calc_fb_divi...ng_tolerance(9)

✨ calc_fb_divi...ng_tolerance(9) ✨

okay bestie, so this is a page straight out of the Kernel API Manual 📖 and it's literally all about one little function that does Big Math energy for your PLL. Let's get into it 💅

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🎀 NAME 🎀

calc_fb_divider_checking_tolerance — this one calculates the Feedback and Fractional Feedback divider values for the reference divider and post divider you hand it, and the whole time it's doing a tolerance check. basically it's out here doing math and vibe-checking the result at the same time 😭✨

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🌸 SYNOPSIS 🌸

bool calc_fb_divider_checking_tolerance (struct calc_pll_clock_source
*calc_pll_cs , struct pll_settings *pll_settings , uint32_t ref_divider
, uint32_t post_divider , uint32_t tolerance );

it returns a bool, bestie. that's the whole vibe. 🫶

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🦋 ARGUMENTS 🦋

• calc_pll_cs — pointer to the clock source information 👑
• pll_settings — pointer to the PLL settings 💖
• ref_divider — the reference divider (already known, we're not figuring this one out, it's given) ✨
• post_divider — the post divider (also already known, same deal) 🌸
• tolerance — the tolerance that the calculated pixel clock has to stay within. it's giving "how close is close enough" 🎯

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🌈 RETURN 🌈

so here's the tea 🍓 — it fills the PLLSettings structure with the PLL divider values if the calculated values land inside the required tolerance.

then it returns:

• true if the error is within tolerance — slay, we ate 💅🔥
• false if the error is not within tolerance — nope, try again 😭

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👑 SEE ALSO 👑

• Kernel file ./drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c 📂
• calculate_fb_and_fractional_fb_divider(9) — the sibling function, go say hi 🫶

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okay that's the whole page, no cap ✨ this gem lives over in ./drivers/gpu/drm/amd/display/..., it's dated October 2026, and it answers to the name calc_fb_divi...ng_tolerance(9) — periodt 💜🧚