Date:	Mon, 13 Jul 2015 12:03:44 -0500
From:	Michael Welling <mwelling@...e.org>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Tony Lindgren <tony@...mide.com>,
	Pali Rohár <pali.rohar@...il.com>,
	Pavel Machek <pavel@....cz>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Nishanth Menon <nm@...com>, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: linux 4.2-rc1 broken Nokia N900

On Mon, Jul 13, 2015 at 10:09:21AM +0200, Sebastian Reichel wrote:
> [+cc Michael Welling <mwelling@...e.org>, author of all omap-spi patches between 4.1 and 4.2-rc1]
> 
> Hi,
> 
> On Sun, Jul 12, 2015 at 11:44:25PM -0700, Tony Lindgren wrote:
> > * Pali Rohár <pali.rohar@...il.com> [150711 05:07]:
> > > Hello,
> > > 
> > > now I tested 4.2-rc1 release on Nokia N900 and couple of drivers are
> > > broken and cause kernel oops...
> > > 
> > > Basically wifi, touchscreen and rtc drivers not working...
> > > 
> > > Here are some relevant snippets form dmesg:
> > > 
> > > [   13.933959] Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa09802c
> > > [   13.940490] pgd = cfb38000
> > > [   13.946594] [fa09802c] *pgd=48011452(bad)
> > > [   13.952758] Internal error: : 1028 [#1] PREEMPT ARM
> > > [   13.958862] Modules linked in: tsc2005(+) omap_sham twl4030_wdt omap_wdt
> > > [   13.965332] CPU: 0 PID: 183 Comm: modprobe Not tainted 4.2.0-rc1+ #363
> > > [   13.971801] Hardware name: Nokia RX-51 board
> > > [   13.978302] task: cf572300 ti: cb1f2000 task.ti: cb1f2000
> > > [   13.984924] PC is at omap2_mcspi_set_cs+0x44/0x4c

Here is the disassembly of the omap2_mcspi_set_cs function from my compiler:
00000040 <omap2_mcspi_set_cs>:
      40:       e2803e25        add     r3, r0, #592    ; 0x250
      44:       e5902258        ldr     r2, [r0, #600]  ; 0x258
      48:       e1d330b2        ldrh    r3, [r3, #2]
      4c:       e3130004        tst     r3, #4
      50:       12211001        eorne   r1, r1, #1
      54:       e3520000        cmp     r2, #0
      58:       012fff1e        bxeq    lr
      5c:       e5923018        ldr     r3, [r2, #24]
      60:       e3510000        cmp     r1, #0
      64:       13c33601        bicne   r3, r3, #1048576        ; 0x100000
      68:       03833601        orreq   r3, r3, #1048576        ; 0x100000
      6c:       e5823018        str     r3, [r2, #24]
      70:       e5902258        ldr     r2, [r0, #600]  ; 0x258
      74:       e5922000        ldr     r2, [r2]
      78:       e582302c        str     r3, [r2, #44]   ; 0x2c
      7c:       e5903258        ldr     r3, [r0, #600]  ; 0x258
      80:       e5933000        ldr     r3, [r3]
      84:       e593202c        ldr     r2, [r3, #44]   ; 0x2c
      88:       e12fff1e        bx      lr

The omap2_mcspi_set_cs function is being called before the controller_state is
initialized in omap2_mcspi_setup.

That is why there is a conditional checking if controller_state is NULL.

Perhaps the controller_state is uninitialized but has garbage instead of NULL
causing the data abort.

Though that does not make much sense because a similar check in the setup function
did not cause a data abort in the past.

Not sure what is going wrong here.

Could you do a objdump with the compiler you are using?

