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Date: Wed, 12 Feb 2020 21:54:51 +0530 From: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com> To: Martin Kaiser <martin@...ser.cx> Cc: Herbert Xu <herbert@...dor.apana.org.au>, NXP Linux Team <linux-imx@....com>, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" <linux-crypto@...r.kernel.org>, linux-arm-kernel@...ts.infradead.org, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/6] hwrng: imx-rngc - use automatic seeding On Tue, 28 Jan 2020 at 16:31, Martin Kaiser <martin@...ser.cx> wrote: > > The rngc requires a new seed for its prng after generating 2^20 160-bit > words of random data. At the moment, we seed the prng only once during > initalisation. > > Set the rngc to auto seed mode so that it kicks off the internal > reseeding operation when a new seed is required. > > Keep the manual calculation of the initial seed when the device is > probed and switch to automatic seeding afterwards. > > Signed-off-by: Martin Kaiser <martin@...ser.cx> > --- > drivers/char/hw_random/imx-rngc.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c > index 0576801944fd..903894518c8d 100644 > --- a/drivers/char/hw_random/imx-rngc.c > +++ b/drivers/char/hw_random/imx-rngc.c > @@ -31,6 +31,7 @@ > > #define RNGC_CTRL_MASK_ERROR 0x00000040 > #define RNGC_CTRL_MASK_DONE 0x00000020 > +#define RNGC_CTRL_AUTO_SEED 0x00000010 > > #define RNGC_STATUS_ERROR 0x00010000 > #define RNGC_STATUS_FIFO_LEVEL_MASK 0x00000f00 > @@ -167,7 +168,7 @@ static irqreturn_t imx_rngc_irq(int irq, void *priv) > static int imx_rngc_init(struct hwrng *rng) > { > struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng); > - u32 cmd; > + u32 cmd, ctrl; > int ret; > > /* clear error */ > @@ -192,7 +193,18 @@ static int imx_rngc_init(struct hwrng *rng) > > } while (rngc->err_reg == RNGC_ERROR_STATUS_STAT_ERR); > > - return rngc->err_reg ? -EIO : 0; > + if (rngc->err_reg) > + return -EIO; > + > + /* > + * enable automatic seeding, the rngc creates a new seed automatically > + * after serving 2^20 random 160-bit words > + */ > + ctrl = readl(rngc->base + RNGC_CONTROL); > + ctrl |= RNGC_CTRL_AUTO_SEED; > + writel(ctrl, rngc->base + RNGC_CONTROL); > + > + return 0; > } > > static int imx_rngc_probe(struct platform_device *pdev) > -- > 2.20.1 > Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
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