Messages in this thread | | | Subject | Re: [PATCH] drm/vc4: Fix HDMI mode validation | From | Stefan Wahren <> | Date | Thu, 26 Mar 2020 18:19:41 +0100 |
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Am 26.03.20 um 13:20 schrieb Nicolas Saenz Julienne: > Current mode validation impedes setting up some video modes which should > be supported otherwise. Namely 1920x1200@60Hz. > > Fix this by lowering the minimum HDMI state machine clock to pixel clock > ratio allowed. > > Fixes: 32e823c63e90 ("drm/vc4: Reject HDMI modes with too high of clocks") > Reported-by: Stefan Wahren <stefan.wahren@i2se.com> > Suggested-by: Dave Stevenson <dave.stevenson@raspberrypi.com> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > --- > drivers/gpu/drm/vc4/vc4_hdmi.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c > index cea18dc15f77..340719238753 100644 > --- a/drivers/gpu/drm/vc4/vc4_hdmi.c > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c > @@ -681,11 +681,23 @@ 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. > + /* > + * As stated in RPi's vc4 firmware "HDMI state machine (HSM) clock must > + * be faster than pixel clock, infinitesimally faster, tested in > + * simulation. Otherwise, exact value is unimportant for HDMI > + * operation." This conflicts with bcm2835's vc4 documentation, which > + * states HSM's clock has to be at least 108% of the pixel clock. > + * > + * Real life tests reveal that vc4's firmware statement holds up, and > + * users are able to use pixel clocks closer to HSM's, namely for > + * 1920x1200@60Hz. So it was decided to have leave a 1% margin between > + * both clocks. Which, for RPi0-3 implies a maximum pixel clock of
s/RPi0-3/bcm2835/ ?
Beside this nit:
Tested-by: Stefan Wahren <stefan.wahre@i2se.com>
Thanks
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