linux-kernel - Re: [PATCH V2] crypto: qcom-rng - Add hw

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Message-ID: <f6a1d8f0-6af3-4e58-8c1b-7d41d46b7ce0@quicinc.com>
Date:   Mon, 25 Sep 2023 16:40:41 +0530
From:   Om Prakash Singh <quic_omprsing@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
CC:     <neil.armstrong@...aro.org>, <konrad.dybcio@...aro.org>,
        <agross@...nel.org>, <andersson@...nel.org>, <conor+dt@...nel.org>,
        <davem@...emloft.net>, <devicetree@...r.kernel.org>,
        <herbert@...dor.apana.org.au>, <krzysztof.kozlowski+dt@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <marijn.suijten@...ainline.org>,
        <robh+dt@...nel.org>, <vkoul@...nel.org>
Subject: Re: [PATCH V2] crypto: qcom-rng - Add hw_random interface support



On 9/22/2023 8:46 PM, Bjorn Andersson wrote:
> On Wed, Sep 20, 2023 at 08:34:08AM +0530, Om Prakash Singh wrote:
>> Add hw_random interface support in qcom-rng driver as new IP block
>> in Qualcomm SoC has inbuilt NIST SP800 90B compliant entropic source
>> to generate true random number.
>>
>> Keeping current rng_alg interface as well for random number generation
>> using Kernel Crypto API.
>>
>> Signed-off-by: Om Prakash Singh <quic_omprsing@...cinc.com>
>> ---
>>
>> Changes in V2:
>> - Updated patch to fix the return value from qcom_rng_generate() to be
>>    consistent with current implementation
> 
> As far as I can tell you didn't change this, see below.
> 
>> - Updated patch to make it more concise
>> - Removed unnecessary use local variable and it's initialization
>> - Updated patch to use devm_hwrng_register() instead of hwrng_register()
>> - Updated subject line of the patch
>>
>> This patch is depends on [1]
>> [1] https://lore.kernel.org/lkml/20230824-topic-sm8550-rng-v2-4-dfcafbb16a3e@linaro.org/
>>
>>   drivers/crypto/qcom-rng.c | 65 ++++++++++++++++++++++++++++++++++-----
>>   1 file changed, 58 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/crypto/qcom-rng.c b/drivers/crypto/qcom-rng.c
>> index fb54b8cfc35f..e5a574a3cc59 100644
>> --- a/drivers/crypto/qcom-rng.c
>> +++ b/drivers/crypto/qcom-rng.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/acpi.h>
>>   #include <linux/clk.h>
>>   #include <linux/crypto.h>
>> +#include <linux/hw_random.h>
>>   #include <linux/io.h>
>>   #include <linux/iopoll.h>
>>   #include <linux/kernel.h>
>> @@ -32,13 +33,18 @@ struct qcom_rng {
>>   	struct mutex lock;
>>   	void __iomem *base;
>>   	struct clk *clk;
>> -	unsigned int skip_init;
>> +	struct qcom_rng_of_data *of_data;
>>   };
>>   
>>   struct qcom_rng_ctx {
>>   	struct qcom_rng *rng;
>>   };
>>   
>> +struct qcom_rng_of_data {
>> +	bool skip_init;
>> +	bool hwrng_support;
>> +};
>> +
>>   static struct qcom_rng *qcom_rng_dev;
>>   
>>   static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
>> @@ -70,7 +76,7 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
>>   		}
>>   	} while (currsize < max);
>>   
>> -	return 0;
>> +	return currsize;
> 
> As I pointed out in my previous review, if the qcom_rng_read() is
> requested to read a number of bytes (max) that is not evenly divisible
> with 4 (WORD_SZ) the loop will exit without accounting for the last
> bytes copied...

I will update implementation to account currsize for accounting 
remaining bytes

>>   }
>>   
>>   static int qcom_rng_generate(struct crypto_rng *tfm,
>> @@ -92,6 +98,9 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
>>   	mutex_unlock(&rng->lock);
>>   	clk_disable_unprepare(rng->clk);
>>   
>> +	if (ret == dlen)
> 
> ...this means that if dlen % 4, you're changing the return value of this
> function from 0 to dlen.

I will Update logic for success case return value.

> 
>> +		ret = 0;
>> +
>>   	return ret;
>>   }
>>   
>> @@ -101,6 +110,13 @@ static int qcom_rng_seed(struct crypto_rng *tfm, const u8 *seed,
>>   	return 0;
>>   }
>>   
>> +static int qcom_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
>> +{
>> +	struct qcom_rng *qrng = (struct qcom_rng *)rng->priv;
> 
> You missed Herbert's request in [1], which I presume implies that
> qcom_hwrng should be moved into struct qcom_rng, which would mean that
> you can get the qrng by container_of().
> 
> [1] https://lore.kernel.org/lkml/ZQQvlXvGy8p01uJS@gondor.apana.org.au/

I will address this comment is my next patch set V3.


>> +
>> +	return qcom_rng_read(qrng, data, max);
>> +}
>> +
>>   static int qcom_rng_enable(struct qcom_rng *rng)
>>   {
>>   	u32 val;
>> @@ -136,7 +152,7 @@ static int qcom_rng_init(struct crypto_tfm *tfm)
>>   
>>   	ctx->rng = qcom_rng_dev;
>>   
>> -	if (!ctx->rng->skip_init)
>> +	if (!ctx->rng->of_data->skip_init)
>>   		return qcom_rng_enable(ctx->rng);
>>   
>>   	return 0;
>> @@ -157,6 +173,12 @@ static struct rng_alg qcom_rng_alg = {
>>   	}
>>   };
>>   
>> +static struct hwrng qcom_hwrng = {
>> +	.name = "qcom-hwrng",
>> +	.read = qcom_hwrng_read,
>> +	.quality = 1024,
>> +};
> 
> Which would mean not adding this static global variable...
> 
> Regards,
> Bjorn