Hi,Felipe, I'd very appreciate if you'd be able to provide the use case
On Tue, Jul 16, 2013 at 05:33:47PM +0800, Hein Tibosch wrote:On 7/16/2013 5:03 PM, Felipe Balbi wrote:Hi,
On Tue, Jul 16, 2013 at 04:19:35PM +0800, Hein Tibosch wrote:Hi Vikram,patch below breaks repeated start.
On a OMAP4460, i2c-bus-3:
A driver (lm75) is causing many 'timeout waiting for bus ready' errors.
SDA remains high (as it should), but SCL remains low after a NACK.
The bus becomes _unusable for other clients_.
While probing, "lm75" writes a command, followed by a read + stop,
but the write command is NACK'd. The chip does accept other writes/reads,
it just refuses to ack invalid commands.
Can you tell me if the patch below would make any sense? Or is it the
responsibility of the client to reset the i2c_smbus?
I think, this is valid fix, but it was done here already:)Hi,
No, after the NACK, no more commands are being processed,
including a repeated start. omap_i2c_xfer() returns -EREMOTEIO
without ever freeing the bus.
The bus is left in an impossible state with SCL constantly low
and all next commands (to different chips) will therefore get
a -ETIMEDOUT
With this patch, the bus will become idle again and new commands
can be processed normally
but you mentioned that if you have IGNORE_NAK set, everything is fine,
since lm75 will get a return value of 0 and things will work just fine,
right ?
Also, you also said that the chip 'refuses to ack invalid commands', why
are you sending invalid commands to start with ? This could be a bug in
i2c-omap.c, sure, but let's try to figure out why IGNORE_NAK helps and
why is lm75 driver sending invalid commands.