linux-kernel - Re: [PATCH v2 1/2] hwrng: iproc-rng200: Fix disable of the block.

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Message-ID: <c00991f0-c353-c273-de58-a6813ba1fa71@broadcom.com>
Date:   Fri, 18 Dec 2020 09:30:59 -0800
From:   Scott Branden <scott.branden@...adcom.com>
To:     matthias.bgg@...nel.org, mpm@...enic.com,
        herbert@...dor.apana.org.au, rjui@...adcom.com,
        sbranden@...adcom.com, f.fainelli@...il.com
Cc:     linux-kernel@...r.kernel.org, Julia.Lawall@...ia.fr,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org, nsaenzjulienne@...e.de,
        linux-crypto@...r.kernel.org, Matthias Brugger <mbrugger@...e.com>
Subject: Re: [PATCH v2 1/2] hwrng: iproc-rng200: Fix disable of the block.



On 2020-12-18 2:57 a.m., matthias.bgg@...nel.org wrote:
> From: Matthias Brugger <mbrugger@...e.com>
>
> When trying to disable the block we bitwise or the control
> register with value zero. This is confusing as using bitwise or with
> value zero doesn't have any effect at all. Drop this as we already set
> the enable bit to zero by appling inverted RNG_RBGEN_MASK.
>
> Signed-off-by: Matthias Brugger <mbrugger@...e.com>
Acked-by: Scott Branden <scott.branden@...adcom.com>
>
> ---
>
> Changes in v2:
> - fix commit message, dropping Fixes tag
> - drop inverted RNT_RBGEN_ENABLE in disable case
>
>  drivers/char/hw_random/iproc-rng200.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/drivers/char/hw_random/iproc-rng200.c b/drivers/char/hw_random/iproc-rng200.c
> index 01583faf9893..70cd818a0f31 100644
> --- a/drivers/char/hw_random/iproc-rng200.c
> +++ b/drivers/char/hw_random/iproc-rng200.c
> @@ -28,7 +28,6 @@
>  #define RNG_CTRL_OFFSET					0x00
>  #define RNG_CTRL_RNG_RBGEN_MASK				0x00001FFF
>  #define RNG_CTRL_RNG_RBGEN_ENABLE			0x00000001
> -#define RNG_CTRL_RNG_RBGEN_DISABLE			0x00000000
>  
>  #define RNG_SOFT_RESET_OFFSET				0x04
>  #define RNG_SOFT_RESET					0x00000001
> @@ -61,7 +60,6 @@ static void iproc_rng200_restart(void __iomem *rng_base)
>  	/* Disable RBG */
>  	val = ioread32(rng_base + RNG_CTRL_OFFSET);
>  	val &= ~RNG_CTRL_RNG_RBGEN_MASK;
> -	val |= RNG_CTRL_RNG_RBGEN_DISABLE;
>  	iowrite32(val, rng_base + RNG_CTRL_OFFSET);
>  
>  	/* Clear all interrupt status */
> @@ -174,7 +172,6 @@ static void iproc_rng200_cleanup(struct hwrng *rng)
>  	/* Disable RNG hardware */
>  	val = ioread32(priv->base + RNG_CTRL_OFFSET);
>  	val &= ~RNG_CTRL_RNG_RBGEN_MASK;
> -	val |= RNG_CTRL_RNG_RBGEN_DISABLE;
>  	iowrite32(val, priv->base + RNG_CTRL_OFFSET);
>  }
>