Messages in this thread | | | From | JiaJie Ho <> | Subject | RE: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC | Date | Mon, 9 Jan 2023 04:33:26 +0000 |
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> -----Original Message----- > From: Herbert Xu <herbert@gondor.apana.org.au> > Sent: 9 January, 2023 12:00 PM > To: JiaJie Ho <jiajie.ho@starfivetech.com> > Cc: Olivia Mackall <olivia@selenic.com>; Rob Herring <robh+dt@kernel.org>; > Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>; Emil Renner > Berthing <kernel@esmil.dk>; Conor Dooley <conor.dooley@microchip.com>; > linux-crypto@vger.kernel.org; devicetree@vger.kernel.org; linux- > kernel@vger.kernel.org; linux-riscv@lists.infradead.org > Subject: Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive > SoC > > On Mon, Jan 09, 2023 at 03:41:14AM +0000, JiaJie Ho wrote: > > > > The average wait time is around 20 microseconds. > > I measured from writel cmd to wait_for_completion done. > > Do you know of an upper bound? E.g., if we limit it to 40us how many > requests would fail on average? >
I don't have the upper bound. I ran the rngtest with 1000 blocks, none of the wait time exceeded 30us.
> Having a maximum delay of 40us would be OK with wait == 0. So you could > implement it in a way such that if the wait time exceeded 40us then you > return if wait == 0, otherwise you can wait longer. >
I'll do this then.
Thanks Jia Jie
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