linux-kernel - Re: [PATCH] drm/msm/dp: reset drm_dev to NULL at dp_display

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Message-ID: <fb4310fd-61b1-08ab-c1fb-ed530684a390@linaro.org>
Date:   Wed, 22 Jun 2022 21:14:07 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org
Cc:     quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: reset drm_dev to NULL at dp_display_unbind()

On 22/06/2022 19:54, Kuogee Hsieh wrote:
> During msm initialize phase, dp_display_unbind() will be called to undo
> initializations had been done by dp_display_bind() previously if there is
> error happen at msm_drm_bind. Under this kind of circumstance, drm_device
> may not be populated completed which causes system crash at drm_dev_dbg().
> This patch reset drm_dev to NULL so that following drm_dev_dbg() will not
> refer to any internal fields of drm_device to prevent system from crashing.
> Below are panic stack trace,
> 
> [   53.584904] Unable to handle kernel paging request at virtual address 0000000070018001
> .
> [   53.702212] Hardware name: Qualcomm Technologies, Inc. sc7280 CRD platform (rev5+) (DT)
> [   53.710445] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   53.717596] pc : string_nocheck+0x1c/0x64
> [   53.721738] lr : string+0x54/0x60
> [   53.725162] sp : ffffffc013d6b650
> [   53.728590] pmr_save: 000000e0
> [   53.731743] x29: ffffffc013d6b650 x28: 0000000000000002 x27: 0000000000ffffff
> [   53.739083] x26: ffffffc013d6b710 x25: ffffffd07a066ae0 x24: ffffffd07a419f97
> [   53.746420] x23: ffffffd07a419f99 x22: ffffff81fef360d4 x21: ffffff81fef364d4
> [   53.753760] x20: ffffffc013d6b6f8 x19: ffffffd07a06683c x18: 0000000000000000
> [   53.761093] x17: 4020386678302f30 x16: 00000000000000b0 x15: ffffffd0797523c8
> [   53.768429] x14: 0000000000000004 x13: ffff0000ffffff00 x12: ffffffd07a066b2c
> [   53.775780] x11: 0000000000000000 x10: 000000000000013c x9 : 0000000000000000
> [   53.783117] x8 : ffffff81fef364d4 x7 : 0000000000000000 x6 : 0000000000000000
> [   53.790445] x5 : 0000000000000000 x4 : ffff0a00ffffff04 x3 : ffff0a00ffffff04
> [   53.797783] x2 : 0000000070018001 x1 : ffffffffffffffff x0 : ffffff81fef360d4
> [   53.805136] Call trace:
> [   53.807667]  string_nocheck+0x1c/0x64
> [   53.811439]  string+0x54/0x60
> [   53.814498]  vsnprintf+0x374/0x53c
> [   53.818009]  pointer+0x3dc/0x40c
> [   53.821340]  vsnprintf+0x398/0x53c
> [   53.824854]  vscnprintf+0x3c/0x88
> [   53.828274]  __trace_array_vprintk+0xcc/0x2d4
> [   53.832768]  trace_array_printk+0x8c/0xb4
> [   53.836900]  drm_trace_printf+0x74/0x9c
> [   53.840875]  drm_dev_dbg+0xfc/0x1b8
> [   53.844480]  dp_pm_suspend+0x70/0xf8
> [   53.848164]  dpm_run_callback+0x60/0x1a0
> [   53.852222]  __device_suspend+0x304/0x3f4
> [   53.856363]  dpm_suspend+0xf8/0x3a8
> [   53.859959]  dpm_suspend_start+0x8c/0xc0
> 
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 2b72639..02fff70 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -316,6 +316,8 @@ static void dp_display_unbind(struct device *dev, struct device *master,
>   
>   	dp_power_client_deinit(dp->power);
>   	dp_aux_unregister(dp->aux);
> +	dp->drm_dev = NULL;
> +	dp->aux->drm_dev = NULL;
>   	priv->dp[dp->id] = NULL;
>   }
>   


-- 
With best wishes
Dmitry