Re: [PATCH RESEND] drm/rockchip: Unregister platform drivers in reverse order

From: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
To: Andy Yan <andyshrk@163.com>
Cc: "Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Sean Paul" <seanpaul@chromium.org>,
	"Jeffy Chen" <jeffy.chen@rock-chips.com>,
	"Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Mark Yao" <markyao0591@gmail.com>,
	kernel@collabora.com, dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND] drm/rockchip: Unregister platform drivers in reverse order
Date: Mon, 12 Aug 2024 23:04:12 +0300	[thread overview]
Message-ID: <31cb347a-1d14-4114-bad3-5e9e4e87bf08@collabora.com> (raw)
In-Reply-To: <3649004a.1f69.191445d79dc.Coremail.andyshrk@163.com>

Hi Andy,

On 8/12/24 5:14 AM, Andy Yan wrote:
> 
> Hi Cristian,
> 
> At 2024-08-08 19:58:02, "Cristian Ciocaltea" <cristian.ciocaltea@collabora.com> wrote:
>> Move rockchip_drm_platform_driver unregistration after its sub-drivers,
>> which ensures all drivers are unregistered in the reverse order used
>> when they were registered.
> 
> Would you please provied some detail information about how to reproduce this
> issue this patch try to fix？Or some kernel log when this issue   triggered。

I submitted this patch while investigating a couple of issues
encountered when tried to reload the rockchipdrm module. 

One was a system freeze, which eventually proved to have a different
root cause and got fixed via [1].  The other one was a lockdep splat
which seems to be caused by the switch to maple tree register cache in
vop2 - I have a regmap workaround, not yet sure that's a proper fix.

As of v6.11-rc1, reloading the module works fine, w/ or w/o this patch
applied (ignoring the above mentioned splat).  But I could only verify
on Rock 3A, hence unregistering the drivers in the correct order should,
at least, eliminate a potential source of unexpected behavior on the
other boards.

Regards,
Cristian

[1]: 9d42c3ee3ce3 ("arm64: dts: rockchip: Add missing power-domains for rk356x vop_mmu")

>> Fixes: 8820b68bd378 ("drm/rockchip: Refactor the component match logic.")
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
>> ---
>> drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> index 44d769d9234d..ca7b07503fbe 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>> @@ -528,10 +528,9 @@ static int __init rockchip_drm_init(void)
>>
>> static void __exit rockchip_drm_fini(void)
>> {
>> -	platform_driver_unregister(&rockchip_drm_platform_driver);
>> -
>> 	platform_unregister_drivers(rockchip_sub_drivers,
>> 				    num_rockchip_sub_drivers);
>> +	platform_driver_unregister(&rockchip_drm_platform_driver);
>> }
>>
>> module_init(rockchip_drm_init);
>>
>> ---
>> base-commit: 1eb586a9782cde8e5091b9de74603e0a8386b09e
>> change-id: 20240702-rk-drm-fix-unreg-9f3f29996a00
>> -- 
>> Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

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