linux-kernel - [PATCH 2/2] drm: bridge: adv7511: unregister cec i2c device after cec adapter

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Date:   Sat, 19 Mar 2022 15:59:39 +0100
From:   Alvin Šipraga <alvin@...s.dk>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Archit Taneja <architt@...eaurora.org>
Cc:     Alvin Šipraga <alsi@...g-olufsen.dk>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] drm: bridge: adv7511: unregister cec i2c device after cec adapter

From: Alvin Šipraga <alsi@...g-olufsen.dk>

cec_unregister_adapter() assumes that the underlying adapter ops are
callable. For example, if the CEC adapter currently has a valid physical
address, then the unregistration procedure will invalidate the physical
address by setting it to f.f.f.f. Whence the following kernel oops
observed after removing the adv7511 module:

    Unable to handle kernel execution of user memory at virtual address 0000000000000000
    Internal error: Oops: 86000004 [#1] PREEMPT_RT SMP
    Call trace:
     0x0
     adv7511_cec_adap_log_addr+0x1ac/0x1c8 [adv7511]
     cec_adap_unconfigure+0x44/0x90 [cec]
     __cec_s_phys_addr.part.0+0x68/0x230 [cec]
     __cec_s_phys_addr+0x40/0x50 [cec]
     cec_unregister_adapter+0xb4/0x118 [cec]
     adv7511_remove+0x60/0x90 [adv7511]
     i2c_device_remove+0x34/0xe0
     device_release_driver_internal+0x114/0x1f0
     driver_detach+0x54/0xe0
     bus_remove_driver+0x60/0xd8
     driver_unregister+0x34/0x60
     i2c_del_driver+0x2c/0x68
     adv7511_exit+0x1c/0x67c [adv7511]
     __arm64_sys_delete_module+0x154/0x288
     invoke_syscall+0x48/0x100
     el0_svc_common.constprop.0+0x48/0xe8
     do_el0_svc+0x28/0x88
     el0_svc+0x1c/0x50
     el0t_64_sync_handler+0xa8/0xb0
     el0t_64_sync+0x15c/0x160
    Code: bad PC value
    ---[ end trace 0000000000000000 ]---

Protect against this scenario by unregistering i2c_cec after
unregistering the CEC adapter. Duly disable the CEC clock afterwards
too.

Fixes: 3b1b975003e4 ("drm: adv7511/33: add HDMI CEC support")
Signed-off-by: Alvin Šipraga <alsi@...g-olufsen.dk>
---
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index f8e5da148599..2628f1abe413 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -1314,9 +1314,6 @@ static int adv7511_remove(struct i2c_client *i2c)
 {
 	struct adv7511 *adv7511 = i2c_get_clientdata(i2c);
 
-	i2c_unregister_device(adv7511->i2c_cec);
-	clk_disable_unprepare(adv7511->cec_clk);
-
 	adv7511_uninit_regulators(adv7511);
 
 	drm_bridge_remove(&adv7511->bridge);
@@ -1324,6 +1321,8 @@ static int adv7511_remove(struct i2c_client *i2c)
 	adv7511_audio_exit(adv7511);
 
 	cec_unregister_adapter(adv7511->cec_adap);
+	i2c_unregister_device(adv7511->i2c_cec);
+	clk_disable_unprepare(adv7511->cec_clk);
 
 	i2c_unregister_device(adv7511->i2c_packet);
 	i2c_unregister_device(adv7511->i2c_edid);
-- 
2.35.1