RE: [PATCH 001/001] drivers/gpu/radeon: NULL pointer deference workaround

[Deucher, Alexander]

> -----Original Message-----
> From: Koenig, Christian
> Sent: Friday, September 09, 2016 4:16 AM
> To: Mark Fortescue; Koenig, Christian; David Airlie
> Cc: Deucher, Alexander; linux-kernel@xxxxxxxxxxxxxxx; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 001/001] drivers/gpu/radeon: NULL pointer deference
> workaround
> 
> >> 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 :).

Generally these sorts of setups are supported by exposing an LVDS or eDP connector rather than a regular DP.  In the case of LVDS and eDP, we have code to fallback to a hardcoded EDID in the vbios if DDC is not available.  I'll take a closer look when I'm back.

Alex

> 
> Cheers,
> Christian.
> 
> Am 08.09.2016 um 13:18 schrieb Mark Fortescue:
> > On 08/09/16 11:25, Christian KÃnig 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 KÃnig 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@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> >>>>> Tested-by: Mark Fortescue <mark@xxxxxxxxxxxxxxxxxxxxxxxxxx>
> >>>>>
> >>>>> ---
> >>>>>
> >>>>> 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@xxxxxxxxxxxxxxxxxxxxx
> >>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >>>>
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>