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Date:   Mon, 9 Jan 2023 12:00:20 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
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" <linux-crypto@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC
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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?

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.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt