linux-kernel - Re: [PATCH v2 2/2] hwrng: msm

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Date:   Tue, 19 Jun 2018 15:11:33 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Vinod Koul <vinod.koul@...aro.org>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH v2 2/2] hwrng: msm - Add support for prng v2

Hi Vinod,

On 06/19/2018 12:54 PM, Vinod Koul wrote:
> Qcom 8996 and later chips support prng v2 which requires to
> implement only .read callback for hwrng.
> 
> This version of chip has multiple Execution Environments (EE) and
> secure world is typically responsible for configuring the prng.
> 
> Add driver data for qcom,prng as 0 and qcom,prng-v2 as 1 and use
> that to skip initialization and cleanup routines.
> 
> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> ---
>  drivers/char/hw_random/msm-rng.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/hw_random/msm-rng.c b/drivers/char/hw_random/msm-rng.c
> index 841fee845ec9..4676520e1f16 100644
> --- a/drivers/char/hw_random/msm-rng.c
> +++ b/drivers/char/hw_random/msm-rng.c
> @@ -17,6 +17,7 @@
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  
>  /* Device specific register offsets */
> @@ -131,6 +132,7 @@ static int msm_rng_probe(struct platform_device *pdev)
>  {
>  	struct resource *res;
>  	struct msm_rng *rng;
> +	unsigned int skip_init;
>  	int ret;
>  
>  	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
> @@ -149,9 +151,12 @@ static int msm_rng_probe(struct platform_device *pdev)
>  		return PTR_ERR(rng->clk);
>  
>  	rng->hwrng.name = KBUILD_MODNAME,
> -	rng->hwrng.init = msm_rng_init,
> -	rng->hwrng.cleanup = msm_rng_cleanup,
> -	rng->hwrng.read = msm_rng_read,
> +	rng->hwrng.read = msm_rng_read;
> +	skip_init = (unsigned long)of_device_get_match_data(&pdev->dev);

skip_init is unsigned int, despite I think you don't need to cast it.

> +	if (!skip_init) {
> +		rng->hwrng.init = msm_rng_init;
> +		rng->hwrng.cleanup = msm_rng_cleanup;
> +	}
>  
>  	ret = devm_hwrng_register(&pdev->dev, &rng->hwrng);
>  	if (ret) {
> @@ -163,7 +168,8 @@ static int msm_rng_probe(struct platform_device *pdev)
>  }
>  
>  static const struct of_device_id msm_rng_of_match[] = {
> -	{ .compatible = "qcom,prng", },
> +	{ .compatible = "qcom,prng", .data = (void *)0},
> +	{ .compatible = "qcom,prng-v2", .data = (void *)1},

No need to cast. IMO it'd be better to create defines for these numbers:

#define PRNG_V1	0
#define PRNG_V2	1


-- 
regards,
Stan