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Message-ID: <9f417fea-38cf-942b-514e-99b47f27c544@quicinc.com>
Date:   Thu, 27 Jul 2023 12:09:07 +0530
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Subject: Re: [PATCH v5 2/2] nvmem: sec-qfprom: Add Qualcomm secure QFPROM
 support
Content-Language: en-US
To:     Komal Bajaj <quic_kbajaj@quicinc.com>, <agross@kernel.org>,
        <andersson@kernel.org>, <konrad.dybcio@linaro.org>,
        <robh+dt@kernel.org>, <krzysztof.kozlowski+dt@linaro.org>,
        <conor+dt@kernel.org>, <srinivas.kandagatla@linaro.org>
CC:     <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20230724083849.8277-1-quic_kbajaj@quicinc.com>
 <20230724083849.8277-3-quic_kbajaj@quicinc.com>
From:   Mukesh Ojha <quic_mojha@quicinc.com>
In-Reply-To: <20230724083849.8277-3-quic_kbajaj@quicinc.com>
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Hi,

Some questions, may not need to be addressed if the reason is
known

On 7/24/2023 2:08 PM, Komal Bajaj wrote:
> For some of the Qualcomm SoC's, it is possible that
> some of the fuse regions or entire qfprom region is
> protected from non-secure access. In such situations,
> Linux will have to use secure calls to read the region.
> With that motivation, add secure qfprom driver.
> 
> Signed-off-by: Komal Bajaj <quic_kbajaj@quicinc.com>
> ---
>   drivers/nvmem/Kconfig      |  13 +++++
>   drivers/nvmem/Makefile     |   2 +
>   drivers/nvmem/sec-qfprom.c | 101 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 116 insertions(+)
>   create mode 100644 drivers/nvmem/sec-qfprom.c
> 
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index b291b27048c7..764fc5feb26c 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -216,6 +216,19 @@ config NVMEM_QCOM_QFPROM
>   	  This driver can also be built as a module. If so, the module
>   	  will be called nvmem_qfprom.
> 
> +config NVMEM_QCOM_SEC_QFPROM
> +        tristate "QCOM SECURE QFPROM Support"
> +        depends on ARCH_QCOM || COMPILE_TEST
> +        depends on HAS_IOMEM
> +        depends on OF
> +        select QCOM_SCM
> +        help
> +          Say y here to enable secure QFPROM support. The secure QFPROM provides access
> +          functions for QFPROM data to rest of the drivers via nvmem interface.
> +
> +          This driver can also be built as a module. If so, the module will be called
> +          nvmem_sec_qfprom.
> +
>   config NVMEM_RAVE_SP_EEPROM
>   	tristate "Rave SP EEPROM Support"
>   	depends on RAVE_SP_CORE
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index f82431ec8aef..e248d3daadf3 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -44,6 +44,8 @@ obj-$(CONFIG_NVMEM_NINTENDO_OTP)	+= nvmem-nintendo-otp.o
>   nvmem-nintendo-otp-y			:= nintendo-otp.o
>   obj-$(CONFIG_NVMEM_QCOM_QFPROM)		+= nvmem_qfprom.o
>   nvmem_qfprom-y				:= qfprom.o
> +obj-$(CONFIG_NVMEM_QCOM_SEC_QFPROM)	+= nvmem_sec_qfprom.o
> +nvmem_sec_qfprom-y			:= sec-qfprom.o

Are we just doing this for just renaming the object ?

>   obj-$(CONFIG_NVMEM_RAVE_SP_EEPROM)	+= nvmem-rave-sp-eeprom.o
>   nvmem-rave-sp-eeprom-y			:= rave-sp-eeprom.o
>   obj-$(CONFIG_NVMEM_RMEM) 		+= nvmem-rmem.o
> diff --git a/drivers/nvmem/sec-qfprom.c b/drivers/nvmem/sec-qfprom.c
> new file mode 100644
> index 000000000000..bc68053b7d94
> --- /dev/null
> +++ b/drivers/nvmem/sec-qfprom.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/firmware/qcom/qcom_scm.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +
> +/**
> + * struct sec_qfprom - structure holding secure qfprom attributes
> + *
> + * @base: starting physical address for secure qfprom corrected address space.
> + * @dev: qfprom device structure.
> + */
> +struct sec_qfprom {
> +	phys_addr_t base;
> +	struct device *dev;
> +};
> +
> +static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
> +{
> +	struct sec_qfprom *priv = context;
> +	unsigned int i;
> +	u8 *val = _val;
> +	u32 read_val;
> +	u8 *tmp;
> +
> +	for (i = 0; i < bytes; i++, reg++) {
> +		if (i == 0 || reg % 4 == 0) {
> +			if (qcom_scm_io_readl(priv->base + (reg & ~3), &read_val)) {
> +				dev_err(priv->dev, "Couldn't access fuse register\n");
> +				return -EINVAL;
> +			}
> +			tmp = (u8 *)&read_val;
> +		}
> +
> +		val[i] = tmp[reg & 3];
> +	}

Getting secure read from fuse region is fine here, since we have to read
4 byte from trustzone, but this restriction of reading is also there
for sm8{4|5}50 soc's where byte by byte reading is protected and 
granularity set to 4 byte (qfprom_reg_read() in drivers/nvmem/qfprom.c)
is will result in abort, in  that case this function need to export this
logic.

> +
> +	return 0;
> +}
> +
> +static int sec_qfprom_probe(struct platform_device *pdev)
> +{
> +	struct nvmem_config econfig = {
> +		.name = "sec-qfprom",
> +		.stride = 1,
> +		.word_size = 1,
> +		.id = NVMEM_DEVID_AUTO,
> +		.reg_read = sec_qfprom_reg_read,
> +	};
> +	struct device *dev = &pdev->dev;
> +	struct nvmem_device *nvmem;
> +	struct sec_qfprom *priv;
> +	struct resource *res;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -EINVAL;
> +
> +	priv->base = res->start;
> +
> +	econfig.size = resource_size(res);
> +	econfig.dev = dev;
> +	econfig.priv = priv;
> +
> +	priv->dev = dev;
> +
> +	ret = devm_pm_runtime_enable(dev);
> +	if (ret)
> +		return ret;
> +
> +	nvmem = devm_nvmem_register(dev, &econfig);
> +
> +	return PTR_ERR_OR_ZERO(nvmem);
> +}
> +
> +static const struct of_device_id sec_qfprom_of_match[] = {
> +	{ .compatible = "qcom,sec-qfprom" },
> +	{/* sentinel */},
> +};
> +MODULE_DEVICE_TABLE(of, sec_qfprom_of_match);
> +
> +static struct platform_driver qfprom_driver = {
> +	.probe = sec_qfprom_probe,

Why don't we have remove/remove_new callbacks?
Same comment apply for drivers/nvmem/qfprom.c

> +	.driver = {
> +		.name = "qcom_sec_qfprom",
> +		.of_match_table = sec_qfprom_of_match,
> +	},
> +};
> +module_platform_driver(qfprom_driver);
> +MODULE_DESCRIPTION("Qualcomm Secure QFPROM driver");
> +MODULE_LICENSE("GPL");
> --
> 2.40.1
> 

-Mukesh