Date: Thu, 01 May 2014 19:17:01 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Winston Smith <smith.winston.101@gmail.com> Cc: FreeBSD ARM <freebsd-arm@FreeBSD.org> Subject: Re: BBB/I2C: Using ioctl(I2CRDWR) warns: interrupt storm detected on "intr70:" Message-ID: <1398993421.22079.160.camel@revolution.hippie.lan> In-Reply-To: <CADH-AwFGiuhcF_xUwQ4n1vkx9u3AJHVf=LMXKotw25NEutm0Vg@mail.gmail.com> References: <CADH-AwGbnqzGqbzpV9YMgdOciLpoy3fqxF1RtCmMPZtgc%2BAcXg@mail.gmail.com> <1398987601.22079.140.camel@revolution.hippie.lan> <CADH-AwFGiuhcF_xUwQ4n1vkx9u3AJHVf=LMXKotw25NEutm0Vg@mail.gmail.com>
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On Thu, 2014-05-01 at 20:24 -0400, Winston Smith wrote: > On Thu, May 1, 2014 at 7:40 PM, Ian Lepore <ian@freebsd.org> wrote: > > Nope, that's not spurious, that's a real problem, usually it's a driver > > bug. > > It happens every time I run my `bbb_eeprom` utility -- how would I go > about further debugging this? Typically an interrupt storm will happen when a device driver's interrupt handler fails to clear the condition that triggers the interrupt, so it re-interrupts immediately, continuously. After spending a few minutes looking at arm/ti/ti_i2c.c, there's something that seems not-quite-right... the interrupt handler reads the I2C_STAT register and clears any interrupt bits it finds there, but: #define I2C_REG_STAT 0x88 When I look in the AM335x reference manual that's listed as "I2C interrupt status vector (legacy)." There's another register at 0x28 described as "Per-event enabled interrupt status vector." I wonder if just changing the I2C_REG_STAT 0x28 (in ti_i2c.h) would fix things? If not, I'd recommend doing a more thorough version of what I started doing... compare what you see in the manual with the code in terms of register offsets and which bits are being checked and see if there are other lurking glitches. -- Ian
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