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Date: Fri, 1 May 2020 16:07:39 +0100 From: Steven Price <steven.price@....com> To: Sudeep Holla <sudeep.holla@....com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Cc: Catalin Marinas <Catalin.Marinas@....com>, Will Deacon <will@...nel.org>, Mark Rutland <Mark.Rutland@....com>, Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Harb Abdulhamid (harb@...erecomputing.com)" <harb@...erecomputing.com> Subject: Re: [PATCH 5/5] arm/arm64: smccc: Add ARCH_SOC_ID support On 30/04/2020 12:48, Sudeep Holla wrote: > SMCCC v1.2 adds a new optional function SMCCC_ARCH_SOC_ID to obtain a > SiP defined SoC identification value. Add support for the same. > > Also using the SoC bus infrastructure, let us expose the platform > specific SoC atrributes under sysfs. We also provide custom sysfs for > the vendor ID as JEP-106 bank and identification code. > > Signed-off-by: Sudeep Holla <sudeep.holla@....com> > --- > drivers/firmware/psci/Makefile | 2 +- > drivers/firmware/psci/soc_id.c | 148 +++++++++++++++++++++++++++++++++ > include/linux/arm-smccc.h | 5 ++ > 3 files changed, 154 insertions(+), 1 deletion(-) > create mode 100644 drivers/firmware/psci/soc_id.c > > diff --git a/drivers/firmware/psci/Makefile b/drivers/firmware/psci/Makefile > index 1956b882470f..c0b0c9ca57e4 100644 > --- a/drivers/firmware/psci/Makefile > +++ b/drivers/firmware/psci/Makefile > @@ -1,4 +1,4 @@ > # SPDX-License-Identifier: GPL-2.0 > # > -obj-$(CONFIG_ARM_PSCI_FW) += psci.o > +obj-$(CONFIG_ARM_PSCI_FW) += psci.o soc_id.o > obj-$(CONFIG_ARM_PSCI_CHECKER) += psci_checker.o > diff --git a/drivers/firmware/psci/soc_id.c b/drivers/firmware/psci/soc_id.c > new file mode 100644 > index 000000000000..820f69dad7f5 > --- /dev/null > +++ b/drivers/firmware/psci/soc_id.c > @@ -0,0 +1,148 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright 2020 Arm Limited > + */ > + > +#include <linux/arm-smccc.h> > +#include <linux/bitfield.h> > +#include <linux/device.h> > +#include <linux/module.h> > +#include <linux/kernel.h> > +#include <linux/slab.h> > +#include <linux/sys_soc.h> > + > +#define SOCID_JEP106_BANK_IDX_MASK GENMASK(30, 24) > +#define SOCID_JEP106_ID_CODE_MASK GENMASK(23, 16) > +#define SOCID_IMP_DEF_SOC_ID_MASK GENMASK(15, 0) > +#define JEP106_BANK_IDX(x) (u8)(FIELD_GET(SOCID_JEP106_BANK_IDX_MASK, (x))) > +#define JEP106_ID_CODE(x) (u8)(FIELD_GET(SOCID_JEP106_ID_CODE_MASK, (x))) > +#define IMP_DEF_SOC_ID(x) (u16)(FIELD_GET(SOCID_IMP_DEF_SOC_ID_MASK, (x))) > + > +static int soc_id_version; > +static struct soc_device *soc_dev; > +static struct soc_device_attribute *soc_dev_attr; > + > +static int smccc_map_error_codes(unsigned long a0) > +{ > + if (a0 == SMCCC_RET_INVALID_PARAMETER) > + return -EINVAL; > + if (a0 == SMCCC_RET_NOT_SUPPORTED) > + return -EOPNOTSUPP; > + return 0; It seems odd to special case just those errors. While they are the only errors we expect, any result with the high bit set is an error (arguably a bug in the firmware) so should really cause an error return. > +} > + > +static int smccc_soc_id_support_check(void) > +{ > + struct arm_smccc_res res; > + > + if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) { > + pr_err("%s: invalid SMCCC conduit\n", __func__); > + return -EOPNOTSUPP; > + } > + > + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, > + ARM_SMCCC_ARCH_SOC_ID, &res); > + > + return smccc_map_error_codes(res.a0); > +} > + > +static