> -----Original Message----- > From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > Sent: 9 January, 2023 11:04 AM > To: JiaJie Ho <jiajie.ho@xxxxxxxxxxxxxxxx> > Cc: Olivia Mackall <olivia@xxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; > Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Emil Renner > Berthing <kernel@xxxxxxxx>; Conor Dooley <conor.dooley@xxxxxxxxxxxxx>; > linux-crypto@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; linux-riscv@xxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive > SoC > > On Mon, Jan 09, 2023 at 02:58:14AM +0000, JiaJie Ho wrote: > > > > My trng device requires sending a generate new number cmd before each > read. > > It then only populates the data registers with new random number and > raise an interrupt when ready. > > If user choose to not wait, they will always get stale bits. > > Is it okay to always return error if wait=false ? > > What is the length of the wait time? Is there an upper bound? > What is the average wait time? > The average wait time is around 20 microseconds. I measured from writel cmd to wait_for_completion done. Thanks Jia Jie
