i2c almost working for me, was Re: i2c still not working for me

[Ian Lepore]

On Thu, 2019-04-18 at 10:12 +0300, Daniel Braniss wrote:
> > On 17 Apr 2019, at 23:26, Emmanuel Vadot <manu at bidouilliste.com>
> > wrote:
> > 
> > On Tue, 16 Apr 2019 09:16:02 +0300
> > Daniel Braniss <danny at cs.huji.ac.il <mailto:danny at cs.huji.ac.il>>
> > wrote:
> > 
> > > 
> > > 
> > > > On 11 Apr 2019, at 09:56, Daniel Braniss <danny at cs.huji.ac.il>
> > > > wrote:
> > > > 
> > > > if no device is connected, I2CRDWR hangs, 
> > > > it also happens with i2c(8) -s, only reboot helps.
> > > > 
> > > > ichb1: twsi_reset: Using IIC_FASTEST/UNKNOWN mode with speed
> > > > param=2a
> > > > iichb1: TWSI_WRITE: Writing 0 to 18
> > > > iichb1: TWSI_WRITE: Writing 2a to 14
> > > > iichb1: TWSI_WRITE: Writing 40 to c
> > > > iichb1: TWSI_WRITE: Writing c4 to c
> > > > iichb1: twsi_transfer: transmitting 2 messages
> > > > iichb1: TWSI_READ: read f8 from 10
> > > > iichb1: twsi_transfer: status=f8
> > > > iichb1: twsi_transfer: msg[0] flags: 0
> > > > iichb1: twsi_transfer: msg[0] len: 9
> > > > iichb1: TWSI_WRITE: Writing e4 to c
> > > > 
> > > > and now it?s hung
> > > 
> > > [?]
> > 
> > I don't see that on my OrangePi One or Pine64-LTS.
> 
> well, mine is are Nanopi Neo, maybe it’s a dts issue?
> I also have a orangepi-zero but it will take me some time to make
> a sdcard
> > 
> > > 
> > > even with a working device, this happens sometimes:
> > > 
> > > my app gets ENXIO from the ioctl(fd, I2CRDWR, &data) and on the
> > > console:
> > > ?
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 38 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > gic0: Spurious interrupt detected: last irq: 29 on CPU2
> > > 
> > > the good news: my app is killable :-)
> > 
> > I would need more details for this.
> 
> it was caused by i2c issues - the cable was a bit too long.
> BTW, does changing the frequency work? ie dev.iicbus.0.frequency

It looks like that driver does not honor the frequency sysctl/tunable.

You can often compensate for a too-long cable by adding some stronger
pullups.  It's typical for a SOM to have pullups in the 4.7K range on
i2c.  You can add your own 1K pullups to see if that helps the rise
times on the bus.

-- Ian