On Thu, Feb 16, 2023 at 12:32:10PM +0100, Matthias Brugger wrote: > > > On 16/02/2023 11:03, AngeloGioacchino Del Regno wrote: > > Il 15/02/23 14:27, Daniel Golle ha scritto: > > > Add driver providing kernel-side support for the Random Number > > > Generator hardware found on Mediatek SoCs which have a driver in ARM > > > TrustedFirmware-A allowing Linux to read random numbers using a > > > non-standard vendor-defined Secure Monitor Call. > > > > > > Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx> > > > > Hello Daniel, > > > > incidentally, I've also done some research on this one some months ago, when > > I was deep in adding support for the Helio X10 SoC (MT6795) on Xperia M5. > > > > The rng-v2 is simply the same rng but hypervised by the TF-A... and the only > > difference is, well, as you're also pointing out, that we're using secure > > monitor calls instead of direct MMIO handling. > > > > There's also not much more than what you've implemented here and the only kind > > of addition that we will ever see on this one will be about changing the SIP > > command (as some older SoCs use a different one)... so... > > > > ...I don't think that adding an entirely new driver is worth the noise, hence > > I propose to simply add handling for the Secure RNG to mtk-rng.c instead: it's > > shorter and we would only need to address one if branch on that probe function > > to set a different callback. > > > > The clock should then be optional for *some* of those "v2 handling" devices, > > as if I recall correctly, some do need the clock to be handled from Linux > > anyway... otherwise this v2 driver will be "soon" looking bloody similar to > > the "v1", adding a bit of code duplication around. > > > > What do you think? > > > > That was exactly what I was thinking as well when I had a look at the > driver. I propose to add it to mtk-rng.c. I don't see any value having a > second driver for this. Or fix the firmware to use the already defined SMC TRNG interface... In any case, like the SMC TRNG, you don't need a DT binding. The firmware interface is discoverable. Try the SMC call and if it succeeds, you have a TRNG. Rob > > Regards, > Matthias > > > Regards, > > Angelo > > > > > --- > > > MAINTAINERS | 1 + > > > drivers/char/hw_random/Kconfig | 16 +++++++ > > > drivers/char/hw_random/Makefile | 1 + > > > drivers/char/hw_random/mtk-rng-v2.c | 74 +++++++++++++++++++++++++++++ > > > 4 files changed, 92 insertions(+) > > > create mode 100644 drivers/char/hw_random/mtk-rng-v2.c > > > > >
