[PATCH 001/001] drivers/gpu/radeon: NULL pointer deference workaround
Christian König
christian.koenig at amd.com
Fri Sep 9 08:15:39 UTC 2016
>> On this motherboard, DP-1 is a single channel 18bit LVDS LCD panel
>> interface and DP-2 is a DVI interface (which I can connect to my
>> monitor if testing this is useful). There are no displayport connectors.
>
> Yeah, but from the driver point of view there are only DP connectors on
> the chip. The LVDS and DVI are probably realized with external DP to
> whatever converter ICs.
>
>
> That would explain why some similar boards have 24bit LVDS and others
> only 18bit LVDS.
It could be that this is actually a configuration we don't support yet
with radeon and/or the display stack.
E.g. that the connector only uses the displayport LVDS lanes, but not
actual the displayport protocol to train those lanes.
Instead it rather expects a fixed training which is configured somewhere
in the BIOS.
Anyway Alex needs to take a look, he knows displayport much better than
I do (and hates it passionately :).
Cheers,
Christian.
Am 08.09.2016 um 13:18 schrieb Mark Fortescue:
> On 08/09/16 11:25, Christian König wrote:
>> Am 08.09.2016 um 11:09 schrieb Mark Fortescue:
>>> Hi Christian,
>>>
>>> Thank you for the feedback.
>>>
>>> On 08/09/16 08:14, Christian König wrote:
>>>> Am 07.09.2016 um 19:38 schrieb Mark Fortescue:
>>>>>
>>>>> On an LV-683 (AMD Dual-core G-T56N) Mini-ITX board, I get a Kernel
>>>>> Oops because Connector 0 (LCD Panel interface) does not have DDC.
>>>>
>>>> I'm not an expert on this, but that is really odd cause even LCD
>>>> Panels
>>>> should have a DDC interface.
>>>>
>>>>>
>>>>> Ubuntu 16.04 LTS Kernel (4.4 series):
>>>>>
>>>>> ...
>>>>> [ 8.262990] [drm] ib test on ring 5 succeeded
>>>>> [ 8.288897] [drm] Radeon Display Connectors
>>>>> [ 8.293175] [drm] Connector 0:
>>>>> [ 8.296252] [drm] DP-1
>>>>
>>>> Especially since the BIOS claims that this is a displayport connector
>>>> and there is no physical way to have a DP without an DDC as far as I
>>>> know.
>>>>
>>>> Please open a bug report on FDO and attach you BIOS image.
>>>
>>> FDO ? I am not familiar with this. Please can you enlighten me.
>>>
>>
>> See here: http://bugs.freedesktop.org/
>>
>>> I do not have a BIOS image so will need some assistance in
>>> understanding what is required here and how I extract the BIOS
>>> information you are after.
>>>
>>
>> Sorry my fault. Mullins is an APU, so you don't have a dedicated video
>> BIOS. As usually I didn't got enough sleep :) But please open up a bug
>> report anyway.
>
> Know the problem of being awake too long :). I will raise a bug.
>
>>
>>> On this motherboard, DP-1 is a single channel 18bit LVDS LCD panel
>>> interface and DP-2 is a DVI interface (which I can connect to my
>>> monitor if testing this is useful). There are no displayport
>>> connectors.
>>
>> Yeah, but from the driver point of view there are only DP connectors on
>> the chip. The LVDS and DVI are probably realized with external DP to
>> whatever converter ICs.
>>
>
> That would explain why some similar boards have 24bit LVDS and others
> only 18bit LVDS.
>
>>>
>>> On industrial motherboards, I have noticed that it is not uncommon to
>>> hard code the information for the LCD panel into the BIOS so no DDC is
>>> required. In this case, there is no LCD panel connected to the
>>> interface anyway.
>>>
>>
>> That is correct and as far as I know well supported by Radeon, but the
>> crux is there should still be a DDC channel even if there isn't anything
>> attached to it.
>>
>> See with displayport you got four LVDS channels to submit the actual
>> picture and an AUX channel to configure and query the device. The DDC is
>> just represented as certain packets over the AUX channel.
