TL-WR1043: switch

[Aleksandr Rybalko]

Hi,

On Wed, 30 Nov 2011 12:58:14 -0700
Warner Losh <imp at bsdimp.com> wrote:

> 
> On Nov 30, 2011, at 12:43 PM, Stefan Bethke wrote:
> 
> > One step closer:
> > 
> > http://www.lassitu.de/freebsd/rtl8366ctl.tbz
> > 
> > The starting point for a configuration utility.  I've implemented
> > two "drivers": direct bitbanging access via gpio(4), or I2C access
> > via iic(4).
> > 
> > The I2C framework makes a faulty assumption that the read/not-write
> > bit of the first byte (the address) indicates whether reads or
> > writes are to follow.  While many simple I2C devices usually will
> > follow this rule, it's not prescribed by the protocol (AFAICT), and
> > is incompatible with the way the RTL8366 familiy uses the bus:
> > after sending the address+read/not-write byte, two register address
> > bytes are sent, then the 16-bit register value is sent or
> > received.  While the register write access can be performed as a
> > 4-byte write, the read access requires the read bit to be set, but
> > the first two bytes for the register address then need to be
> > transmitted.

Now I recall my problems with iic :)

> 
> I thought that was spelled out in the i2c spec fairly clearly...  Do
> you have the data sheet showing this timing?
> 

I found the same in other Realtek switches, that rules applied also to
RTL8367, 8370.
IIRC Realtek even don't name this bus as I2C :)
This usage maybe related with use of this bus to access i2c EEPROM for
initialization. 

> Warner
> 
> > This patch removes the faulty check:
> > Index: sys/dev/iicbus/iiconf.c
> > ===================================================================
> > --- sys/dev/iicbus/iiconf.c	(revision 228073)
> > +++ sys/dev/iicbus/iiconf.c	(working copy)
> > @@ -244,7 +244,7 @@
> > 	struct iicbus_softc *sc = (struct iicbus_softc
> > *)device_get_softc(bus); 
> > 	/* a slave must have been started with the appropriate
> > address */
> > -	if (!sc->started || (sc->started & LSB))
> > +	if (!sc->started)
> > 		return (EINVAL);
> > 
> > 	return (IICBUS_WRITE(device_get_parent(bus), buf, len,
> > sent, timeout)); @@ -262,7 +262,7 @@
> > 	struct iicbus_softc *sc = (struct iicbus_softc
> > *)device_get_softc(bus); 
> > 	/* a slave must have been started with the appropriate
> > address */
> > -	if (!sc->started || !(sc->started & LSB))
> > +	if (!sc->started)
> > 		return (EINVAL);
> > 
> > 	return (IICBUS_READ(device_get_parent(bus), buf, len, read,
> > last, delay));
> > 
> > While trying to figure this out, I also came across the panic in
> > sys/dev/gpio/gpiobus.c:panic("rb_cpldbus: cannot serialize the
> > access to device.").  I'm not sure how I triggered it (the
> > backtrace wasn't immediately revealing to me), but I'm speculating
> > that the I2C fails to relinquish the GPIO when a bus transaction is
> > aborted.
> > 
> > 
> > Stefan
> > 
> > -- 
> > Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811
> > 
> > 
> > 
> > _______________________________________________
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> > 
> > 
> 
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-- 
Aleksandr Rybalko <ray at ddteam.net>