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Message-ID: <6b6eb47c-b1fa-8621-5b83-9adb4918b932@quicinc.com>
Date:   Thu, 1 Jun 2023 17:00:11 +0530
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Subject: Re: [PATCH v3 01/10] nvmem: qfprom: Add support for secure reading
Content-Language: en-US
To:     Bjorn Andersson <andersson@kernel.org>
CC:     Andy Gross <agross@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.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>,
        <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>
References: <20230512122134.24339-1-quic_kbajaj@quicinc.com>
 <20230512122134.24339-2-quic_kbajaj@quicinc.com>
 <20230527205031.iwsujvlbxazukwfy@ripper>
From:   Komal Bajaj <quic_kbajaj@quicinc.com>
In-Reply-To: <20230527205031.iwsujvlbxazukwfy@ripper>
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On 5/28/2023 2:20 AM, Bjorn Andersson wrote:
> On Fri, May 12, 2023 at 05:51:25PM +0530, 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 the support of reading secure
>> regions in 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  |  1 +
>>   drivers/nvmem/qfprom.c | 69 +++++++++++++++++++++++++++++++++---------
>>   2 files changed, 55 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
>> index b291b27048c7..3d896ba29b89 100644
>> --- a/drivers/nvmem/Kconfig
>> +++ b/drivers/nvmem/Kconfig
>> @@ -209,6 +209,7 @@ config NVMEM_QCOM_QFPROM
>>   	tristate "QCOM QFPROM Support"
>>   	depends on ARCH_QCOM || COMPILE_TEST
>>   	depends on HAS_IOMEM
>> +	select QCOM_SCM
>>   	help
>>   	  Say y here to enable QFPROM support. The QFPROM provides access
>>   	  functions for QFPROM data to rest of the drivers via nvmem interface.
>> diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
>> index c1e893c8a247..20662e2d3732 100644
>> --- a/drivers/nvmem/qfprom.c
>> +++ b/drivers/nvmem/qfprom.c
>> @@ -16,6 +16,7 @@
>>   #include <linux/pm_runtime.h>
>>   #include <linux/property.h>
>>   #include <linux/regulator/consumer.h>
>> +#include <linux/firmware/qcom/qcom_scm.h>
>>
>>   /* Blow timer clock frequency in Mhz */
>>   #define QFPROM_BLOW_TIMER_OFFSET 0x03c
>> @@ -59,21 +60,22 @@ struct qfprom_soc_data {
>>   /**
>>    * struct qfprom_priv - structure holding qfprom attributes
>>    *
>> - * @qfpraw:       iomapped memory space for qfprom-efuse raw address space.
>> - * @qfpconf:      iomapped memory space for qfprom-efuse configuration address
>> - *                space.
>> + * @qfpraw: iomapped memory space for qfprom-efuse raw address space.
>> + * @qfpconf: iomapped memory space for qfprom-efuse configuration address space.
> Adjusting the indentation makes it unnecessarily hard to see what you
> actually changed.
Okay, will maintain the existing indentation.
>
>>    * @qfpcorrected: iomapped memory space for qfprom corrected address space.
>> - * @qfpsecurity:  iomapped memory space for qfprom security control space.
>> - * @dev:          qfprom device structure.
>> - * @secclk:       Clock supply.
>> - * @vcc:          Regulator supply.
>> - * @soc_data:     Data that for things that varies from SoC to SoC.
>> + * @qfpsecurity: iomapped memory space for qfprom security control space.
>> + * @qfpseccorrected: starting physical address for qfprom secure corrected address space.
>> + * @dev: qfprom device structure.
>> + * @secclk: Clock supply.
>> + * @vcc: Regulator supply.
>> + * @soc_data: Data that for things that varies from SoC to SoC.
>>    */
>>   struct qfprom_priv {
>>   	void __iomem *qfpraw;
>>   	void __iomem *qfpconf;
>>   	void __iomem *qfpcorrected;
>>   	void __iomem *qfpsecurity;
>> +	phys_addr_t qfpseccorrected;
>>   	struct device *dev;
>>   	struct clk *secclk;
>>   	struct regulator *vcc;
>> @@ -99,10 +101,12 @@ struct qfprom_touched_values {
>>    *
>>    * @keepout: Array of keepout regions for this SoC.