>>
>> If the AUX channel doesn't work or isn't connect then the link training
>> wouldn't be possible as well and so you wouldn't be able to get any
>> picture on the LVDS.
>>
>
> Interesting.
>
>>> See http://www.commell.com.tw/product/SBC/LV-683.HTM for more
>>> information on the board. Looking at the web site, there is a BIOS
>>> image available form Commell if that is of use.
>>
>> Alex clearly needs to take a look on this. I think for the time being
>> you could hack together a patch which just ignores DP connectors during
>> probing if they don't have an associated DDC instead of changing the
>> code everywhere the DDC object is required.
>>
>
> I will try to find the time to look at this in more detail. GPU/DRM is
> not something I have done any real work on in the past so I do not
> know how it all fits together. The overkill on the code changes is the
> result, as that way I don't need to understand where and why the
> helper function (radeon_dp_getsinktype) gets called or what other code
> paths can be executed that could fail.
>
> I will wait for Alex to have a think about it and respond before I do
> any more - that way I can finish the work I am paid to do first :).
>
>> Regards,
>> Christian.
>>
> Regards
> Mark.
>>>
>>>>
>>>> Alex can probably take a look when he's back from vacation.
>>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>>> [ 8.298791] [drm] Encoders:
>>>>> [ 8.301770] [drm] DFP1: INTERNAL_UNIPHY
>>>>> [ 8.305973] [drm] Connector 1:
>>>>> [ 8.309043] [drm] DP-2
>>>>> [ 8.311598] [drm] HPD2
>>>>> [ 8.314169] [drm] DDC: 0x6440 0x6440 0x6444 0x6444 0x6448 0x6448
>>>>> 0x644c 0x644c
>>>>> [ 8.321609] [drm] Encoders:
>>>>> [ 8.324589] [drm] DFP2: INTERNAL_UNIPHY
>>>>> [ 8.328793] [drm] Connector 2:
>>>>> [ 8.331856] [drm] VGA-1
>>>>> [ 8.342947] [drm] DDC: 0x64d8 0x64d8 0x64dc 0x64dc 0x64e0 0x64e0
>>>>> 0x64e4 0x64e4
>>>>> [ 8.350341] [drm] Encoders:
>>>>> [ 8.353310] [drm] CRT1: INTERNAL_KLDSCP_DAC1
>>>>> [ 8.358195] BUG: unable to handle kernel NULL pointer dereference at
>>>>> 0000000000000409
>>>>> [ 8.409733] [<ffffffffc02024da>] radeon_dp_getsinktype+0x1a/0x30
>>>>> [radeon]
>>>>> [ 8.416805] PGD 0
>>>>> [ 8.418841] Oops: 0000 [#1] SMP
>>>>> ...
>>>>>
>>>>> This patch prevents Kernel failures due to a connector not having a
>>>>> DDC interface by changing the code so that ddc_bus is always checked
>>>>> before use.
>>>>> The problem was first identified using the uBuntu MATE 14.04 LTS
>>>>> (3.16
>>>>> series kernels) but not dealt with at that time. On attempting to
>>>>> install uBuntu MATE 16.04 LTS (4.4 series kernels), it became clear
>>>>> that using various workarounds to allow the issue to be ignored were
>>>>> not viable so more effort was put in to sorting the issue
>>>>> resulting in
>>>>> this patch. See https://bugs.launchpad.net/bugs/1587885 for more
>>>>> details.
>>>>>
>>>>> Signed-off-by: Mark Fortescue <mark at thurning-instruments.co.uk>
>>>>> Tested-by: Mark Fortescue <mark at thurning-instruments.co.uk>
>>>>>
>>>>> ---
>>>>>
>>>>> Looks like Thunderbird may have made a mess of the patch when pasting
>>>>> the contents into the mail message - my alternate mail client (pine)
>>>>> also has strict line length handling and trashes non-MIME encoded
>>>>> patches.
>>>>>
>>>>> This may not be the correct approach to solving the issue but it is
>>>>> clean in that it ensures that ddc_bus is never used when NULL
>>>>> regardless of how the code ended up at the point of use.
