Enable shared GPIO for Apple Silicon audio support

Hi folks,

On Apple Silicon Macs, every speaker codec's software shutdown pin is connected to the same GPIO line. This line must be pulled high whenever any codec asserts it so.

This makes power management impossible. When we goe through the list of codecs and call each suspend/resume, the GPIO line is asserted low or high by the first suspended/resumed codec. This causes issues for the subsequent codecs; they are already shut off by the time we try to cache the register state on suspend.

In the downstream Asahi Linux kernel[1], we were previously (ab)using the regulator API to work around this safely. We replaced the shutdown-gpios property in the codec Devicetree nodes with a virtual regulator which acts as a proxy for the GPIO line. The regulator will not deassert the pin until every consumer wants it off, and it will assert it as soon as any one codec requires it.

Now that the kernel has shared GPIO support, this has become unnecessary. The first commit in this series enables shared GPIO for ARCH_APPLE so that we can take advantage of this new(ish) infrastructure.

The shared GPIO infrastructure considers the first state change of a line to be the "default" state, which is the state that it will allow to be asserted without all consumers agreeing. Currently the TAS2764 and TAS2770 drivers initialise the shutdown GPIO high, which means the first change is to low. This does not help us, as the line will not be reasserted on resume until all codecs have tried to assert it. Since both drivers explicitly pull the line high on codec probe, we can initialise it low, causing the first state change to be from low to high. This makes the shared GPIO proxy behave as we intend. The second and third commits in this series implement this.

This has been enabled in the Asahi Linux kernel since 7.1.9, and addresses the last obstacle to attempting to upstream the machine driver for this platform.

We intend to take the Kconfig patch via our soc tree. The two codec driver changes should be taken via asoc.

Regards,
James

[1] https://github.com/AsahiLinux/linux

---
James Calligeros (3):
arm64: Kconfig: Select HAVE_SHARED_GPIOS for Apple Silicon
ASoC: tas2764: Initialise SDZ GPIO low
ASoC: tas2770: Initialise SDZ GPIO low

 arch/arm64/Kconfig.platforms | 1 +
 sound/soc/codecs/tas2764.c   | 2 +-
 sound/soc/codecs/tas2770.c   | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

---
base-commit: cf72cbb39da84b6f02f90c07f33b102fc10b16f0
change-id: 20260829-apple-shared-gpio-60f86e74e35a

Best regards,

James Calligeros <[email protected]>

Apple Silicon Macs use a shared GPIO line for all speaker codec shutdown pins.

Select HAVE_SHARED_GPIOS for ARCH_APPLE so that we can use the shared GPIO proxy infrastructure for this.

---
 arch/arm64/Kconfig.platforms | 1 +
 1 file changed, 1 insertion(+)

index d2acfac73003..76a6a0e6ae4f 100644
@@ -37,6 +37,7 @@ config ARCH_APPLE
 	bool "Apple Silicon SoC family"
 	select APPLE_AIC
 	select APPLE_PMGR_PWRSTATE if PM
+	select HAVE_SHARED_GPIOS
 	help
 	  This enables support for Apple's in-house ARM SoC family, such
 	  as the Apple M1.

2.55.0

On Apple Silicon machines integrating TAS2764, the SDZ pin of all codecs is connected to a shared GPIO line. The kernel's shared GPIO infrastructure relies on the first change of the GPIO state being marked as its "default" state, and allows any consumer of the shared line to assert that state without consensus from other consumers.

If the pin is initialised high, the shared GPIO core does not allow the line to be asserted without consensus. This breaks resuming from suspend on Apple Silicon machines; the driver attempts to restore the codec's register state and fails because other codecs are still holding the line low.

Initialise the SDZ GPIO low so that the first state change on probe asserts it high, allowing any codec to pull the line up when it needs to.

---
 sound/soc/codecs/tas2764.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index f9c65c9f6d0a..b3c08d106dd7 100644
@@ -960,7 +960,7 @@ static int tas2764_parse_dt(struct device *dev, struct tas2764_priv *tas2764)
 		}
 	}
 
-	tas2764->sdz_gpio = devm_gpiod_get_optional(dev, "shutdown", GPIOD_OUT_HIGH);
+	tas2764->sdz_gpio = devm_gpiod_get_optional(dev, "shutdown", GPIOD_OUT_LOW);
 	if (IS_ERR(tas2764->sdz_gpio)) {
 		if (PTR_ERR(tas2764->sdz_gpio) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;

2.55.0

On Apple Silicon machines integrating TAS2770, the SDZ pin of all codecs is connected to a shared GPIO line. The kernel's shared GPIO infrastructure relies on the first change of the GPIO state being marked as its "default" state, and allows any consumer of the shared line to assert that state without consensus from other consumers.

If the pin is initialised high, the shared GPIO core does not allow the line to be asserted without consensus. This breaks resuming from suspend on Apple Silicon machines; the driver attempts to restore the codec's register state and fails because other codecs are still holding the line low.

Initialise the SDZ GPIO low so that the first state change on probe asserts it high, allowing any codec to pull the line up when it needs to.

---
 sound/soc/codecs/tas2770.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index e79754edac5c..ecc37d4ac00b 100644
@@ -886,7 +886,7 @@ static int tas2770_parse_dt(struct device *dev, struct tas2770_priv *tas2770)
 	if (rc)
 		tas2770->pdm_slot = -1;
 
-	tas2770->sdz_gpio = devm_gpiod_get_optional(dev, "shutdown", GPIOD_OUT_HIGH);
+	tas2770->sdz_gpio = devm_gpiod_get_optional(dev, "shutdown", GPIOD_OUT_LOW);
 	if (IS_ERR(tas2770->sdz_gpio)) {
 		if (PTR_ERR(tas2770->sdz_gpio) == -EPROBE_DEFER)
 			return -EPROBE_DEFER;

2.55.0

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.4

Thanks!

[2/3] ASoC: tas2764: Initialise SDZ GPIO low

      https://git.kernel.org/broonie/sound/c/e152ac60589b
[3/3] ASoC: tas2770: Initialise SDZ GPIO low
      https://git.kernel.org/broonie/sound/c/87e41baa36fc

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying to this mail.

Thanks,
Mark

Applied to [email protected]:AsahiLinux/linux.git (apple-soc/drivers-7.4), thanks!

[1/3] arm64: Kconfig: Select HAVE_SHARED_GPIOS for Apple Silicon

      https://github.com/AsahiLinux/linux/commit/a416a347931f

Best regards,

Sven Peter <[email protected]>