Russell,
On Wed, Jun 17, 2015 at 4:30 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Wed, Jun 17, 2015 at 04:14:07PM -0700, Doug Anderson wrote:
>> If you plug in a DVI monitor to your HDMI port, you need to filter out
>> clocks > 165MHz. That's because 165MHz is the maximum clock rate that
>> we can run single-link DVI at.
>>
>> If you want to run high resolutions to DVI, you'd need some type of an
>> active adapter that pretended that it was HDMI, interpreted the
>> signal, and produced a new dual link DVI signal at a lower clock rate.
>>
>> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
>> ---
>> Note: this patch was tested against a 3.14 kernel with backports. It
>> was only compile tested against linuxnext, but the code is
>> sufficiently similar that I'm convinced it will work there.
>
> Really? I have to wonder what your testing was...
>
> hdmi->vic = drm_match_cea_mode(mode);
>
> if (!hdmi->vic) {
> dev_dbg(hdmi->dev, "Non-CEA mode used in HDMI\n");
> hdmi->hdmi_data.video_mode.mdvi = true;
> } else {
> dev_dbg(hdmi->dev, "CEA mode used vic=%d\n", hdmi->vic);
> hdmi->hdmi_data.video_mode.mdvi = false;
> }
>
> mdvi indicates whether the _currently set mode_ is a CEA mode or not (imho,
> it's mis-named). It doesn't indicate whether we have a HDMI display device
> or a DVI display device connected, which seems to be what you want to use
> it for below.
>
> To sort that, what you need to do is detect a HDMI display device using
> drm_detect_hdmi_monitor() on the EDID received from the device before
> parsing the modes, and save that value in a dw_hdmi struct member, and
> I'd suggest that it's a top-level struct member, not buried in 'hdmi_data'
> or 'video_mode'.
OK, so clearly my patch won't work against mainline. I guess it's a
good thing that I pointed out that it was only tested locally (would
have been better to test against mainline, but I don't think that's so
easy since there are several unlanded patches in mainline for
Rockchip).
As pointed out by others at <http://crosreview.com/278255>, locally
our kernel has a slightly older version of
<https://lkml.org/lkml/2015/2/28/291>, which would change mdvi to be
as needed.
...so I guess my change is blocked on someone reviewing/landing that
series. If that series is rejected (or is changed sufficiently so
that mdvi no longer is set via drm_detect_hdmi_monitor() then my patch
will need to be re-spun.
-Doug
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