>>>>>
>>>>> If it helps with back porting, I have patches for the uBuntu 14.04
>>>>> LTS
>>>>> [3.13 series], uBuntu MATE 14.04 LTS [3.16 series] and uBuntu 16.04
>>>>> LTS [4.4 series] kernels.
>>>>>
>>>>> Test Hardware:
>>>>> Commell LV-683 Mini-ITX with onboard AMD Dual-core G-T56N
>>>>> 4G Ram, 2x1TB Disk, HANNS-G HC194D 1280x1024 LCD (VGA).
>>>>> 4.8.0-rc5 with patch boots without error.
>>>>>
>>>>> drivers/gpu/drm/radeon/atombios_dp.c | 60
>>>>> ++++++++++++-------
>>>>> drivers/gpu/drm/radeon/radeon_connectors.c | 46 +++++++-------
>>>>> drivers/gpu/drm/radeon/radeon_dp_mst.c | 9 ++
>>>>> drivers/gpu/drm/radeon/radeon_i2c.c | 3
>>>>> 4 files changed, 73 insertions(+), 45 deletions(-)
>>>>>
>>>>> Patch:
>>>>> diff --git a/drivers/gpu/drm/radeon/atombios_dp.c
>>>>> b/drivers/gpu/drm/radeon/atombios_dp.c
>>>>> index cead089a..98b3c0e 100644
>>>>> --- a/drivers/gpu/drm/radeon/atombios_dp.c
>>>>> +++ b/drivers/gpu/drm/radeon/atombios_dp.c
>>>>> @@ -232,6 +232,9 @@ void radeon_dp_aux_init(struct radeon_connector
>>>>> *radeon_connector)
>>>>> struct radeon_device *rdev = dev->dev_private;
>>>>> int ret;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return;
>>>>> +
>>>>> radeon_connector->ddc_bus->rec.hpd = radeon_connector->hpd.hpd;
>>>>> radeon_connector->ddc_bus->aux.dev =
>>>>> radeon_connector->base.kdev;
>>>>> if (ASIC_IS_DCE5(rdev)) {
>>>>> @@ -364,6 +367,9 @@ u8 radeon_dp_getsinktype(struct radeon_connector
>>>>> *radeon_connector)
>>>>> struct drm_device *dev = radeon_connector->base.dev;
>>>>> struct radeon_device *rdev = dev->dev_private;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return 0;
>>>>> +
>>>>> return radeon_dp_encoder_service(rdev,
>>>>> ATOM_DP_ACTION_GET_SINK_TYPE, 0,
>>>>> radeon_connector->ddc_bus->rec.i2c_id, 0);
>>>>> }
>>>>> @@ -376,6 +382,9 @@ static void radeon_dp_probe_oui(struct
>>>>> radeon_connector *radeon_connector)
>>>>> if (!(dig_connector->dpcd[DP_DOWN_STREAM_PORT_COUNT] &
>>>>> DP_OUI_SUPPORT))
>>>>> return;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return;
>>>>> +
>>>>> if (drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux,
>>>>> DP_SINK_OUI, buf, 3) == 3)
>>>>> DRM_DEBUG_KMS("Sink OUI: %02hx%02hx%02hx\n",
>>>>> buf[0], buf[1], buf[2]);
>>>>> @@ -391,6 +400,9 @@ bool radeon_dp_getdpcd(struct radeon_connector
>>>>> *radeon_connector)
>>>>> u8 msg[DP_DPCD_SIZE];
>>>>> int ret, i;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return false;
>>>>> +
>>>>> for (i = 0; i < 7; i++) {
>>>>> ret = drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux,
>>>>> DP_DPCD_REV, msg,
>>>>> DP_DPCD_SIZE);
>>>>> @@ -428,24 +440,26 @@ int radeon_dp_get_panel_mode(struct drm_encoder
>>>>> *encoder,
>>>>>
>>>>> dig_connector = radeon_connector->con_priv;
>>>>>
>>>>> - if (dp_bridge != ENCODER_OBJECT_ID_NONE) {
>>>>> - /* DP bridge chips */
>>>>> - if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> - DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
>>>>> - if (tmp & 1)
>>>>> - panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
>>>>> - else if ((dp_bridge == ENCODER_OBJECT_ID_NUTMEG) ||
