On 4/26/2022 1:26 PM, Doug Anderson wrote:
> Hi,
>
> On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar
> <[email protected]> wrote:
>>
>> Missed one more comment.
>>
>> On 4/26/2022 12:16 PM, Abhinav Kumar wrote:
>>> Hi Doug
>>>
>>> One minor comment below.
>>>
>>> But otherwise, looking at this change this should work for us acc to me.
>>>
>>> We will test this out with our equipment and then provide R-b.
>>>
>>> Thanks
>>>
>>> Abhinav
>>> On 4/26/2022 11:46 AM, Douglas Anderson wrote:
>>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says
>>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe
>>>> mode.
>>>>
>>>> A DP compliance test expected us to utilize the above fact when all
>>>> modes it presented to the DP source were not achievable. It presented
>>>> only modes that would be achievable with more lanes and/or higher
>>>> speeds than we had available and expected that when we couldn't do
>>>> that then we'd fall back to 640x480 even though it didn't advertise
>>>> this size.
>>>>
>>>> In order to pass the compliance test (and also support any users who
>>>> might fall into a similar situation with their display), we need to
>>>> add 640x480 into the list of modes. However, we don't want to add
>>>> 640x480 all the time. Despite the fact that the DP spec says all sinks
>>>> _shall support_ 640x480, they're not guaranteed to support it
>>>> _well_. Continuing to read the spec you can see that the display is
>>>> not required to really treat 640x480 equal to all the other modes. It
>>>> doesn't need to scale or anything--just display the pixels somehow for
>>>> failsafe purposes. It should also be noted that it's not hard to find
>>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at
>>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port
>>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI
>>>> display via a DP to HDMI adapter and that screen definitely doesn't
>>>> support 640x480.
>>>>
>>>> As a compromise solution, let's only add the 640x480 mode if:
>>>> * We're on DP.
>>>> * All other modes have been pruned.
>>>>
>>>> This acknowledges that 640x480 might not be the best mode to use but,
>>>> since sinks are _supposed_ to support it, we will at least fall back
>>>> to it if there's nothing else.
>>>>
>>>> Note that we _don't_ add higher resolution modes like 1024x768 in this
>>>> case. We only add those modes for a failed EDID read where we have no
>>>> idea what's going on. In the case where we've pruned all modes then
>>>> instead we only want 640x480 which is the only defined "Fail Safe"
>>>> resolution.
>>>>
>>>> This patch originated in response to Kuogee Hsieh's patch [1].
>>>>
>>>> [1]
>>>> https://lore.kernel.org/r/[email protected]
>>>>
>>>>
>>>> Signed-off-by: Douglas Anderson <[email protected]>
>>>> ---
>>>>
>>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++-----
>>>> 1 file changed, 21 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c
>>>> b/drivers/gpu/drm/drm_probe_helper.c
>>>> index 819225629010..90cd46cbfec1 100644
>>>> --- a/drivers/gpu/drm/drm_probe_helper.c
>>>> +++ b/drivers/gpu/drm/drm_probe_helper.c
>>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct
>>>> drm_connector *connector,
>>>> const struct drm_connector_helper_funcs *connector_funcs =
>>>> connector->helper_private;
>>>> int count = 0, ret;
>>>> - bool verbose_prune = true;
>>>> enum drm_connector_status old_status;
>>>> struct drm_modeset_acquire_ctx ctx;
>>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct
>>>> drm_connector *connector,
>>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
>>>> connector->base.id, connector->name);
>>>> drm_connector_update_edid_property(connector, NULL);
>>>> - verbose_prune = false;
>>>> - goto prune;
>>>> + drm_mode_prune_invalid(dev, &connector->modes, false);
>>>> + goto exit;
>>>> }
>>>> count = (*connector_funcs->get_modes)(connector);
>>>> @@ -580,9 +579,26 @@ int
>>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>>>> }
>>>> }
>>>> -prune:
>>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
>>>> + drm_mode_prune_invalid(dev, &connector->modes, true);
>>>> + /*
>>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says
>>>> that
>>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe
>>>> + * mode. If all modes were pruned, perhaps because they need more
>>>> + * lanes or a higher pixel clock than available, at least try to add
>>>> + * in 640x480.