ssize_t > +jep106_cont_bank_code_show(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + return sprintf(buf, "%02x\n", JEP106_BANK_IDX(soc_id_version) + 1); > +} > + > +static DEVICE_ATTR_RO(jep106_cont_bank_code); > + > +static ssize_t > +jep106_identification_code_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%02x\n", JEP106_ID_CODE(soc_id_version) & 0x7F); It seems odd to have the mask defined to include a bit that is then always masked off. From the spec I presume this is a parity bit, but it would be good to have a comment explaining this. > +} > + > +static DEVICE_ATTR_RO(jep106_identification_code); > + > +static struct attribute *jep106_id_attrs[] = { > + &dev_attr_jep106_cont_bank_code.attr, > + &dev_attr_jep106_identification_code.attr, > + NULL > +}; > + > +ATTRIBUTE_GROUPS(jep106_id); > + > +static int __init smccc_soc_init(void) > +{ > + struct device *dev; > + int ret, soc_id_rev; > + struct arm_smccc_res res; > + static char soc_id_str[8], soc_id_rev_str[12]; > + > + if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_2) > + return 0; NIT: Do we actually need to check the version here - or would probing ARM_SMCCC_ARCH_FEATURES_FUNC_ID as is done below sufficient? I'm not aware of this relying on any new semantics that v1.2 added. > + > + ret = smccc_soc_id_support_check(); > + if (ret) > + return ret; This seems odd - if the version is <v1.2 then we return 0. But if it's >=1.2 but doesn't support SOC_ID then it's an error return? > + > + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 0, &res); > + > + ret = smccc_map_error_codes(res.a0); > + if (ret) > + return ret; > + > + soc_id_version = res.a0; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 1, &res); > + > + ret = smccc_map_error_codes(res.a0); > + if (ret) > + return ret; > + > + soc_id_rev = res.a0; > + > + soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL); > + if (!soc_dev_attr) > + return -ENOMEM; > + > + sprintf(soc_id_str, "0x%04x", IMP_DEF_SOC_ID(soc_id_version)); > + sprintf(soc_id_rev_str, "0x%08x", soc_id_rev); > + > + soc_dev_attr->soc_id = soc_id_str; > + soc_dev_attr->revision = soc_id_rev_str; > + > + soc_dev = soc_device_register(soc_dev_attr); > + if (IS_ERR(soc_dev)) { > + ret = PTR_ERR(soc_dev); > + goto free_soc; > + } > + > + dev = soc_device_to_device(soc_dev); > + > + ret = devm_device_add_groups(dev, jep106_id_groups); > + if (ret) { > + dev_err(dev, "sysfs create failed: %d\n", ret); > + goto unregister_soc; > + } > + > + pr_info("SMCCC SoC ID: %s Revision %s\n", soc_dev_attr->soc_id, > + soc_dev_attr->revision); > + > + return 0; > + > +unregister_soc: > + soc_device_unregister(soc_dev); > +free_soc: > + kfree(soc_dev_attr); > + return ret; > +} > +module_init(smccc_soc_init); > + > +static void __exit smccc_soc_exit(void) > +{ > + if (soc_dev) > + soc_device_unregister(soc_dev); > + kfree(soc_dev_attr); > +} > +module_exit(smccc_soc_exit); > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > index d6b0f4acc707..04414fc2000f 100644 > --- a/include/linux/arm-smccc.h > +++ b/include/linux/arm-smccc.h > @@ -68,6 +68,11 @@ > ARM_SMCCC_SMC_32, \ > 0, 1) > > +#define ARM_SMCCC_ARCH_SOC_ID \ > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ > + ARM_SMCCC_SMC_32, \ > + 0, 2) > + > #define ARM_SMCCC_ARCH_WORKAROUND_1 \ > ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ > ARM_SMCCC_SMC_32, \ >
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