>>>>> - (dp_bridge == ENCODER_OBJECT_ID_TRAVIS))
>>>>> - panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
>>>>> - else
>>>>> - panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
>>>>> - }
>>>>> - } else if (connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_eDP) {
>>>>> - /* eDP */
>>>>> - if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> - DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
>>>>> - if (tmp & 1)
>>>>> - panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
>>>>> + if (radeon_connector->ddc_bus) {
>>>>> + if (dp_bridge != ENCODER_OBJECT_ID_NONE) {
>>>>> + /* DP bridge chips */
>>>>> + if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> + DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
>>>>> + if (tmp & 1)
>>>>> + panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
>>>>> + else if ((dp_bridge == ENCODER_OBJECT_ID_NUTMEG) ||
>>>>> + (dp_bridge == ENCODER_OBJECT_ID_TRAVIS))
>>>>> + panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
>>>>> + else
>>>>> + panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
>>>>> + }
>>>>> + } else if (connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_eDP) {
>>>>> + /* eDP */
>>>>> + if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> + DP_EDP_CONFIGURATION_CAP, &tmp) == 1) {
>>>>> + if (tmp & 1)
>>>>> + panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
>>>>> + }
>>>>> }
>>>>> }
>>>>>
>>>>> @@ -511,6 +525,9 @@ bool radeon_dp_needs_link_train(struct
>>>>> radeon_connector *radeon_connector)
>>>>> u8 link_status[DP_LINK_STATUS_SIZE];
>>>>> struct radeon_connector_atom_dig *dig =
>>>>> radeon_connector->con_priv;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return false;
>>>>> +
>>>>> if
>>>>> (drm_dp_dpcd_read_link_status(&radeon_connector->ddc_bus->aux,
>>>>> link_status)
>>>>> <= 0)
>>>>> return false;
>>>>> @@ -531,7 +548,7 @@ void radeon_dp_set_rx_power_state(struct
>>>>> drm_connector *connector,
>>>>> dig_connector = radeon_connector->con_priv;
>>>>>
>>>>> /* power up/down the sink */
>>>>> - if (dig_connector->dpcd[0] >= 0x11) {
>>>>> + if (radeon_connector->ddc_bus && dig_connector->dpcd[0] >=
>>>>> 0x11) {
>>>>> drm_dp_dpcd_writeb(&radeon_connector->ddc_bus->aux,
>>>>> DP_SET_POWER, power_state);
>>>>> usleep_range(1000, 2000);
>>>>> @@ -834,7 +851,8 @@ void radeon_dp_link_train(struct drm_encoder
>>>>> *encoder,
>>>>> else
>>>>> dp_info.enc_id |= ATOM_DP_CONFIG_LINK_A;
>>>>>
>>>>> - if (drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> DP_MAX_LANE_COUNT, &tmp)
>>>>> + if (radeon_connector->ddc_bus &&
>>>>> + drm_dp_dpcd_readb(&radeon_connector->ddc_bus->aux,
>>>>> DP_MAX_LANE_COUNT, &tmp)
>>>>> == 1) {
>>>>> if (ASIC_IS_DCE5(rdev) && (tmp & DP_TPS3_SUPPORTED))
>>>>> dp_info.tp3_supported = true;
>>>>> @@ -850,7 +868,7 @@ void radeon_dp_link_train(struct drm_encoder
>>>>> *encoder,
>>>>> dp_info.connector = connector;
>>>>> dp_info.dp_lane_count = dig_connector->dp_lane_count;
>>>>> dp_info.dp_clock = dig_connector->dp_clock;
>>>>> - dp_info.aux = &radeon_connector->ddc_bus->aux;
>>>>> + dp_info.aux = radeon_connector->ddc_bus ?