>>>> + */
>>>> + if (list_empty(&connector->modes) &&
>>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
>>>> + count = drm_add_modes_noedid(connector, 640, 480);
>>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY,
>>>> &ctx)) {
>>>> + drm_modeset_backoff(&ctx);
>>>> + goto retry;
>>>
>>> Do we need another retry here? This will again repeat everything from
>>> get_modes().
>>> The fact that we are hitting this code is because we have already tried
>>> that and this is already a second-pass. So I think another retry isnt
>>> needed?
>>
>> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1.
>>
>> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of
>> adding all modes <= 1024x768 will kick in.
>>
>> Now, in that list, we will still need to pick/mark 640x480 as the
>> preferred mode.
>>
>> We still need IGT for that.
>
> Are you sure you don't have those backwards? It seems like 4.2.2.6 is
> the test case dealing with corrupt EDID and that's the one that will
> still be broken, no? ...and corrupt EDID is still the case where we
> have 0 modes.
Yes indeed, sorry, I did have the numbers backwards.
4.2.2.6 will still be broken.
>
> In any case, let's see what people think about:
>
> https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid
Yes sure. If it gets accepted, it will save us some IGT work.
>
> I've marked that one as RFC just because it seems like a bigger change
> to existing behavior, though it still seems correct to me.
>
> NOTE: reading 4.2.2.6 more closely, it actually looks as if we're
> actually supposed to be able to try various video modes one at a time
> until we find one that works (or land on 640x480). Seems as if we're
> supposed to be able to try the higher resolutions one at a time and we
> can tell whether the sink "accepted" it by seeing if SINK_STATUS goes
> to 1? I have no idea how that works with all the Linux APIs, though.
>
hmmm .... our equipment throws a warning if we dont sent 640x480. So
perhaps just go with the "or land on 640x480" option.
0006.392.232: [WARNING] Source DUT failed to transmit a video stream
using fail-safe mode
0006.392.491: Received 1344 Htotal differs from fail-safe 800
0006.392.621: Received 1024 Hactive differs from fail-safe 640
0006.392.750: Received 296 Hstart differs from fail-safe 144
0006.392.868: Received 136 Hsync width differs from fail-safe 96
0006.392.975: Received 806 Vtotal differs from fail-safe 525
0006.393.099: Received 768 Vactive differs from fail-safe 480
0006.393.229: Received 6 Vsync width differs from fail-safe 2
> -Doug
Hi,
On Tue, Apr 26, 2022 at 2:11 PM Abhinav Kumar <[email protected]> wrote:
>
>
>
> On 4/26/2022 1:26 PM, Doug Anderson wrote:
> > Hi,
> >
> > On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar
> > <[email protected]> wrote:
> >>
> >> Missed one more comment.
> >>
> >> On 4/26/2022 12:16 PM, Abhinav Kumar wrote:
> >>> Hi Doug
> >>>
> >>> One minor comment below.
> >>>
> >>> But otherwise, looking at this change this should work for us acc to me.
> >>>
> >>> We will test this out with our equipment and then provide R-b.
> >>>
> >>> Thanks
> >>>
> >>> Abhinav
> >>> On 4/26/2022 11:46 AM, Douglas Anderson wrote:
> >>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says
> >>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe
> >>>> mode.
> >>>>
> >>>> A DP compliance test expected us to utilize the above fact when all
> >>>> modes it presented to the DP source were not achievable. It presented
> >>>> only modes that would be achievable with more lanes and/or higher
> >>>> speeds than we had available and expected that when we couldn't do
> >>>> that then we'd fall back to 640x480 even though it didn't advertise
> >>>> this size.
