Hi, On 10/01/2024 00:07, Christian Hewitt wrote:
Playing 4K media with 59.94 fractional rate (typically VP9) causes the screen to lose sync with the following error reported in the system log: [ 89.610280] Fatal Error, invalid HDMI vclk freq 593406 Modetest shows the following: 3840x2160 59.94 3840 4016 4104 4400 2160 2168 2178 2250 593407 flags: xxxx, xxxx, drm calculated value -------------------------------------^ Change the fractional rate calculation to stop DIV_ROUND_CLOSEST rounding down which results in vclk freq failing to match correctly.
Thanks for the patch, it may need to closely look what's would be the consequence here, since /1000)*1000 would reduce comparison to less digits, but why ? A good thing would be to find the offending commit of when this broke, or redo the entire math because it looks super fishy a few years later... What puzzles me is that the same calculation is done on both side: - meson_vclk_vic_supported_freq() called from meson_encoder_hdmi_mode_valid() - meson_vclk_setup() called from meson_encoder_hdmi_set_vclk() and meson_encoder_hdmi_atomic_enable() so when a mode freq is selected from meson_encoder_hdmi_mode_valid(), it should match the mode freq in meson_vclk_setup(), but no. So why reducing precision makes this work ??? Neil
Fixes: e5fab2ec9ca4 ("drm/meson: vclk: add support for YUV420 setup") Signed-off-by: Christian Hewitt <christianshewitt@xxxxxxxxx> --- I'm unable to give a better mathematical description of the fix as I can barely read code. The change was inspired by [0] which I chanced upon while looking at how other dw-hdmi drivers handle fractional rates. [0] https://github.com/torvalds/linux/commit/4f510aa10468954b1da4e94689c38ac6ea8d3627 drivers/gpu/drm/meson/meson_vclk.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/meson/meson_vclk.c b/drivers/gpu/drm/meson/meson_vclk.c index 2a82119eb58e..2a942dc6a6dc 100644 --- a/drivers/gpu/drm/meson/meson_vclk.c +++ b/drivers/gpu/drm/meson/meson_vclk.c @@ -790,13 +790,13 @@ meson_vclk_vic_supported_freq(struct meson_drm *priv, unsigned int phy_freq, FREQ_1000_1001(params[i].pixel_freq)); DRM_DEBUG_DRIVER("i = %d phy_freq = %d alt = %d\n", i, params[i].phy_freq, - FREQ_1000_1001(params[i].phy_freq/10)*10); + FREQ_1000_1001(params[i].phy_freq/1000)*1000); /* Match strict frequency */ if (phy_freq == params[i].phy_freq && vclk_freq == params[i].vclk_freq) return MODE_OK; /* Match 1000/1001 variant */ - if (phy_freq == (FREQ_1000_1001(params[i].phy_freq/10)*10) && + if (phy_freq == (FREQ_1000_1001(params[i].phy_freq/1000)*1000) && vclk_freq == FREQ_1000_1001(params[i].vclk_freq)) return MODE_OK; } @@ -1070,7 +1070,7 @@ void meson_vclk_setup(struct meson_drm *priv, unsigned int target,for (freq = 0 ; params[freq].pixel_freq ; ++freq) {if ((phy_freq == params[freq].phy_freq || - phy_freq == FREQ_1000_1001(params[freq].phy_freq/10)*10) && + phy_freq == FREQ_1000_1001(params[freq].phy_freq/1000)*1000) && (vclk_freq == params[freq].vclk_freq || vclk_freq == FREQ_1000_1001(params[freq].vclk_freq))) { if (vclk_freq != params[freq].vclk_freq)