>>>>> &radeon_connector->ddc_bus->aux : 0;
>>>>>
>>>>> if (radeon_dp_link_train_init(&dp_info))
>>>>> goto done;
>>>>> diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c
>>>>> b/drivers/gpu/drm/radeon/radeon_connectors.c
>>>>> index b79f3b0..cec30c9 100644
>>>>> --- a/drivers/gpu/drm/radeon/radeon_connectors.c
>>>>> +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
>>>>> @@ -328,31 +328,32 @@ static void radeon_connector_get_edid(struct
>>>>> drm_connector *connector)
>>>>> if (radeon_connector->router.ddc_valid)
>>>>> radeon_router_select_ddc_port(radeon_connector);
>>>>>
>>>>> - if
>>>>> ((radeon_connector_encoder_get_dp_bridge_encoder_id(connector) !=
>>>>> - ENCODER_OBJECT_ID_NONE) &&
>>>>> - radeon_connector->ddc_bus->has_aux) {
>>>>> - radeon_connector->edid = drm_get_edid(connector,
>>>>> - &radeon_connector->ddc_bus->aux.ddc);
>>>>> - } else if ((connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_DisplayPort) ||
>>>>> - (connector->connector_type == DRM_MODE_CONNECTOR_eDP)) {
>>>>> - struct radeon_connector_atom_dig *dig =
>>>>> radeon_connector->con_priv;
>>>>> -
>>>>> - if ((dig->dp_sink_type == CONNECTOR_OBJECT_ID_DISPLAYPORT ||
>>>>> - dig->dp_sink_type == CONNECTOR_OBJECT_ID_eDP) &&
>>>>> - radeon_connector->ddc_bus->has_aux)
>>>>> - radeon_connector->edid =
>>>>> drm_get_edid(&radeon_connector->base,
>>>>> + if (radeon_connector->ddc_bus) {
>>>>> + if
>>>>> ((radeon_connector_encoder_get_dp_bridge_encoder_id(connector) !=
>>>>> + ENCODER_OBJECT_ID_NONE) &&
>>>>> + radeon_connector->ddc_bus->has_aux) {
>>>>> + radeon_connector->edid = drm_get_edid(connector,
>>>>> &radeon_connector->ddc_bus->aux.ddc);
>>>>> - else if (radeon_connector->ddc_bus)
>>>>> + } else if ((connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_DisplayPort) ||
>>>>> + (connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_eDP)) {
>>>>> + struct radeon_connector_atom_dig *dig =
>>>>> radeon_connector->con_priv;
>>>>> +
>>>>> + if ((dig->dp_sink_type ==
>>>>> CONNECTOR_OBJECT_ID_DISPLAYPORT ||
>>>>> + dig->dp_sink_type == CONNECTOR_OBJECT_ID_eDP) &&
>>>>> + radeon_connector->ddc_bus->has_aux)
>>>>> + radeon_connector->edid =
>>>>> drm_get_edid(&radeon_connector->base,
>>>>> + &radeon_connector->ddc_bus->aux.ddc);
>>>>> + else
>>>>> + radeon_connector->edid =
>>>>> drm_get_edid(&radeon_connector->base,
>>>>> + &radeon_connector->ddc_bus->adapter);
>>>>> + } else if (vga_switcheroo_handler_flags() &
>>>>> VGA_SWITCHEROO_CAN_SWITCH_DDC &&
>>>>> + connector->connector_type ==
>>>>> DRM_MODE_CONNECTOR_LVDS) {
>>>>> + radeon_connector->edid =
>>>>> drm_get_edid_switcheroo(&radeon_connector->base,
>>>>> + &radeon_connector->ddc_bus->adapter);
>>>>> + } else {
>>>>> radeon_connector->edid =
>>>>> drm_get_edid(&radeon_connector->base,
>>>>> &radeon_connector->ddc_bus->adapter);
>>>>> - } else if (vga_switcheroo_handler_flags() &
>>>>> VGA_SWITCHEROO_CAN_SWITCH_DDC &&
>>>>> - connector->connector_type == DRM_MODE_CONNECTOR_LVDS &&
>>>>> - radeon_connector->ddc_bus) {
>>>>> - radeon_connector->edid =
