diff options
| author | Hans Verkuil <hverkuil@xs4all.nl> | 2017-12-15 16:21:50 +0100 |
|---|---|---|
| committer | Maxime Ripard <maxime.ripard@free-electrons.com> | 2017-12-15 22:24:03 +0100 |
| commit | caea4f384858ee7861367920df36995e7acfe160 (patch) | |
| tree | 65b7874cc1664af83df979e728ea7658dc9c8812 /drivers/gpu/drm | |
| parent | bd36d3bab2e3d08f80766c86487090dbceed4651 (diff) | |
drm/sun4i: validate modes for HDMI
When I connected my cubieboard running 4.15-rc1 to my 4k display I got no
picture. Some digging found that there is no check against the upper
pixelclock limit of the HDMI output, so X selects a 4kp60 format at 594
MHz, which obviously won't work.
The patch below adds a check for the upper bound of what this hardware can
do, and it checks if the requested tmds clock can be obtained.
It also allows for the +/- 0.5% pixel clock variation that the HDMI spec permits.
That code is based on commit 22d0be2a557e ("drm: arcpgu: Allow some clock
deviation in crtc->mode_valid() callback") from Jose Abreu for drm/arc.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Thanks-to: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/162854cb-c7bd-d9ce-9fa0-9a6cd89c621b@xs4all.nl
Diffstat (limited to 'drivers/gpu/drm')
| -rw-r--r-- | drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c index dda904ec0534..c12f9bd12904 100644 --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c @@ -208,8 +208,27 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector) return ret; } +static int sun4i_hdmi_mode_valid(struct drm_connector *connector, + struct drm_display_mode *mode) +{ + struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector); + long rate = mode->clock * 1000; + long diff = rate / 200; /* +-0.5% allowed by HDMI spec */ + long rounded_rate; + + /* 165 MHz is the typical max pixelclock frequency for HDMI <= 1.2 */ + if (rate > 165000000) + return MODE_CLOCK_HIGH; + rounded_rate = clk_round_rate(hdmi->tmds_clk, rate); + if (max(rounded_rate, rate) - min(rounded_rate, rate) < diff && + rounded_rate > 0) + return MODE_OK; + return MODE_NOCLOCK; +} + static const struct drm_connector_helper_funcs sun4i_hdmi_connector_helper_funcs = { .get_modes = sun4i_hdmi_get_modes, + .mode_valid = sun4i_hdmi_mode_valid, }; static enum drm_connector_status |