> > > [   13.991485] LR is at spi_set_cs+0x5c/0x60
> > > [   13.997985] pc : [<c02bd3ac>]    lr : [<c02baecc>]    psr: 20000013
> > > [   13.997985] sp : cb1f3dd0  ip : 00000001  fp : 00000004
> > > [   14.011260] r10: cfce5be8  r9 : 00000fff  r8 : c0654f98
> > > [   14.017913] r7 : 00000000  r6 : 00000000  r5 : 00000000  r4 : 00000000
> > > [   14.024505] r3 : 200103dc  r2 : fa098000  r1 : 00000001  r0 : cf09bc00
> > > [   14.031036] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
> > > [   14.037689] Control: 10c5387d  Table: 8fb38019  DAC: 00000015
> > > [   14.044403] Process modprobe (pid: 183, stack limit = 0xcb1f2210)
> > > [   14.051300] Stack: (0xcb1f3dd0 to 0xcb1f4000)
> > > [   14.058105] 3dc0:                                     cf09bc00 c02bafa4 cf09bc00 cf09bc00
> > > [   14.065277] 3de0: bf013444 bf01254c cf0e2230 cf0e2230 00000001 c0654f98 00000fff 00000fff
> > > [   14.072570] 3e00: 00000008 00000002 00000118 00001f40 00000031 cf09bc00 ffffffed bf013444
> > > [   14.080078] 3e20: 00000031 c0654f98 cb1f2000 00000000 00000000 c02bb5c0 cf09bc00 00000000
> > > [   14.087738] 3e40: bf013454 c027a2f4 00000000 cf09bc00 bf013454 bf013454 00000000 c027a594
> > > [   14.095367] 3e60: 00000000 cf09bc00 cf09bc34 c027a60c bf013454 cb1f3e80 c027a5ac c0278ec8
> > > [   14.102935] 3e80: cf972c4c cf09d630 bf013454 bf013454 cbb55300 c06848d8 00000000 c0279c84
> > > [   14.110473] 3ea0: bf01327c bf01327d 00000000 bf013454 cb889180 00000000 c0654f98 c027b0c8
> > > [   14.117980] 3ec0: 00000000 bf015000 cb889180 c00095b0 0040003e cfe6a080 0040003f 00000000
> > > [   14.125457] 3ee0: 00080000 cfcf9000 cb1f2000 60000013 0040003e cbf1bbc0 00000000 00000001
> > > [   14.132843] 3f00: bf0134cc cb1f2000 bf0134c0 cb1f3f58 00000000 c04352d0 cf801f00 000000d0
> > > [   14.140136] 3f20: bf0134c0 bf0134c0 0000416c cb889040 00000080 c000ebe4 cb1f2000 c0089f68
> > > [   14.147308] 3f40: bf0134c0 cbf1bc00 001a9193 0000416c 001f8d20 c008ab30 d0b10000 0000416c
> > > [   14.154571] 3f60: d0b1267c d0b1252b d0b13514 000016c0 00001ad0 00000000 00000000 00000000
> > > [   14.161865] 3f80: 0000001f 00000020 00000017 00000014 00000012 00000000 00201208 00000000
> > > [   14.169097] 3fa0: 00000000 c000ea60 00201208 00000000 001f8d20 0000416c 001a9193 00000000
> > > [   14.176177] 3fc0: 00201208 00000000 00000000 00000080 00208c20 001a9193 bee09e98 00000000
> > > [   14.183197] 3fe0: b6f742b4 bee09ae4 000153f0 000093e4 60000010 001f8d20 72757463 69665f65
> > > [   14.190277] [<c02bd3ac>] (omap2_mcspi_set_cs) from [<c02baecc>] (spi_set_cs+0x5c/0x60)
> > > [   14.197479] [<c02baecc>] (spi_set_cs) from [<c02bafa4>] (spi_setup+0xd4/0x10c)
> > > [   14.204833] [<c02bafa4>] (spi_setup) from [<bf01254c>] (tsc2005_probe+0x104/0x484 [tsc2005])
> > > [   14.212249] [<bf01254c>] (tsc2005_probe [tsc2005]) from [<c02bb5c0>] (spi_drv_probe+0x50/0x6c)
> > > [   14.219818] [<c02bb5c0>] (spi_drv_probe) from [<c027a2f4>] (really_probe+0xd4/0x230)
> > > [   14.227478] [<c027a2f4>] (really_probe) from [<c027a594>] (driver_probe_device+0x30/0x48)
> > > [   14.235290] [<c027a594>] (driver_probe_device) from [<c027a60c>] (__driver_attach+0x60/0x84)
> > > [   14.243286] [<c027a60c>] (__driver_attach) from [<c0278ec8>] (bus_for_each_dev+0x50/0x84)
> > > [   14.251281] [<c0278ec8>] (bus_for_each_dev) from [<c0279c84>] (bus_add_driver+0xcc/0x1e0)
> > > [   14.259246] [<c0279c84>] (bus_add_driver) from [<c027b0c8>] (driver_register+0x9c/0xe0)
> > > [   14.267272] [<c027b0c8>] (driver_register) from [<c00095b0>] (do_one_initcall+0x100/0x1b0)
> > > [   14.275421] [<c00095b0>] (do_one_initcall) from [<c0089f68>] (do_init_module+0x58/0x1bc)
> > > [   14.283477] [<c0089f68>] (do_init_module) from [<c008ab30>] (SyS_init_module+0x54/0x64)
> > > [   14.291412] [<c008ab30>] (SyS_init_module) from [<c000ea60>] (ret_fast_syscall+0x0/0x3c)
> > > [   14.299407] Code: e5823018 e5902188 e5922000 e582302c (e592302c) 
> > > [   14.307403] ---[ end trace d21553dcaefcb5ac ]---
> > 
> > That seems to be a regression with the SPI driver. Care to git bisect it?
> > It's probably one of the following commits:
> > 
> > $ git log --pretty=oneline v4.1..v4.2-rc2 drivers/spi/spi-omap2-mcspi.c
> >
> > Looks like just modprobe tsc2005 is enough to reproduce it.
> 
> mh omap2_mcspi_set_cs has been introduced in this range
> (ddcad7e9068) and from the commit message it seems to be
> a fix for the first commit (b28cb9414d) in this range.
> 
> Just looking at the commit log, I sugest starting with testing if
> ddcad7e9068 is affected and if b28cb9414d~1 is not affected.
> 
> -- Sebastian


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