>>>>> drm_get_edid_switcheroo(&radeon_connector->base,
>>>>> - &radeon_connector->ddc_bus->adapter);
>>>>> - } else if (radeon_connector->ddc_bus) {
>>>>> - radeon_connector->edid =
>>>>> drm_get_edid(&radeon_connector->base,
>>>>> - &radeon_connector->ddc_bus->adapter);
>>>>> + }
>>>>> }
>>>>>
>>>>> if (!radeon_connector->edid) {
>>>>> @@ -1312,6 +1313,7 @@ radeon_dvi_detect(struct drm_connector
>>>>> *connector, bool force)
>>>>> continue;
>>>>> list_radeon_connector =
>>>>> to_radeon_connector(list_connector);
>>>>> if (list_radeon_connector->shared_ddc &&
>>>>> + radeon_connector->ddc_bus &&
>>>>> (list_radeon_connector->ddc_bus->rec.i2c_id ==
>>>>> radeon_connector->ddc_bus->rec.i2c_id)) {
>>>>> /* cases where both connectors are
>>>>> digital */
>>>>> diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c
>>>>> b/drivers/gpu/drm/radeon/radeon_dp_mst.c
>>>>> index de504ea..89e91f3 100644
>>>>> --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
>>>>> +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
>>>>> @@ -661,7 +661,7 @@ radeon_dp_mst_init(struct radeon_connector
>>>>> *radeon_connector)
>>>>> {
>>>>> struct drm_device *dev = radeon_connector->base.dev;
>>>>>
>>>>> - if (!radeon_connector->ddc_bus->has_aux)
>>>>> + if (!radeon_connector->ddc_bus ||
>>>>> !radeon_connector->ddc_bus->has_aux)
>>>>> return 0;
>>>>>
>>>>> radeon_connector->mst_mgr.cbs = &mst_cbs;
>>>>> @@ -688,6 +688,9 @@ radeon_dp_mst_probe(struct radeon_connector
>>>>> *radeon_connector)
>>>>> if (dig_connector->dpcd[DP_DPCD_REV] < 0x12)
>>>>> return 0;
>>>>>
>>>>> + if (!radeon_connector->ddc_bus ||
>>>>> !radeon_connector->ddc_bus->has_aux)
>>>>> + return 0;
>>>>> +
>>>>> ret = drm_dp_dpcd_read(&radeon_connector->ddc_bus->aux,
>>>>> DP_MSTM_CAP, msg,
>>>>> 1);
>>>>> if (ret) {
>>>>> @@ -711,7 +714,9 @@ radeon_dp_mst_check_status(struct
>>>>> radeon_connector
>>>>> *radeon_connector)
>>>>> struct radeon_connector_atom_dig *dig_connector =
>>>>> radeon_connector->con_priv;
>>>>> int retry;
>>>>>
>>>>> - if (dig_connector->is_mst) {
>>>>> + if (dig_connector->is_mst &&
>>>>> + radeon_connector->ddc_bus &&
>>>>> + radeon_connector->ddc_bus->has_aux) {
>>>>> u8 esi[16] = { 0 };
>>>>> int dret;
>>>>> int ret = 0;
>>>>> diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c
>>>>> b/drivers/gpu/drm/radeon/radeon_i2c.c
>>>>> index 9590bcd..c18f7ba 100644
>>>>> --- a/drivers/gpu/drm/radeon/radeon_i2c.c
>>>>> +++ b/drivers/gpu/drm/radeon/radeon_i2c.c
>>>>> @@ -63,6 +63,9 @@ bool radeon_ddc_probe(struct radeon_connector
>>>>> *radeon_connector, bool use_aux)
>>>>> if (radeon_connector->router.ddc_valid)
>>>>> radeon_router_select_ddc_port(radeon_connector);
>>>>>
>>>>> + if (!radeon_connector->ddc_bus)
>>>>> + return false;
>>>>> +
>>>>> if (use_aux) {
>>>>> ret = i2c_transfer(&radeon_connector->ddc_bus->aux.ddc,
>>>>> msgs, 2);
>>>>> } else {
>>>>> _______________________________________________
>>>>> dri-devel mailing list
>>>>> dri-devel at lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>
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