STRUCT CS4270_MODE_RATIOS(9)

📦 version 7.3.1, in nixpkgs unstable

✨ struct cs4270_mode_ratios(9) ✨

okay so bestie, welcome to the kernel API manual 💅 — today we're looking at struct cs4270_mode_ratios, and honestly? it's giving "small struct, big responsibilities." no cap.

🎀 NAME 🎀

struct cs4270_mode_ratios — clock ratio tables, fr fr 🕰️✨

🦋 SYNOPSIS 🦋

struct cs4270_mode_ratios {
    unsigned int ratio;
    u8 speed_mode;
    u8 mclk;
 };

like, that's the whole struct. three fields. iconic minimalism 💜

🌸 Members 🌸

  • ratio — the ratio of MCLK to the sample rate. it's literally the math-y one 🧮
  • speed_mode — the Speed Mode bits you gotta set in the Mode Control register for this ratio 🔥
  • mclk — the Ratio Select bits to set in the Mode Control register for this ratio 🎯

👑 Description 👑

okay so the data for this chart is taken from Table 5 of the CS4270 reference manual — so like, not us making it up, that's canon 📖✨

This table is used to determine how to program the Mode Control register. It's also used by cs4270_set_dai_sysclk to tell ALSA which sampling rates the CS4270 currently supports. so yeah, it's double-booked and it's thriving 🫶

  • speed_mode is the corresponding bit pattern to be written to the MODE bits of the Mode Control Register
  • mclk is the corresponding bit pattern to be wirten to the MCLK bits of the Mode Control Register.
ngl that "wirten" is a typo that lives in the source and I'm not fixing it, we respect our elders 🙈 (also written, bestie, it means written 💀)

In situations where a single ratio is represented by multiple speed modes, we favor the slowest speed. E.g, for a ratio of 128, we pick double-speed instead of quad-speed. lowkey a whole lifestyle choice — slow and steady, main character energy 🐢✨ However, the CS4270 errata states that divide-By-1.5 can cause failures, so we avoid that mode where possible. 🚨

Errata: There is an errata for the CS4270 where divide-by-1.5 does not work if Vd is 3.3V. If this effects you, select the CONFIG_SND_SOC_CS4270_VD33_ERRATA Kconfig option, and the driver will never select any sample rates that require divide-by-1.5. like, ever. periodt. 💅⚠️

🌈 SEE ALSO 🌈

Kernel file ./sound/soc/codecs/cs4270.c plus the whole friend group:

and that's the page!! 🍓 this lil love letter to the CS4270 lives in ./sound/soc/codecs, dated October 2026, and it's part of the Kernel API Manual — stay hydrated, read your errata, and slay your Mode Control register 💖🎀💅

📦 where this page comes from