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f2daf0c67a
Attempting to make use of a 1080p@120Hz display mode with 10 bpc RGB on
my Acer XV275K P3 monitor results in a blank image. A similar behavior
has been reported on Philips 279M1RV.
The faulty modeline is created by drm_gtf_mode_complex() based on the
following EDID entry from the Standard Timings block:
GTF: 1920x1080 119.999987 Hz 16:9 138.840 kHz 368.759000 MHz
It's worth noting the computed pixel clock ends up being slightly higher
at 368.881000 MHz. Nevertheless, this seems to work consistently fine
with 8 bpc RGB.
After switching to 10 bpc, the TMDS character rate expected for the mode
increases to 461.101250 MHz, as per drm_hdmi_compute_mode_clock().
Since there is no entry for this rate in the ropll_tmds_cfg table, the
necessary HDMI PLL configuration parameters are calculated dynamically
by rk_hdptx_phy_clk_pll_calc(). However, the resulting output rate is
not quite a perfect match, i.e. 461.100000 MHz. That proved to be the
actual root cause of the problem.
Add a new entry to the TMDS configuration table and provide the
necessary frequency division coefficients for the PHY PLL to generate
the expected 461.101250 MHz output.
Fixes: 9d0ec51d7c ("phy: rockchip: samsung-hdptx: Add high color depth management")
Tested-by: Derek Foreman <derek.foreman@collabora.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://patch.msgid.link/20251221-phy-hdptx-pll-fix-v2-1-ae4abf7f75a1@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
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