On Wed, 27 Nov 2019 at 14:09, Pete Batard <p...@akeo.ie> wrote: > > On 2019.11.27 13:00, Ard Biesheuvel wrote: > > On Wed, 27 Nov 2019 at 13:56, Pete Batard <p...@akeo.ie> wrote: > >> > >> On 2019.11.27 12:48, Ard Biesheuvel wrote: > >>> On Wed, 27 Nov 2019 at 13:37, Pete Batard <p...@akeo.ie> wrote: > >>>> > >>>> Add missing RNG registers, prefer reusing shorter define's > >>>> instead of PCDs and clean up spacing. > >>>> > >>> > >>> Is there a source for these register definitions? > >> > >> I used the most recent Linux driver I could find (but I guess I need to > >> point out that it was used for reference with regards to the registers. > >> Especially, no code was copied from that source). > >> > >>> It seems the Linux > >>> driver deviates from the below (and the warmup count thing uses the > >>> status register as well), so it would be helpful to quote the > >>> authoritative reference here. > >> > >> https://github.com/raspberrypi/linux/blob/rpi-5.4.y/drivers/char/hw_random/iproc-rng200.c#L223-L224 > >> seems to indicate that RNG_WARMUP_COUNT (0x40000) should go into > >> RNG_TOTAL_BIT_COUNT_THRESHOLD_OFFSET (them) / RNG_BIT_COUNT_THRESHOLD > >> (us) and not the status register. > >> > >> Now, of course, since we don't have a public datasheet, it's hard to > >> have absolute certainty on what's the proper register to write, but I > >> guess the most recent code with a Broadcom Corporation copyright has to > >> our next best thing when it comes to authoritative answer... > >> > > > > Well, there is this one too > > > > https://github.com/raspberrypi/linux/blob/rpi-5.4.y/drivers/char/hw_random/bcm2835-rng.c > > > > which is what I used as the basis for the existing version. > > Okay. Looks like 2835 (which has to be the basis for the Bcm2837 used on > the Pi 3) and 2838 (basis for Bcm2711) have at least one difference with > regards to where the warmup count should go. > > I guess an easy fix, if we don't want to have to spin 2 separate > drivers, is to write to both RNG_STATUS and RNG_BIT_COUNT_THRESHOLD > during init. > > I have tested on Pi 3 and not seen any ill effect to writing to > RNG_BIT_COUNT_THRESHOLD. >
I don't like that at all tbh. A misbehaving RNG is virtually undetectable (unless it starts returning zeroes), so knowingly deviating from the initialization routines like that should really be avoided. > Would something like this work for you in a v2? > > Alternatively, I could change the new PcdBcm283xRngUseFifo PCD to > PcdBcm283xRng2838Compatible and use that for the conditional code. > These are two different IP blocks, with different register layouts etc, so I don't really see the point in parameterizing the existing driver like that. I'd prefer it if we could just clone the existing one and make the changes unconditionally. -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#51346): https://edk2.groups.io/g/devel/message/51346 Mute This Topic: https://groups.io/mt/62504739/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
