Re: [PATCH v2] drm/msm: another fix for the headless Adreno GPU

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 04/01/2023 20:15, Rob Clark wrote:
> On Wed, Jan 4, 2023 at 10:09 AM Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > On 1/3/2023 7:51 AM, Dmitry Baryshkov wrote:
> > > Fix another oops reproducible when rebooting the board with the Adreno
> > > GPU wokring in the headless mode (e.g. iMX platforms).
> > wokring ---> working
> > > Unable to handle kernel NULL pointer dereference at virtual address 00000000 when read
> > > [00000000] *pgd=74936831, *pte=00000000, *ppte=00000000
> > > Internal error: Oops: 17 [#1] ARM
> > > CPU: 0 PID: 51 Comm: reboot Not tainted 6.2.0-rc1-dirty #11
> > > Hardware name: Freescale i.MX53 (Device Tree Support)
> > > PC is at msm_atomic_commit_tail+0x50/0x970
> > > LR is at commit_tail+0x9c/0x188
> > > pc : [<c06aa430>]    lr : [<c067a214>]    psr: 600e0013
> > > sp : e0851d30  ip : ee4eb7eb  fp : 00090acc
> > > r10: 00000058  r9 : c2193014  r8 : c4310000
> > > r7 : c4759380  r6 : 07bef61d  r5 : 00000000  r4 : 00000000
> > > r3 : c44cc440  r2 : 00000000  r1 : 00000000  r0 : 00000000
> > > Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> > > Control: 10c5387d  Table: 74910019  DAC: 00000051
> > > Register r0 information: NULL pointer
> > > Register r1 information: NULL pointer
> > > Register r2 information: NULL pointer
> > > Register r3 information: slab kmalloc-1k start c44cc400 pointer offset 64 size 1024
> > > Register r4 information: NULL pointer
> > > Register r5 information: NULL pointer
> > > Register r6 information: non-paged memory
> > > Register r7 information: slab kmalloc-128 start c4759380 pointer offset 0 size 128
> > > Register r8 information: slab kmalloc-2k start c4310000 pointer offset 0 size 2048
> > > Register r9 information: non-slab/vmalloc memory
> > > Register r10 information: non-paged memory
> > > Register r11 information: non-paged memory
> > > Register r12 information: non-paged memory
> > > Process reboot (pid: 51, stack limit = 0xc80046d9)
> > > Stack: (0xe0851d30 to 0xe0852000)
> > > 1d20:                                     c4759380 fbd77200 000005ff 002b9c70
> > > 1d40: c4759380 c4759380 00000000 07bef61d 00000600 c0d6fe7c c2193014 00000058
> > > 1d60: 00090acc c067a214 00000000 c4759380 c4310000 00000000 c44cc854 c067a89c
> > > 1d80: 00000000 00000000 00000000 c4310468 00000000 c4759380 c4310000 c4310468
> > > 1da0: c4310470 c0643258 c4759380 00000000 00000000 c0c4ee24 00000000 c44cc810
> > > 1dc0: 00000000 c0c4ee24 00000000 c44cc810 00000000 0347d2a8 e0851e00 e0851e00
> > > 1de0: c4759380 c067ad20 c4310000 00000000 c44cc810 c27f8718 c44cc854 c067adb8
> > > 1e00: c4933000 00000002 00000001 00000000 00000000 c2130850 00000000 c2130854
> > > 1e20: c25fc488 00000000 c0ff162c 00000000 00000001 00000002 00000000 00000000
> > > 1e40: c43102c0 c43102c0 00000000 0347d2a8 c44cc810 c44cc814 c2133da8 c06d1a60
> > > 1e60: 00000000 00000000 00079028 c2012f24 fee1dead c4933000 00000058 c01431e4
> > > 1e80: 01234567 c0143a20 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1ea0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1ec0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1ee0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1f00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1f20: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1f40: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1f60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > 1f80: 00000000 00000000 00000000 0347d2a8 00000002 00000004 00000078 00000058
> > > 1fa0: c010028c c0100060 00000002 00000004 fee1dead 28121969 01234567 00079028
> > > 1fc0: 00000002 00000004 00000078 00000058 0002fdc5 00000000 00000000 00090acc
> > > 1fe0: 00000058 becc9c64 b6e97e05 b6e0e5f6 600e0030 fee1dead 00000000 00000000
> > >    msm_atomic_commit_tail from commit_tail+0x9c/0x188
> > >    commit_tail from drm_atomic_helper_commit+0x160/0x188
> > >    drm_atomic_helper_commit from drm_atomic_commit+0xac/0xe0
> > >    drm_atomic_commit from drm_atomic_helper_disable_all+0x1b0/0x1c0
> > >    drm_atomic_helper_disable_all from drm_atomic_helper_shutdown+0x88/0x140
> > >    drm_atomic_helper_shutdown from device_shutdown+0x16c/0x240
> > >    device_shutdown from kernel_restart+0x38/0x90
> > >    kernel_restart from __do_sys_reboot+0x174/0x224
> > >    __do_sys_reboot from ret_fast_syscall+0x0/0x1c
> > > Exception stack(0xe0851fa8 to 0xe0851ff0)
> > > 1fa0:                   00000002 00000004 fee1dead 28121969 01234567 00079028
> > > 1fc0: 00000002 00000004 00000078 00000058 0002fdc5 00000000 00000000 00090acc
> > > 1fe0: 00000058 becc9c64 b6e97e05 b6e0e5f6
> > > Code: 15922088 1184421c e1500003 1afffff8 (e5953000)
> > > ---[ end trace 0000000000000000 ]---
> > >
> > > Fixes: 0a58d2ae572a ("drm/msm: Make .remove and .shutdown HW shutdown consistent")
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> >
> > How is this null pointer hitting?
> >
> > priv->kms is assigned in the msm_drm_init() which happens in the bind.

The headless A200 (e.g. on i.MX53) doesn't have KMS. This has been a 
frequent case causing issues in .shutdown path.

> I think we want to solve this higher up.. hitting atomic commit path
> on a device which has no kms resources (planes, CRTCs, etc) seems
> pretty wrong

Fine with me. Would it be better to skip a call to 
drm_atomic_helper_shutdown() if there is no drm->kms?

> BR,
> -R
>
> > Only then we register the dri card for the commit which means commit
> > cannot come before that.
> >
> > So, how can this sequence be possible?
--
With best wishes
Dmitry