drm/amd/display: fix null-pointer dereference on edid reading

Use i2c adapter when there isn't aux_mode in dc_link to fix a
null-pointer derefence that happens when running
igt@kms_force_connector_basic in a system with DCN2.1 and HDMI connector
detected as below:

[  +0.178146] BUG: kernel NULL pointer dereference, address: 00000000000004c0
[  +0.000010] #PF: supervisor read access in kernel mode
[  +0.000005] #PF: error_code(0x0000) - not-present page
[  +0.000004] PGD 0 P4D 0
[  +0.000006] Oops: 0000 [#1] PREEMPT SMP NOPTI
[  +0.000006] CPU: 15 PID: 2368 Comm: kms_force_conne Not tainted 6.5.0-asdn+ #152
[  +0.000005] Hardware name: HP HP ENVY x360 Convertible 13-ay1xxx/8929, BIOS F.01 07/14/2021
[  +0.000004] RIP: 0010:i2c_transfer+0xd/0x100
[  +0.000011] Code: ea fc ff ff 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 54 55 53 <48> 8b 47 10 48 89 fb 48 83 38 00 0f 84 b3 00 00 00 83 3d 2f 80 16
[  +0.000004] RSP: 0018:ffff9c4f89c0fad0 EFLAGS: 00010246
[  +0.000005] RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000000080
[  +0.000003] RDX: 0000000000000002 RSI: ffff9c4f89c0fb20 RDI: 00000000000004b0
[  +0.000003] RBP: ffff9c4f89c0fb80 R08: 0000000000000080 R09: ffff8d8e0b15b980
[  +0.000003] R10: 00000000000380e0 R11: 0000000000000000 R12: 0000000000000080
[  +0.000002] R13: 0000000000000002 R14: ffff9c4f89c0fb0e R15: ffff9c4f89c0fb0f
[  +0.000004] FS:  00007f9ad2176c40(0000) GS:ffff8d90fe9c0000(0000) knlGS:0000000000000000
[  +0.000003] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  +0.000004] CR2: 00000000000004c0 CR3: 0000000121bc4000 CR4: 0000000000750ee0
[  +0.000003] PKRU: 55555554
[  +0.000003] Call Trace:
[  +0.000006]  <TASK>
[  +0.000006]  ? __die+0x23/0x70
[  +0.000011]  ? page_fault_oops+0x17d/0x4c0
[  +0.000008]  ? preempt_count_add+0x6e/0xa0
[  +0.000008]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000011]  ? exc_page_fault+0x7f/0x180
[  +0.000009]  ? asm_exc_page_fault+0x26/0x30
[  +0.000013]  ? i2c_transfer+0xd/0x100
[  +0.000010]  drm_do_probe_ddc_edid+0xc2/0x140 [drm]
[  +0.000067]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000006]  ? _drm_do_get_edid+0x97/0x3c0 [drm]
[  +0.000043]  ? __pfx_drm_do_probe_ddc_edid+0x10/0x10 [drm]
[  +0.000042]  edid_block_read+0x3b/0xd0 [drm]
[  +0.000043]  _drm_do_get_edid+0xb6/0x3c0 [drm]
[  +0.000041]  ? __pfx_drm_do_probe_ddc_edid+0x10/0x10 [drm]
[  +0.000043]  drm_edid_read_custom+0x37/0xd0 [drm]
[  +0.000044]  amdgpu_dm_connector_mode_valid+0x129/0x1d0 [amdgpu]
[  +0.000153]  drm_connector_mode_valid+0x3b/0x60 [drm_kms_helper]
[  +0.000000]  __drm_helper_update_and_validate+0xfe/0x3c0 [drm_kms_helper]
[  +0.000000]  ? amdgpu_dm_connector_get_modes+0xb6/0x520 [amdgpu]
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  drm_helper_probe_single_connector_modes+0x2ab/0x540 [drm_kms_helper]
[  +0.000000]  status_store+0xb2/0x1f0 [drm]
[  +0.000000]  kernfs_fop_write_iter+0x136/0x1d0
[  +0.000000]  vfs_write+0x24d/0x440
[  +0.000000]  ksys_write+0x6f/0xf0
[  +0.000000]  do_syscall_64+0x60/0xc0
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  ? syscall_exit_to_user_mode+0x2b/0x40
[  +0.000000]  ? srso_alias_return_thunk+0x5/0x7f
[  +0.000000]  ? do_syscall_64+0x6c/0xc0
[  +0.000000]  ? do_syscall_64+0x6c/0xc0
[  +0.000000]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[  +0.000000] RIP: 0033:0x7f9ad46b4b00
[  +0.000000] Code: 40 00 48 8b 15 19 b3 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d e1 3a 0e 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89
[  +0.000000] RSP: 002b:00007ffcbd3bd6d8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
[  +0.000000] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9ad46b4b00
[  +0.000000] RDX: 0000000000000002 RSI: 00007f9ad48a7417 RDI: 0000000000000009
[  +0.000000] RBP: 0000000000000002 R08: 0000000000000064 R09: 0000000000000000
[  +0.000000] R10: 0000000000000000 R11: 0000000000000202 R12: 00007f9ad48a7417
[  +0.000000] R13: 0000000000000009 R14: 00007ffcbd3bd760 R15: 0000000000000001
[  +0.000000]  </TASK>
[  +0.000000] Modules linked in: ctr ccm rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device cmac algif_hash algif_skcipher af_alg bnep btusb btrtl btbcm btintel btmtk bluetooth uvcvideo videobuf2_vmalloc sha3_generic videobuf2_memops uvc jitterentropy_rng videobuf2_v4l2 videodev drbg videobuf2_common ansi_cprng mc ecdh_generic ecc qrtr binfmt_misc hid_sensor_accel_3d hid_sensor_magn_3d hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer kfifo_buf industrialio snd_ctl_led joydev hid_sensor_iio_common rtw89_8852ae rtw89_8852a rtw89_pci snd_hda_codec_realtek rtw89_core snd_hda_codec_generic intel_rapl_msr ledtrig_audio intel_rapl_common snd_hda_codec_hdmi mac80211 snd_hda_intel snd_intel_dspcfg kvm_amd snd_hda_codec snd_soc_dmic snd_acp3x_rn snd_acp3x_pdm_dma libarc4 snd_hwdep snd_soc_core kvm snd_hda_core cfg80211 snd_pci_acp6x snd_pcm nls_ascii snd_timer hp_wmi snd_pci_acp5x nls_cp437 snd_rn_pci_acp3x ucsi_acpi sparse_keymap ccp snd platform_profile snd_acp_config typec_ucsi irqbypass vfat sp5100_tco
[  +0.000000]  snd_soc_acpi fat rapl pcspkr wmi_bmof roles rfkill rng_core snd_pci_acp3x soundcore k10temp watchdog typec battery ac amd_pmc acpi_tad button hid_sensor_hub hid_multitouch evdev serio_raw msr parport_pc ppdev lp parport fuse loop efi_pstore configfs ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 btrfs blake2b_generic dm_crypt dm_mod efivarfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx libcrc32c crc32c_generic xor raid6_pq raid1 raid0 multipath linear md_mod amdgpu amdxcp i2c_algo_bit drm_ttm_helper ttm crc32_pclmul crc32c_intel drm_exec gpu_sched drm_suballoc_helper nvme ghash_clmulni_intel drm_buddy drm_display_helper sha512_ssse3 nvme_core ahci xhci_pci sha512_generic hid_generic xhci_hcd libahci rtsx_pci_sdmmc t10_pi i2c_hid_acpi drm_kms_helper i2c_hid mmc_core libata aesni_intel crc64_rocksoft_generic crypto_simd amd_sfh crc64_rocksoft scsi_mod usbcore cryptd crc_t10dif cec drm crct10dif_generic hid rtsx_pci crct10dif_pclmul scsi_common rc_core crc64 i2c_piix4
[  +0.000000]  usb_common crct10dif_common video wmi
[  +0.000000] CR2: 00000000000004c0
[  +0.000000] ---[ end trace 0000000000000000 ]---

