Date: Tue, 12 Sep 2017 16:52:01 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 222256] RPI random number generator underruns when BCM2835_RNG_USE_CALLOUT is set Message-ID: <bug-222256-8-5iVNqAzy82@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-222256-8@https.bugs.freebsd.org/bugzilla/> References: <bug-222256-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222256 --- Comment #2 from Stephen J. Kiernan <stevek@freebsd.org> --- Interesting. The RPi3 must be a bit different than the RPi2 (where the initial testing using callout was done.) It might make sense to have a sysctl in the case where one would want to use the callout version to be able to tweak it as appropriate. However, it's better to use the default interrupt method rather than the callout, because, as you saw, there can be cases where the random bit generator (RBG) cannot provide enough bits to satisfy a request, if the callout period is too short. With the interrupt method, the RBG is programmed to raise an interrupt when the FIFO is full. When that occurs, the interrupt handler reads from the FIFO and feeds the bits read into the random_harvest_queue function. However, that requires the FDT for the board to have a proper entry for the RBG with an interrupt attribute, which I don't think the RPi3 FDT has currently. -- You are receiving this mail because: You are the assignee for the bug.
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