On 2019-02-11 09:31, Federico Vaga wrote: > Detecting a timeout is ok, but we also need to assert a STOP command on > the bus in order to prevent it from generating interrupts when there are > no on going transfers. > > Example: very long transmission. > > 1. ocores_xfer: START a transfer > 2. ocores_isr : handle byte by byte the transfer > 3. ocores_xfer: goes in timeout [[bugfix here]] > 4. ocores_xfer: return to I2C subsystem and to the I2C driver > 5. I2C driver : it may clean up the i2c_msg memory > 6. ocores_isr : receives another interrupt (pending bytes to be > transferred) but the i2c_msg memory is invalid now > > So, since the transfer was too long, we have to detect the timeout and > STOP the transfer. > > Another point is that we have a critical region here. When handling the > timeout condition we may have a running IRQ handler. For this reason I > introduce a spinlock. > > In order to make easier to understan locking I have: > - added a new function to handle timeout > - modified the current ocores_process() function in order to be protected > by the new spinlock > Like this it is obvious at first sight that this locking serializes > the execution of ocores_process() and ocores_process_timeout() > *snip* > @@ -184,14 +197,14 @@ static void ocores_process(struct ocores_i2c *i2c) > > oc_setreg(i2c, OCI2C_DATA, addr); > oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START); Didn't checkpatch complain about the double space? Fixing it fits in patch 5... Cheers, Peter
