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Message-Id: <20251026-b4-atcphy-v1-1-f81b1225f9c6@kernel.org>
Date: Sun, 26 Oct 2025 13:52:01 +0000
From: Sven Peter <sven@...nel.org>
To: Janne Grunau <j@...nau.net>, Neal Gompa <neal@...pa.dev>,
Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, Sven Peter <sven@...nel.org>,
Alyssa Rosenzweig <alyssa@...enzweig.io>
Subject: [PATCH 1/3] soc: apple: Add hardware tunable support
Various hardware, like the Type-C PHY or the Thunderbolt/USB4 NHI,
present on Apple SoCs need machine-specific tunables passed from our
bootloader m1n1 to the device tree. Add generic helpers so that we
don't have to duplicate this across multiple drivers.
Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
Reviewed-by: Neal Gompa <neal@...pa.dev>
Signed-off-by: Sven Peter <sven@...nel.org>
---
drivers/soc/apple/Kconfig | 4 +++
drivers/soc/apple/Makefile | 3 ++
drivers/soc/apple/tunable.c | 71 +++++++++++++++++++++++++++++++++++++++
include/linux/soc/apple/tunable.h | 60 +++++++++++++++++++++++++++++++++
4 files changed, 138 insertions(+)
diff --git a/drivers/soc/apple/Kconfig b/drivers/soc/apple/Kconfig
index ad67368892311bed5a94d358288390a6fb8b3b4a..d0ff32182a2b4a10c98cb96c70a03bea8c650f84 100644
--- a/drivers/soc/apple/Kconfig
+++ b/drivers/soc/apple/Kconfig
@@ -38,6 +38,10 @@ config APPLE_SART
Say 'y' here if you have an Apple SoC.
+config APPLE_TUNABLE
+ tristate
+ depends on ARCH_APPLE || COMPILE_TEST
+
endmenu
endif
diff --git a/drivers/soc/apple/Makefile b/drivers/soc/apple/Makefile
index 4d9ab8f3037b7159771d8817fa507ba29f99ae10..0b85ab61aefe131349a67d0aa80204edd8e89925 100644
--- a/drivers/soc/apple/Makefile
+++ b/drivers/soc/apple/Makefile
@@ -8,3 +8,6 @@ apple-rtkit-y = rtkit.o rtkit-crashlog.o
obj-$(CONFIG_APPLE_SART) += apple-sart.o
apple-sart-y = sart.o
+
+obj-$(CONFIG_APPLE_TUNABLE) += apple-tunable.o
+apple-tunable-y = tunable.o
diff --git a/drivers/soc/apple/tunable.c b/drivers/soc/apple/tunable.c
new file mode 100644
index 0000000000000000000000000000000000000000..c54da8ef28cef16118c518c761f95e8dd9f78002
--- /dev/null
+++ b/drivers/soc/apple/tunable.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple Silicon hardware tunable support
+ *
+ * Each tunable is a list with each entry containing a offset into the MMIO
+ * region, a mask of bits to be cleared and a set of bits to be set. These
+ * tunables are passed along by the previous boot stages and vary from device
+ * to device such that they cannot be hardcoded in the individual drivers.
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/soc/apple/tunable.h>
+
+struct apple_tunable *devm_apple_tunable_parse(struct device *dev,
+ struct device_node *np,
+ const char *name)
+{
+ struct apple_tunable *tunable;
+ struct property *prop;
+ const __be32 *p;
+ size_t sz;
+ int i;
+
+ prop = of_find_property(np, name, NULL);
+ if (!prop)
+ return ERR_PTR(-ENOENT);
+
+ if (prop->length % (3 * sizeof(u32)))
+ return ERR_PTR(-EINVAL);
+ sz = prop->length / (3 * sizeof(u32));
+
+ tunable = devm_kzalloc(dev,
+ sizeof(*tunable) + sz * sizeof(*tunable->values),
+ GFP_KERNEL);
+ if (!tunable)
+ return ERR_PTR(-ENOMEM);
+ tunable->sz = sz;
+
+ for (i = 0, p = NULL; i < tunable->sz; ++i) {
+ p = of_prop_next_u32(prop, p, &tunable->values[i].offset);
+ p = of_prop_next_u32(prop, p, &tunable->values[i].mask);
+ p = of_prop_next_u32(prop, p, &tunable->values[i].value);
+ }
+
+ return tunable;
+}
+EXPORT_SYMBOL(devm_apple_tunable_parse);
+
+void apple_tunable_apply(void __iomem *regs, struct apple_tunable *tunable)
+{
+ size_t i;
+
+ for (i = 0; i < tunable->sz; ++i) {
+ u32 val, old_val;
+
+ val = old_val = readl_relaxed(regs + tunable->values[i].offset);
+ val &= ~tunable->values[i].mask;
+ val |= tunable->values[i].value;
+ if (val != old_val)
+ writel_relaxed(val, regs + tunable->values[i].offset);
+ }
+}
+EXPORT_SYMBOL(apple_tunable_apply);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Sven Peter <sven@...nel.org>");
+MODULE_DESCRIPTION("Apple Silicon hardware tunable support");
diff --git a/include/linux/soc/apple/tunable.h b/include/linux/soc/apple/tunable.h
new file mode 100644
index 0000000000000000000000000000000000000000..7e74e81b32e56c9a8ce94cb64bb340b007bac8da
--- /dev/null
+++ b/include/linux/soc/apple/tunable.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/*
+ * Apple Silicon hardware tunable support
+ *
+ * Each tunable is a list with each entry containing a offset into the MMIO
+ * region, a mask of bits to be cleared and a set of bits to be set. These
+ * tunables are passed along by the previous boot stages and vary from device
+ * to device such that they cannot be hardcoded in the individual drivers.
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#ifndef _LINUX_SOC_APPLE_TUNABLE_H_
+#define _LINUX_SOC_APPLE_TUNABLE_H_
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+/**
+ * Struct to store an Apple Silicon hardware tunable.
+ *
+ * Each tunable is a list with each entry containing a offset into the MMIO
+ * region, a mask of bits to be cleared and a set of bits to be set. These
+ * tunables are passed along by the previous boot stages and vary from device
+ * to device such that they cannot be hardcoded in the individual drivers.
+ *
+ * @param sz Number of [offset, mask, value] tuples stored in values.
+ * @param values [offset, mask, value] array.
+ */
+struct apple_tunable {
+ size_t sz;
+ struct {
+ u32 offset;
+ u32 mask;
+ u32 value;
+ } values[] __counted_by(sz);
+};
+
+/**
+ * Parse an array of hardware tunables from the device tree.
+ *
+ * @dev: Device node used for devm_kzalloc internally.
+ * @np: Device node which contains the tunable array.
+ * @name: Name of the device tree property which contains the tunables.
+ *
+ * @return: devres allocated struct on success or PTR_ERR on failure.
+ */
+struct apple_tunable *devm_apple_tunable_parse(struct device *dev,
+ struct device_node *np,
+ const char *name);
+
+/**
+ * Apply a previously loaded hardware tunable.
+ *
+ * @param regs: MMIO to which the tunable will be applied.
+ * @param tunable: Pointer to the tunable.
+ */
+void apple_tunable_apply(void __iomem *regs, struct apple_tunable *tunable);
+
+#endif
--
2.34.1
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