> >>>>
> >>>> In order to pass the compliance test (and also support any users who
> >>>> might fall into a similar situation with their display), we need to
> >>>> add 640x480 into the list of modes. However, we don't want to add
> >>>> 640x480 all the time. Despite the fact that the DP spec says all sinks
> >>>> _shall support_ 640x480, they're not guaranteed to support it
> >>>> _well_. Continuing to read the spec you can see that the display is
> >>>> not required to really treat 640x480 equal to all the other modes. It
> >>>> doesn't need to scale or anything--just display the pixels somehow for
> >>>> failsafe purposes. It should also be noted that it's not hard to find
> >>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at
> >>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port
> >>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI
> >>>> display via a DP to HDMI adapter and that screen definitely doesn't
> >>>> support 640x480.
> >>>>
> >>>> As a compromise solution, let's only add the 640x480 mode if:
> >>>> * We're on DP.
> >>>> * All other modes have been pruned.
> >>>>
> >>>> This acknowledges that 640x480 might not be the best mode to use but,
> >>>> since sinks are _supposed_ to support it, we will at least fall back
> >>>> to it if there's nothing else.
> >>>>
> >>>> Note that we _don't_ add higher resolution modes like 1024x768 in this
> >>>> case. We only add those modes for a failed EDID read where we have no
> >>>> idea what's going on. In the case where we've pruned all modes then
> >>>> instead we only want 640x480 which is the only defined "Fail Safe"
> >>>> resolution.
> >>>>
> >>>> This patch originated in response to Kuogee Hsieh's patch [1].
> >>>>
> >>>> [1]
> >>>> https://lore.kernel.org/r/[email protected]
> >>>>
> >>>>
> >>>> Signed-off-by: Douglas Anderson <[email protected]>
> >>>> ---
> >>>>
> >>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++-----
> >>>> 1 file changed, 21 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c
> >>>> b/drivers/gpu/drm/drm_probe_helper.c
> >>>> index 819225629010..90cd46cbfec1 100644
> >>>> --- a/drivers/gpu/drm/drm_probe_helper.c
> >>>> +++ b/drivers/gpu/drm/drm_probe_helper.c
> >>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct
> >>>> drm_connector *connector,
> >>>> const struct drm_connector_helper_funcs *connector_funcs =
> >>>> connector->helper_private;
> >>>> int count = 0, ret;
> >>>> - bool verbose_prune = true;
> >>>> enum drm_connector_status old_status;
> >>>> struct drm_modeset_acquire_ctx ctx;
> >>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct
> >>>> drm_connector *connector,
> >>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
> >>>> connector->base.id, connector->name);
> >>>> drm_connector_update_edid_property(connector, NULL);
> >>>> - verbose_prune = false;
> >>>> - goto prune;
> >>>> + drm_mode_prune_invalid(dev, &connector->modes, false);
> >>>> + goto exit;
> >>>> }
> >>>> count = (*connector_funcs->get_modes)(connector);
> >>>> @@ -580,9 +579,26 @@ int
> >>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector,
> >>>> }
> >>>> }
> >>>> -prune:
> >>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
> >>>> + drm_mode_prune_invalid(dev, &connector->modes, true);
> >>>> + /*
> >>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says
> >>>> that
> >>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe
> >>>> + * mode. If all modes were pruned, perhaps because they need more
> >>>> + * lanes or a higher pixel clock than available, at least try to add
> >>>> + * in 640x480.
> >>>> + */
> >>>> + if (list_empty(&connector->modes) &&
> >>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
> >>>> + count = drm_add_modes_noedid(connector, 640, 480);
> >>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY,
> >>>> &ctx)) {
> >>>> + drm_modeset_backoff(&ctx);
> >>>> + goto retry;
> >>>
> >>> Do we need another retry here? This will again repeat everything from
> >>> get_modes().
> >>> The fact that we are hitting this code is because we have already tried
> >>> that and this is already a second-pass. So I think another retry isnt
> >>> needed?
> >>
> >> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1.