Fixes: 0e859faf ("drm/amd/display: Remove unwanted drm edid references")
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -6534,10 +6534,15 @@ amdgpu_dm_connector_late_register(struct drm_connector *connector)
 static void amdgpu_dm_connector_funcs_force(struct drm_connector *connector)
 {
 	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
-	struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(connector);
 	struct dc_link *dc_link = aconnector->dc_link;
 	struct dc_sink *dc_em_sink = aconnector->dc_em_sink;
 	struct edid *edid;
+	struct i2c_adapter *ddc;
+
+	if (dc_link->aux_mode)
+		ddc = &aconnector->dm_dp_aux.aux.ddc;
+	else
+		ddc = &aconnector->i2c->base;
 
 	/*
 	 * Note: drm_get_edid gets edid in the following order:
@@ -6545,7 +6550,7 @@ static void amdgpu_dm_connector_funcs_force(struct drm_connector *connector)
 	 * 2) firmware EDID if set via edid_firmware module parameter
 	 * 3) regular DDC read.
 	 */
-	edid = drm_get_edid(connector, &amdgpu_connector->ddc_bus->aux.ddc);
+	edid = drm_get_edid(connector, ddc);
 	if (!edid) {
 		DRM_ERROR("No EDID found on connector: %s.\n", connector->name);
 		return;
@@ -6586,12 +6591,18 @@ static int get_modes(struct drm_connector *connector)
 static void create_eml_sink(struct amdgpu_dm_connector *aconnector)
 {
 	struct drm_connector *connector = &aconnector->base;
-	struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(&aconnector->base);
+	struct dc_link *dc_link = aconnector->dc_link;
 	struct dc_sink_init_data init_params = {
 			.link = aconnector->dc_link,
 			.sink_signal = SIGNAL_TYPE_VIRTUAL
 	};
 	struct edid *edid;
+	struct i2c_adapter *ddc;
+
+	if (dc_link->aux_mode)
+		ddc = &aconnector->dm_dp_aux.aux.ddc;
+	else
+		ddc = &aconnector->i2c->base;
 
 	/*
 	 * Note: drm_get_edid gets edid in the following order:
@@ -6599,7 +6610,7 @@ static void create_eml_sink(struct amdgpu_dm_connector *aconnector)
 	 * 2) firmware EDID if set via edid_firmware module parameter
 	 * 3) regular DDC read.
 	 */
-	edid = drm_get_edid(connector, &amdgpu_connector->ddc_bus->aux.ddc);
+	edid = drm_get_edid(connector, ddc);
 	if (!edid) {
 		DRM_ERROR("No EDID found on connector: %s.\n", connector->name);
 		return;