samsung_gpio_pm_2bit_resume(9)

💅 samsung_gpio_pm_2bit_resume — from the Kernel API Manual, bestie ✨

okay so picture this: it's samsung_gpio_pm_2bit_resume(9) and she's the function that gets your GPIO bank back on its feet after a lil nap 💤 — full breakdown below, no cap 🫶

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✨ NAME ✨

samsung_gpio_pm_2bit_resume — restore the given GPIO bank, slay 💖

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🦋 SYNOPSIS 🦋

void samsung_gpio_pm_2bit_resume (struct samsung_gpio_chip *chip );

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🎀 ARGUMENTS 🎀

• chip — the chip information to resume. that's the whole vibe she needs to wake up 🌸

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👑 DESCRIPTION 👑

So she restores one of the GPIO banks that was saved during suspend ✨. Easy, right? NOT. This is not as simple as once thought, because there's a real possibility of glitches depending on the order that the CON and DAT registers are set in 😭 — yes the order literally matters, iykyk.

The three states the pin can be in are {IN,OUT,SFN}, which gives us 9 combinations of changes to check 🔥. Three of these, if the pin stays in the same configuration, can be discounted (we don't need those, they're giving "nothing to see here" energy 💅). That leaves us with the following, and honestly? iconic:

• { IN => OUT } — Change DAT first
• { IN => SFN } — Change CON first
• { OUT => SFN } — Change CON first, so new data will not glitch
• { OUT => IN } — Change CON first, so new data will not glitch
• { SFN => IN } — Change CON first
• { SFN => OUT } — Change DAT first, so new data will not glitch [1]

We do not currently deal with the UP registers, because these control weak resistors 🍓 — so a small delay in change should not need to bring these into the calculations. she's just not in her era yet, and that's fine 🙈.

[1] this assumes that writing to a pin DAT whilst in SFN will set the state for when it is next output ⭐

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🌈 SEE ALSO 🌈

Kernel file ./arch/arm/mach-s3c/pm-gpio.c plus the whole friend group 🫶: samsung_pm_save_gpio(9), samsung_pm_save_gpios(9), samsung_pm_resume_gpio(9)

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and that's the tea 💜 — this one's from ./arch/arm/mach-s3c, dated October 2026, and it's literally the samsung_gpio_pm_2bit_resume(9) page. go off, kernel documentation ✨🎀💅