drm/vc4: Reject HDMI modes with too high of clocks.

Peter Robinson reported issues on Fedora with 4k monitors not having
their modes filtered down to 1920x1080 on Raspberry Pi.

v2: Fix vc5 typo in place of vc4.

Cc: Peter Robinson <pbrobinson@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20170920225935.14566-1-eric@anholt.net
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 9a9a6b4acccfdd323e8a956f45fc8b6ffef7b348..ab3bcbe0bb93f34c09966f6989e9f45eb46bc90e 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -693,7 +693,22 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
        }
 }
 
+static enum drm_mode_status
+vc4_hdmi_encoder_mode_valid(struct drm_encoder *crtc,
+                           const struct drm_display_mode *mode)
+{
+       /* HSM clock must be 108% of the pixel clock.  Additionally,
+        * the AXI clock needs to be at least 25% of pixel clock, but
+        * HSM ends up being the limiting factor.
+        */
+       if (mode->clock > HSM_CLOCK_FREQ / (1000 * 108 / 100))
+               return MODE_CLOCK_HIGH;
+
+       return MODE_OK;
+}
+
 static const struct drm_encoder_helper_funcs vc4_hdmi_encoder_helper_funcs = {
+       .mode_valid = vc4_hdmi_encoder_mode_valid,
        .disable = vc4_hdmi_encoder_disable,
        .enable = vc4_hdmi_encoder_enable,
 };