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=3D222256 --- Comment #2 from Stephen J. Kiernan <stevek@freebsd.org> --- Interesting. The RPi3 must be a bit different than the RPi2 (where the init= ial 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 gener= ator (RBG) cannot provide enough bits to satisfy a request, if the callout perio= d 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 re= ads from the FIFO and feeds the bits read into the random_harvest_queue functio= n. 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. --=20 You are receiving this mail because: You are the assignee for the bug.=
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