>>    * @nkeepout: Number of elements in the keepout array.
>> + * @secure: Is qfprom region for this SoC protected from non-secure access.
>>    */
>>   struct qfprom_soc_compatible_data {
>>   	const struct nvmem_keepout *keepout;
>>   	unsigned int nkeepout;
>> +	bool secure;
>>   };
>>
>>   static const struct nvmem_keepout sc7180_qfprom_keepout[] = {
>> @@ -334,6 +338,34 @@ static int qfprom_reg_read(void *context,
>>   	return 0;
>>   }
>>
>> +static int qfprom_sec_reg_read(void *context, unsigned int reg, void *_val, size_t bytes)
>> +{
>> +	struct qfprom_priv *priv = context;
>> +	u8 *val = _val;
>> +	int buf_start, buf_end, index, i = 0;
>> +	char *buffer;
>> +	u32 read_val;
>> +
>> +	buf_start = ALIGN_DOWN(reg, 4);
>> +	buf_end = ALIGN(reg + bytes, 4);
>> +	buffer = kzalloc(buf_end - buf_start, GFP_KERNEL);
>> +	if (!buffer)
>> +		return -ENOMEM;
> I don't you need all these variables, the full temp buffer or the two
> memcpy... I think something like this should do the trick:
>
> 	unsigned int i;
> 	u8 *val = _val;
> 	u8 tmp[4];
>
> 	for (i = 0; i < bytes; i++, reg++)
> 		if (i == 0 || reg % 4 == 0)
> 			qcom_scm_io_readl(qfpseccorrected + (reg & ~3), tmp);
>
> 		val[i] = tmp[reg & 3];
> 	}
Thanks, for this. Will make the suggested change in the next patch series.
>> +
>> +	for (index = buf_start; index < buf_end; index += 4, i += 4) {
>> +		if (qcom_scm_io_readl(priv->qfpseccorrected + index, &read_val)) {
>> +			dev_err(priv->dev, "Couldn't access feature register\n");
> What's a "feature register"?
It's a fuse register that we are trying to read here.

Thanks
Komal

>
> Regards,
> Bjorn
>
>> +			kfree_sensitive(buffer);
>> +			return -EINVAL;
>> +		}
>> +		memcpy(buffer + i, &read_val, 4);
>> +	}
>> +
>> +	memcpy(val, buffer + reg % 4, bytes);
>> +	kfree_sensitive(buffer);
>> +	return 0;
>> +}
>> +
>>   static void qfprom_runtime_disable(void *data)
>>   {
>>   	pm_runtime_disable(data);
>> @@ -373,13 +405,6 @@ static int qfprom_probe(struct platform_device *pdev)
>>   	if (!priv)
>>   		return -ENOMEM;
>>
>> -	/* The corrected section is always provided */
>> -	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> -	priv->qfpcorrected = devm_ioremap_resource(dev, res);
>> -	if (IS_ERR(priv->qfpcorrected))
>> -		return PTR_ERR(priv->qfpcorrected);
>> -
>> -	econfig.size = resource_size(res);
>>   	econfig.dev = dev;
>>   	econfig.priv = priv;
>>
>> @@ -390,6 +415,20 @@ static int qfprom_probe(struct platform_device *pdev)
>>   		econfig.nkeepout = soc_data->nkeepout;
>>   	}
>>
>> +	/* The corrected section is always provided */
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +
>> +	if (soc_data && soc_data->secure) {
>> +		priv->qfpseccorrected = res->start;
>> +		econfig.reg_read = qfprom_sec_reg_read;
>> +	} else {
>> +		priv->qfpcorrected = devm_ioremap_resource(dev, res);
>> +		if (IS_ERR(priv->qfpcorrected))
>> +			return PTR_ERR(priv->qfpcorrected);
>> +	}
>> +
>> +	econfig.size = resource_size(res);
>> +
>>   	/*
>>   	 * If more than one region is provided then the OS has the ability
>>   	 * to write.
>> --
>> 2.17.1
>>