Messages in this thread | | | Date | Fri, 1 May 2020 16:57:29 +0100 | From | Sudeep Holla <> | Subject | Re: [PATCH 5/5] arm/arm64: smccc: Add ARCH_SOC_ID support |
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Hi Steve,
Thanks for taking a reviewing these patches.
On Fri, May 01, 2020 at 04:07:39PM +0100, Steven Price wrote: > 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@arm.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. >
I agree and happy to change it. I too thought about the same for a while and they left it for review time to finalise 😄
> > +} > > + > > +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. >
Sure, actually I can to make it part of the macro itself and add a note there.
> > +} > > + > > +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. >
It should be sufficient, but I am trying to avoid raising error if it is not SMCCC v1.2+, hence the return 0.
> > + > > + 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? >
You are right, I see that now. I can flag a note/info and return 0.
-- Regards, Sudeep
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