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Wed, 29 Oct 2025 15:21:02 -0400 (EDT) Date: Wed, 29 Oct 2025 20:21:01 +0100 From: Janne Grunau To: Sven Peter Cc: Neal Gompa , Vinod Koul , Kishon Vijay Abraham I , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Philipp Zabel , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-phy@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Alyssa Rosenzweig Subject: Re: [PATCH 1/3] soc: apple: Add hardware tunable support Message-ID: <20251029192101.GA458701@robin.jannau.net> References: <20251026-b4-atcphy-v1-0-f81b1225f9c6@kernel.org> <20251026-b4-atcphy-v1-1-f81b1225f9c6@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20251026-b4-atcphy-v1-1-f81b1225f9c6@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251029_122109_677848_217088A9 X-CRM114-Status: GOOD ( 29.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hej, On Sun, Oct 26, 2025 at 01:52:01PM +0000, Sven Peter wrote: > 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 > Reviewed-by: Neal Gompa > Signed-off-by: Sven Peter > --- > 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 > +#include > +#include > +#include > + > +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), There is a struct_size macro in linux/overflow.h for this calculation. We do not have to care about overflows as as struct property.length remains (signed) int. I would expect there is a much smaller limit for of properties in place anyway. The macro looks nicer though: struct_size(tunable, values, sz) > + 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); Does it make sense to add an size argument either here or in apple_tunable_apply() to check that the offset is within the expect MMIO region? Not really important but might catch a bug someday. > + 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 "); > +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 > +#include > + > +/** > + * 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 Reviewed-by: Janne Grunau Janne