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Message-ID: <ea4c49cd-17d1-6921-a447-5debaebb0cfd@linaro.org>
Date:   Fri, 23 Jun 2023 16:53:44 +0200
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To:     Komal Bajaj <quic_kbajaj@quicinc.com>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>
Cc:     linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
References: <20230623141806.13388-1-quic_kbajaj@quicinc.com>
 <20230623141806.13388-4-quic_kbajaj@quicinc.com>
From:   Konrad Dybcio <konrad.dybcio@linaro.org>
Subject: Re: [PATCH v4 3/6] nvmem: sec-qfprom: Add Qualcomm secure QFPROM
 support.
In-Reply-To: <20230623141806.13388-4-quic_kbajaj@quicinc.com>
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On 23.06.2023 16:18, 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. Ensuring
> the address to read is word aligned since our secure I/O
> only supports word size I/O.
> 
> Signed-off-by: Komal Bajaj <quic_kbajaj@quicinc.com>
> ---
>  drivers/nvmem/Kconfig      |  12 ++++
>  drivers/nvmem/Makefile     |   2 +
>  drivers/nvmem/sec-qfprom.c | 116 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 130 insertions(+)
>  create mode 100644 drivers/nvmem/sec-qfprom.c
> 
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index b291b27048c7..2b0dd73d899e 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -216,6 +216,18 @@ 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
> +        select QCOM_SCM
You also need OF

> +        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..4b4bf5880488 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-$(CONFIG_NVMEM_QCOM_SEC_QFPROM)     += nvmem_sec_qfprom.o
> +nvmem_sec_qfprom-y                          := sec-qfprom.o
>  obj-$(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..47b2c71593dd
> --- /dev/null
> +++ b/drivers/nvmem/sec-qfprom.c
> @@ -0,0 +1,116 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/firmware/qcom/qcom_scm.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_domain.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/property.h>
> +#include <linux/regulator/consumer.h>
> +
> +
> +/**
> + * struct sec_sec_qfprom_priv - structure holding secure qfprom attributes
> + *
> + * @qfpseccorrected: iomapped memory space for secure qfprom corrected address space.
> + * @dev: qfprom device structure.
> + */
> +struct sec_qfprom_priv {
> +	phys_addr_t qfpseccorrected;
> +	struct device *dev;
> +};
> +
> +static int sec_qfprom_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
> +{
> +	struct sec_qfprom_priv *priv = context;
> +	u8 *val = _val;
> +	u8 *tmp;
> +	u32 read_val;
> +	unsigned int i;
Please sort this to look like a reverse-Christmas-tree


> +
> +	for (i = 0; i < bytes; i++, reg++) {
> +		if (i == 0 || reg % 4 == 0) {
> +			if (qcom_scm_io_readl(priv->qfpseccorrected + (reg & ~3), &read_val)) {
> +				dev_err(priv->dev, "Couldn't access fuse register\n");
> +				return -EINVAL;
> +			}
> +			tmp = (u8 *)&read_val;
> +		}
I don't understand this read-4-times dance.. qcom_scm_io_readl() reads
u32, so this should be as simple as:

val[i + 0] = FIELD_GET(GENMASK(7, 0), reg);
val[i + 1] = ..
val[i + 2] = ..
val[i + 3] = ..


> +
> +		val[i] = tmp[reg & 3];
> +	}
> +
> +	return 0;
> +}
> +
> +static void sec_qfprom_runtime_disable(void *data)
> +{
> +	pm_runtime_disable(data);
> +}
> +
> +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 resource *res;
> +	struct nvmem_device *nvmem;
> +	struct sec_qfprom_priv *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	priv->qfpseccorrected = res->start;
> +	if (!priv->qfpseccorrected)
> +		return -ENOMEM;
While it works all the same, I think checking if(!res) would be more
logical

Also, ENOMEM seems weird here.. Perhaps EINVAL?

> +
> +	econfig.size = resource_size(res);
> +	econfig.dev = dev;
> +	econfig.priv = priv;
> +
> +	priv->dev = dev;
> +
> +	pm_runtime_enable(dev);
> +	ret = devm_add_action_or_reset(dev, sec_qfprom_runtime_disable, dev);
> +	if (ret)
> +		return ret;
Wouldn't devm_pm_runtime_enable() take care of this? Or do we need
for this block to be always-powered?

> +
> +	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",},
The comma inside is unnecessary, replacing it with a space would also
make the whitespacing match

> +	{/* sentinel */},
> +};
> +MODULE_DEVICE_TABLE(of, sec_qfprom_of_match);
> +
> +static struct platform_driver qfprom_driver = {
> +	.probe = sec_qfprom_probe,
> +	.driver = {
> +		.name = "qcom,sec_qfprom",
Commas in driver names are rather.. rare? Let's make it qcom_

> +		.of_match_table = sec_qfprom_of_match,
> +	},
> +};
> +module_platform_driver(qfprom_driver);
> +MODULE_DESCRIPTION("Qualcomm Secure QFPROM driver");
> +MODULE_LICENSE("GPL v2");
Please run scripts/checkpatch.pl on your patches before sending.

Konrad