> >>
> >> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of
> >> adding all modes <= 1024x768 will kick in.
> >>
> >> Now, in that list, we will still need to pick/mark 640x480 as the
> >> preferred mode.
> >>
> >> We still need IGT for that.
> >
> > Are you sure you don't have those backwards? It seems like 4.2.2.6 is
> > the test case dealing with corrupt EDID and that's the one that will
> > still be broken, no? ...and corrupt EDID is still the case where we
> > have 0 modes.
>
> Yes indeed, sorry, I did have the numbers backwards.
> 4.2.2.6 will still be broken.
>
> >
> > In any case, let's see what people think about:
> >
> > https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid
>
> Yes sure. If it gets accepted, it will save us some IGT work.
>
> >
> > I've marked that one as RFC just because it seems like a bigger change
> > to existing behavior, though it still seems correct to me.
> >
> > NOTE: reading 4.2.2.6 more closely, it actually looks as if we're
> > actually supposed to be able to try various video modes one at a time
> > until we find one that works (or land on 640x480). Seems as if we're
> > supposed to be able to try the higher resolutions one at a time and we
> > can tell whether the sink "accepted" it by seeing if SINK_STATUS goes
> > to 1? I have no idea how that works with all the Linux APIs, though.
> >
>
> hmmm .... our equipment throws a warning if we dont sent 640x480. So
> perhaps just go with the "or land on 640x480" option.
>
> 0006.392.232: [WARNING] Source DUT failed to transmit a video stream
> using fail-safe mode
> 0006.392.491: Received 1344 Htotal differs from fail-safe 800
> 0006.392.621: Received 1024 Hactive differs from fail-safe 640
> 0006.392.750: Received 296 Hstart differs from fail-safe 144
> 0006.392.868: Received 136 Hsync width differs from fail-safe 96
> 0006.392.975: Received 806 Vtotal differs from fail-safe 525
> 0006.393.099: Received 768 Vactive differs from fail-safe 480
> 0006.393.229: Received 6 Vsync width differs from fail-safe 2
Do you actually have code to implement the checking of SINK_STATUS?
I'm not aware of how that would work in Linux, which is why just
defaulting to 640x480 seems like a reasonable thing to do for now. The
test case actually says that you're allowed to try clock rates one at
a time (polling SINK_STATUS in DPCT) as long as you don't spend more
than 5 seconds on each clock rate. According to the test case if you
never saw SINK_STATUS in DPCT go to 1 then you should end at 640x480.
Tested-by: Kuogee Hsieh <[email protected]>
On 4/26/2022 2:17 PM, Doug Anderson wrote:
> Hi,
>
> On Tue, Apr 26, 2022 at 2:11 PM Abhinav Kumar <[email protected]> wrote:
>>
>>
>> On 4/26/2022 1:26 PM, Doug Anderson wrote:
>>> Hi,
>>>
>>> On Tue, Apr 26, 2022 at 12:20 PM Abhinav Kumar
>>> <[email protected]> wrote:
>>>> Missed one more comment.
>>>>
>>>> On 4/26/2022 12:16 PM, Abhinav Kumar wrote:
>>>>> Hi Doug
>>>>>
>>>>> One minor comment below.
>>>>>
>>>>> But otherwise, looking at this change this should work for us acc to me.
>>>>>
>>>>> We will test this out with our equipment and then provide R-b.
>>>>>
>>>>> Thanks
>>>>>
>>>>> Abhinav
>>>>> On 4/26/2022 11:46 AM, Douglas Anderson wrote:
>>>>>> As per Displayport spec section 5.2.1.2 ("Video Timing Format") says
>>>>>> that all detachable sinks shall support 640x480 @60Hz as a fail safe
>>>>>> mode.
>>>>>>
>>>>>> A DP compliance test expected us to utilize the above fact when all
>>>>>> modes it presented to the DP source were not achievable. It presented
>>>>>> only modes that would be achievable with more lanes and/or higher
>>>>>> speeds than we had available and expected that when we couldn't do
>>>>>> that then we'd fall back to 640x480 even though it didn't advertise
>>>>>> this size.
