From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	=?UTF-8?q?Timur=20Krist=C3=B3f?= <timur.kristof@gmail.com>,
	Harry Wentland <harry.wentland@amd.com>,
	Mario Limonciello <superm1@kernel.org>,
	Alex Hung <alex.hung@amd.com>,
	Aurabindo Pillai <aurabindo.pillai@amd.com>,
	ChiaHsuan Chung <chiahsuan.chung@amd.com>,
	Roman Li <roman.li@amd.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.19 719/781] drm/amd/display: Fix dc_link NULL handling in HPD init
Date: Tue, 24 Feb 2026 17:23:48 -0800
Message-ID: <20260225012417.373885962@linuxfoundation.org>
In-Reply-To: <20260225012359.695468795@linuxfoundation.org>
References: <20260225012359.695468795@linuxfoundation.org>
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6.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>

[ Upstream commit 226a40c06a183abaeb7529a4f54d6c203bd14407 ]

amdgpu_dm_hpd_init() may see connectors without a valid dc_link.

The code already checks dc_link for the polling decision, but later
unconditionally dereferences it when setting up HPD interrupts.

Assign dc_link early and skip connectors where it is NULL.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c:940 amdgpu_dm_hpd_init()
error: we previously assumed 'dc_link' could be null (see line 931)

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_irq.c
    923                 /*
    924                  * Analog connectors may be hot-plugged unlike other connector
    925                  * types that don't support HPD. Only poll analog connectors.
    926                  */
    927                 use_polling |=
    928                         amdgpu_dm_connector->dc_link &&
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The patch adds this NULL check but hopefully it can be removed

    929                         dc_connector_supports_analog(amdgpu_dm_connector->dc_link->link_id.id);
    930
    931                 dc_link = amdgpu_dm_connector->dc_link;

dc_link assigned here.

    932
    933                 /*
    934                  * Get a base driver irq reference for hpd ints for the lifetime
    935                  * of dm. Note that only hpd interrupt types are registered with
    936                  * base driver; hpd_rx types aren't. IOW, amdgpu_irq_get/put on
    937                  * hpd_rx isn't available. DM currently controls hpd_rx
    938                  * explicitly with dc_interrupt_set()
    939                  */
--> 940                 if (dc_link->irq_source_hpd != DC_IRQ_SOURCE_INVALID) {
                            ^^^^^^^^^^^^^^^^^^^^^^^ If it's NULL then we are trouble because we dereference it here.

    941                         irq_type = dc_link->irq_source_hpd - DC_IRQ_SOURCE_HPD1;
    942                         /*
    943                          * TODO: There's a mismatch between mode_info.num_hpd
    944                          * and what bios reports as the # of connectors with hpd

Fixes: 4562236b3bc0 ("drm/amd/dc: Add dc display driver (v2)")
Cc: Timur Kristóf <timur.kristof@gmail.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Mario Limonciello <superm1@kernel.org>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: ChiaHsuan Chung <chiahsuan.chung@amd.com>
Cc: Roman Li <roman.li@amd.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
index e7b0928bd3db7..5948e2a6219e3 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
@@ -919,16 +919,15 @@ void amdgpu_dm_hpd_init(struct amdgpu_device *adev)
 			continue;
 
 		amdgpu_dm_connector = to_amdgpu_dm_connector(connector);
+		dc_link = amdgpu_dm_connector->dc_link;
+		if (!dc_link)
+			continue;
 
 		/*
 		 * Analog connectors may be hot-plugged unlike other connector
 		 * types that don't support HPD. Only poll analog connectors.
 		 */
-		use_polling |=
-			amdgpu_dm_connector->dc_link &&
-			dc_connector_supports_analog(amdgpu_dm_connector->dc_link->link_id.id);
-
-		dc_link = amdgpu_dm_connector->dc_link;
+		use_polling |= dc_connector_supports_analog(dc_link->link_id.id);
 
 		/*
 		 * Get a base driver irq reference for hpd ints for the lifetime
-- 
2.51.0