drm_scdc_set..._clock_ratio(9)

💅 drm_scdc_set_high_tmds_clock_ratio(9) — from the Kernel API Manual, bestie 🎀

okay so picture this: you're deep in the kernel, specifically the DRM/SCDC corner of it, and you need to flip the TMDS clock ratio around. that's literally this whole function. welcome to the group chat 💖

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✨ NAME ✨

drm_scdc_set_high_tmds_clock_ratio — bestie, it sets the TMDS clock ratio. that's the whole vibe check 🦋

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🌸 SYNOPSIS 🌸

bool drm_scdc_set_high_tmds_clock_ratio (struct drm_connector *connector
, bool set );

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🎀 ARGUMENTS 🎀

• connector — the connector. yep. that's it. that's the connector. she's just a connector 🫶
• set — ret or reset the high clock ratio. it's giving "on or off" energy, no further notes 💅

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🔥 DESCRIPTION 🔥

okay so the TMDS clock ratio math is actually kind of iconic once you see it laid out, so let's go, no cap:

• TMDS character = 10 bit TMDS encoded value
• TMDS character rate = the rate at which TMDS characters are transmitted (Mcsc)
• TMDS bit rate = 10x the TMDS character rate

and as per the spec (in case you were wondering, and you were wondering):

• TMDS clock rate for pixel clock < 340 MHz = 1x the character rate = 1/10 pixel clock rate
• TMDS clock rate for pixel clock > 340 MHz = 0.25x the character rate = 1/40 pixel clock rate

so what does the function actually do? she writes to the TMDS config register over the SCDC channel, and then:

• sets the TMDS clock ratio to 1/40 when set = 1
• sets the TMDS clock ratio to 1/10 when set = 0

that's the tea. the whole thing. go off 👑

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⭐ RETURN ⭐

True if the write is successful, false otherwise. literally just vibes: did it work or not 🙈

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/gpu/drm/display/drm_scdc_helper.c
• scdc helpers(9)
• drm_scdc_read(9)
• drm_scdc_write(9)
• drm_scdc_get_scrambling_status(9)
• drm_scdc_set_scrambling(9)

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and that's the whole page, bestie 💜 this little gem lives in ./drivers/gpu/drm/display, and it was dated October 2026 — so go forth and set those clock ratios, mwah 🍓🧚✨