>>>>>>
>>>>>> In order to pass the compliance test (and also support any users who
>>>>>> might fall into a similar situation with their display), we need to
>>>>>> add 640x480 into the list of modes. However, we don't want to add
>>>>>> 640x480 all the time. Despite the fact that the DP spec says all sinks
>>>>>> _shall support_ 640x480, they're not guaranteed to support it
>>>>>> _well_. Continuing to read the spec you can see that the display is
>>>>>> not required to really treat 640x480 equal to all the other modes. It
>>>>>> doesn't need to scale or anything--just display the pixels somehow for
>>>>>> failsafe purposes. It should also be noted that it's not hard to find
>>>>>> a display hooked up via DisplayPort that _doesn't_ support 640x480 at
>>>>>> all. The HP ZR30w screen I'm sitting in front of has a native DP port
>>>>>> and doesn't work at 640x480. I also plugged in a tiny 800x480 HDMI
>>>>>> display via a DP to HDMI adapter and that screen definitely doesn't
>>>>>> support 640x480.
>>>>>>
>>>>>> As a compromise solution, let's only add the 640x480 mode if:
>>>>>> * We're on DP.
>>>>>> * All other modes have been pruned.
>>>>>>
>>>>>> This acknowledges that 640x480 might not be the best mode to use but,
>>>>>> since sinks are _supposed_ to support it, we will at least fall back
>>>>>> to it if there's nothing else.
>>>>>>
>>>>>> Note that we _don't_ add higher resolution modes like 1024x768 in this
>>>>>> case. We only add those modes for a failed EDID read where we have no
>>>>>> idea what's going on. In the case where we've pruned all modes then
>>>>>> instead we only want 640x480 which is the only defined "Fail Safe"
>>>>>> resolution.
>>>>>>
>>>>>> This patch originated in response to Kuogee Hsieh's patch [1].
>>>>>>
>>>>>> [1]
>>>>>> https://lore.kernel.org/r/[email protected]
>>>>>>
>>>>>>
>>>>>> Signed-off-by: Douglas Anderson <[email protected]>
>>>>>> ---
>>>>>>
>>>>>> drivers/gpu/drm/drm_probe_helper.c | 26 +++++++++++++++++++++-----
>>>>>> 1 file changed, 21 insertions(+), 5 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c
>>>>>> b/drivers/gpu/drm/drm_probe_helper.c
>>>>>> index 819225629010..90cd46cbfec1 100644
>>>>>> --- a/drivers/gpu/drm/drm_probe_helper.c
>>>>>> +++ b/drivers/gpu/drm/drm_probe_helper.c
>>>>>> @@ -476,7 +476,6 @@ int drm_helper_probe_single_connector_modes(struct
>>>>>> drm_connector *connector,
>>>>>> const struct drm_connector_helper_funcs *connector_funcs =
>>>>>> connector->helper_private;
>>>>>> int count = 0, ret;
>>>>>> - bool verbose_prune = true;
>>>>>> enum drm_connector_status old_status;
>>>>>> struct drm_modeset_acquire_ctx ctx;
>>>>>> @@ -556,8 +555,8 @@ int drm_helper_probe_single_connector_modes(struct
>>>>>> drm_connector *connector,
>>>>>> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
>>>>>> connector->base.id, connector->name);
>>>>>> drm_connector_update_edid_property(connector, NULL);
>>>>>> - verbose_prune = false;
>>>>>> - goto prune;
>>>>>> + drm_mode_prune_invalid(dev, &connector->modes, false);
>>>>>> + goto exit;
>>>>>> }
>>>>>> count = (*connector_funcs->get_modes)(connector);
>>>>>> @@ -580,9 +579,26 @@ int
>>>>>> drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>>>>>> }
>>>>>> }
>>>>>> -prune:
>>>>>> - drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
>>>>>> + drm_mode_prune_invalid(dev, &connector->modes, true);
>>>>>> + /*
>>>>>> + * Displayport spec section 5.2.1.2 ("Video Timing Format") says
>>>>>> that
>>>>>> + * all detachable sinks shall support 640x480 @60Hz as a fail safe
>>>>>> + * mode. If all modes were pruned, perhaps because they need more
>>>>>> + * lanes or a higher pixel clock than available, at least try to add
>>>>>> + * in 640x480.
