Date:   Mon, 4 May 2020 15:49:59 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Steven Price <steven.price@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        linux-kernel@...r.kernel.org, harb@...erecomputing.com
Subject: Re: [PATCH v2 5/5] arm/arm64: smccc: Add ARCH_SOC_ID support

On Mon, May 04, 2020 at 03:10:23PM +0100, Steven Price wrote:
> On 04/05/2020 10:29, 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>
> 
> Some minor things below, but with those fixed:
> 
> Reviewed-by: Steven Price <steven.price@....com>
> 
> > ---
> >   drivers/firmware/psci/Kconfig  |   9 ++
> >   drivers/firmware/psci/Makefile |   1 +
> >   drivers/firmware/psci/soc_id.c | 165 +++++++++++++++++++++++++++++++++
> >   include/linux/arm-smccc.h      |   5 +
> >   4 files changed, 180 insertions(+)
> >   create mode 100644 drivers/firmware/psci/soc_id.c
> > 
> > diff --git a/drivers/firmware/psci/Kconfig b/drivers/firmware/psci/Kconfig
> > index 97944168b5e6..831399338289 100644
> > --- a/drivers/firmware/psci/Kconfig
> > +++ b/drivers/firmware/psci/Kconfig
> > @@ -12,3 +12,12 @@ config ARM_PSCI_CHECKER
> >   	  The torture tests may interfere with the PSCI checker by turning CPUs
> >   	  on and off through hotplug, so for now torture tests and PSCI checker
> >   	  are mutually exclusive.
> > +
> > +config ARM_SMCCC_SOC_ID
> > +	bool "SoC bus device for the ARM SMCCC SOC_ID"
> > +	depends on ARM_PSCI_FW
> > +	default y if ARM_PSCI_FW
> 
> Since it depends on ARM_PSCI_FW this "if" part is not needed.
> 

Indeed, I was experimenting something and forgot to remove it.

> > +	select SOC_BUS
> > +	help
> > +	  Include support for the SoC bus on the ARM SMCCC firmware based
> > +	  platforms providing some sysfs information about the SoC variant.
> > diff --git a/drivers/firmware/psci/Makefile b/drivers/firmware/psci/Makefile
> > index 1956b882470f..55596698d1ad 100644
> > --- a/drivers/firmware/psci/Makefile
> > +++ b/drivers/firmware/psci/Makefile
> > @@ -2,3 +2,4 @@
> >   #
> >   obj-$(CONFIG_ARM_PSCI_FW)	+= psci.o
> >   obj-$(CONFIG_ARM_PSCI_CHECKER)	+= psci_checker.o
> > +obj-$(CONFIG_ARM_SMCCC_SOC_ID)	+= soc_id.o
> > diff --git a/drivers/firmware/psci/soc_id.c b/drivers/firmware/psci/soc_id.c
> > new file mode 100644
> > index 000000000000..b45f2d78e12e
> > --- /dev/null
> > +++ b/drivers/firmware/psci/soc_id.c
> > @@ -0,0 +1,165 @@
> > +// 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 SMCCC_SOC_ID_JEP106_BANK_IDX_MASK	GENMASK(30, 24)
> > +/*
> > + * As per the spec bits[23:16] are JEP-106 identification code with parity bit
> > + * for the SiP. We can drop the parity bit.
> > + */
> > +#define SMCCC_SOC_ID_JEP106_ID_CODE_MASK	GENMASK(22, 16)
> > +#define SMCCC_SOC_ID_IMP_DEF_SOC_ID_MASK	GENMASK(15, 0)
> > +
> > +/* The bank index is equal to the for continuation code bank number - 1 */
> > +#define JEP106_BANK_CONT_CODE(x)	\
> > +	(u8)(FIELD_GET(SMCCC_SOC_ID_JEP106_BANK_IDX_MASK, (x)) + 1)
> > +#define JEP106_ID_CODE(x)	\
> > +	(u8)(FIELD_GET(SMCCC_SOC_ID_JEP106_ID_CODE_MASK, (x)))
> > +#define IMP_DEF_SOC_ID(x)	\
> > +	(u16)(FIELD_GET(SMCCC_SOC_ID_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_SUCCESS)
> > +		return 0;
> > +	else if (a0 == SMCCC_RET_INVALID_PARAMETER)
> > +		return -EINVAL;
> > +	else if (a0 == SMCCC_RET_NOT_SUPPORTED)
> > +		return -EOPNOTSUPP;
> > +	return -EINVAL;
> > +}
> > +
> > +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_CONT_CODE(soc_id_version));
> > +}
> > +
> > +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));
> > +}
> > +
> > +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;
> > +
> > +	ret = smccc_soc_id_support_check();
> > +	if (ret) {
> > +		pr_info("SMCCC SOC_ID not implemented, skipping ....\n");
> > +		return 0;
> > +	}
> > +
> > +	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 0, &res);
> > +
> > +	ret = smccc_map_error_codes(res.a0);
> > +	if (ret) {
> > +		pr_info("SMCCC SOC_ID: failed to version, Err = %d\n", ret);
>                                                 ^ get/fetch
> > +		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) {
> > +		pr_info("SMCCC SOC_ID: failed to revision, Err = %d\n", ret);
>                                                 ^ get/fetch

Will fix it.

> > +		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);
> 
> All these pr_info()s have (almost) the same initial string, it might be
> worth defining pr_fmt() and dropping it from the individual calls.
> 

Makes sense, will do that. Thanks again for the review.

-- 
Regards,
Sudeep

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