000 c07354c4
> [    2.399230] ff00: 00000007 c06f2d64 00000017 c06fb308 00000000 c06f07a4 c0cb8580 c06edee0
> [    2.407836] ff20: c06eded4 c06e8504 c0d42180 c0008768 0000009e c00611b4 00000001 00000000
> [    2.416442] ff40: c061994c c06b7548 00000007 00000007 00000000 c07354c4 00000007 c0719798
> [    2.425048] ff60: c0d42180 c06e51c8 c07197a0 0000009e 00000000 c06e590c 00000007 00000007
> [    2.433654] ff80: c06e51c8 00000000 00000000 c04d26ec 00000000 00000000 00000000 00000000
> [    2.442260] ffa0: 00000000 c04d26f4 00000000 c00137b0 00000000 00000000 00000000 00000000
> [    2.450866] ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    2.459472] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 80fb6c10 71bbcd20
> [    2.468078] [<c0333950>] (twl_i2c_read+0x3c/0xec) from [<c06f2cc0>] (omap3_twl_set_sr_bit+0x3c/0xb4)
> [    2.477722] [<c06f2cc0>] (omap3_twl_set_sr_bit+0x3c/0xb4) from [<c06f2d64>] (omap3_twl_init+0x2c/0x70)
> [    2.487518] [<c06f2d64>] (omap3_twl_init+0x2c/0x70) from [<c06fb308>] (omap_pmic_late_init+0x18/0x24)
> [    2.497222] [<c06fb308>] (omap_pmic_late_init+0x18/0x24) from [<c06f07a4>] (omap2_common_pm_late_init+0x18/0xd0)
> [    2.507934] [<c06f07a4>] (omap2_common_pm_late_init+0x18/0xd0) from [<c06edee0>] (omap3_init_late+0xc/0x18)
> [    2.518188] [<c06edee0>] (omap3_init_late+0xc/0x18) from [<c06e8504>] (init_machine_late+0x1c/0x28)
> [    2.527740] [<c06e8504>] (init_machine_late+0x1c/0x28) from [<c0008768>] (do_one_initcall+0x100/0x16c)
> [    2.537536] [<c0008768>] (do_one_initcall+0x100/0x16c) from [<c06e590c>] (kernel_init_freeable+0xfc/0x1c8)
> [    2.547698] [<c06e590c>] (kernel_init_freeable+0xfc/0x1c8) from [<c04d26f4>] (kernel_init+0x8/0xe4)
> [    2.557250] [<c04d26f4>] (kernel_init+0x8/0xe4) from [<c00137b0>] (ret_from_fork+0x14/0x24)

This is exactly the sort of thing which should not ever existed in the first
place...
The code in omap_twl.c, especially the omap3_twl_set_sr_bit() function is
executed in .init_late of the board. If the twl stack is not up by then we are
going to have issues.
Right now I don't see how to solve this (the call chain is related to
smartreflex) but IMHO we should not have these 'random' twl_write calls spread
across the kernel without integrating them to the twl stack in a proper
manner. What I mean is that we should only have twl_* calls from drivers,
which has been created by the twl-core MFD core.

-- 
Péter
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