>>>>>> + */
>>>>>> + if (list_empty(&connector->modes) &&
>>>>>> + connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
>>>>>> + count = drm_add_modes_noedid(connector, 640, 480);
>>>>>> + if (_drm_helper_update_and_validate(connector, maxX, maxY,
>>>>>> &ctx)) {
>>>>>> + drm_modeset_backoff(&ctx);
>>>>>> + goto retry;
>>>>> Do we need another retry here? This will again repeat everything from
>>>>> get_modes().
>>>>> The fact that we are hitting this code is because we have already tried
>>>>> that and this is already a second-pass. So I think another retry isnt
>>>>> needed?
>>>> This will help cover the case of 4.2.2.6 but not fix 4.2.2.1.
>>>>
>>>> For 4.2.2.1, we will have 0 modes and so the original DRM fwk code of
>>>> adding all modes <= 1024x768 will kick in.
>>>>
>>>> Now, in that list, we will still need to pick/mark 640x480 as the
>>>> preferred mode.
>>>>
>>>> We still need IGT for that.
>>> Are you sure you don't have those backwards? It seems like 4.2.2.6 is
>>> the test case dealing with corrupt EDID and that's the one that will
>>> still be broken, no? ...and corrupt EDID is still the case where we
>>> have 0 modes.
>> Yes indeed, sorry, I did have the numbers backwards.
>> 4.2.2.6 will still be broken.
>>
>>> In any case, let's see what people think about:
>>>
>>> https://lore.kernel.org/r/20220426132121.RFC.1.I31ec454f8d4ffce51a7708a8092f8a6f9c929092@changeid
>> Yes sure. If it gets accepted, it will save us some IGT work.
>>
>>> I've marked that one as RFC just because it seems like a bigger change
>>> to existing behavior, though it still seems correct to me.
>>>
>>> NOTE: reading 4.2.2.6 more closely, it actually looks as if we're
>>> actually supposed to be able to try various video modes one at a time
>>> until we find one that works (or land on 640x480). Seems as if we're
>>> supposed to be able to try the higher resolutions one at a time and we
>>> can tell whether the sink "accepted" it by seeing if SINK_STATUS goes
>>> to 1? I have no idea how that works with all the Linux APIs, though.
>>>
>> hmmm .... our equipment throws a warning if we dont sent 640x480. So
>> perhaps just go with the "or land on 640x480" option.
>>
>> 0006.392.232: [WARNING] Source DUT failed to transmit a video stream
>> using fail-safe mode
>> 0006.392.491: Received 1344 Htotal differs from fail-safe 800
>> 0006.392.621: Received 1024 Hactive differs from fail-safe 640
>> 0006.392.750: Received 296 Hstart differs from fail-safe 144
>> 0006.392.868: Received 136 Hsync width differs from fail-safe 96
>> 0006.392.975: Received 806 Vtotal differs from fail-safe 525
>> 0006.393.099: Received 768 Vactive differs from fail-safe 480
>> 0006.393.229: Received 6 Vsync width differs from fail-safe 2
> Do you actually have code to implement the checking of SINK_STATUS?
> I'm not aware of how that would work in Linux, which is why just
> defaulting to 640x480 seems like a reasonable thing to do for now. The
> test case actually says that you're allowed to try clock rates one at
> a time (polling SINK_STATUS in DPCT) as long as you don't spend more
> than 5 seconds on each clock rate. According to the test case if you
> never saw SINK_STATUS in DPCT go to 1 then you should end at 640x480.