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

[Abhinav Kumar]

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 at intel.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>

How is this null pointer hitting?

priv->kms is assigned in the msm_drm_init() which happens in the bind.

Only then we register the dri card for the commit which means commit 
cannot come before that.

So, how can this sequence be possible?

> ---
> 
> Changes since v1:
> - Moved setting of `async' before the call to trace to fix the
>    uninitialized variable warning
> 
> ---
>   drivers/gpu/drm/msm/msm_atomic.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
> index 1686fbb611fd..d8cded52cabf 100644
> --- a/drivers/gpu/drm/msm/msm_atomic.c
> +++ b/drivers/gpu/drm/msm/msm_atomic.c
> @@ -186,7 +186,12 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
>   	struct msm_kms *kms = priv->kms;
>   	struct drm_crtc *async_crtc = NULL;
>   	unsigned crtc_mask = get_crtc_mask(state);
> -	bool async = kms->funcs->vsync_time &&
> +	bool async;
> +
> +	if (!kms)
> +		return;
> +
> +	async = kms->funcs->vsync_time &&
>   			can_do_async(state, &async_crtc);
>   
>   	trace_msm_atomic_commit_tail_start(async, crtc_mask);