Hi Douglas, On Thu, Jan 01, 2015 at 01:02:13PM -0500, Douglas Gilbert wrote: > With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I > connected a NXP SC16IS750 I2C to serial bridge. After > routing the 750's IRQ back to the sc16is7xx driver and some > simple successful test, it was time for some intense testing: > Tx looped back to Rx on the 750, open picocom on /dev/ttySC0 > at 38400, and use hexdump to blast a binary file (in hex) at > ttySC0. The I2C SCL speed was 200,000 Hz. > > It worked as expected for a few seconds then it wedged the > I2C bus. That was repeatable. In the cases that I checked SCL > was high, SDA was low (driven by _both_ the G25's macrocell > and the 750!!) and IRQ was active (low). This patch stopped > the G25 macrocell from driving SDA low in the above wedge > (and stopped copious error reports going to the log). I was > surprised that a NXP I2C chip got into this situation, IMO > SDA on a slave should have a driven low timeout. IMO all > I2C master drivers should have provision to drive a gpio > connected to a (or all the) slave's RESET line(s). > > > ChangeLog: > when handling an I2C bus time-out, first clean-up the > DMA transfer, then do an I2C macrocell software reset > and restore some registers, including the interrupt > mask >
I am wondering why you need to call at91_twi_irq_save() and at91_twi_irq_restore(). The interrupts enabled in the driver are AT91_TWI_TXCOMP, AT91_TWI_RXRDY and AT91_TWI_TXRDY and they are managed in at91_do_twi_transfer() so they would be set correctly for the next transfer. Regards Ludovic > Signed-off-by: Douglas Gilbert <[email protected]> > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c > index 636fd2e..4d78708 100644 > --- a/drivers/i2c/busses/i2c-at91.c > +++ b/drivers/i2c/busses/i2c-at91.c > @@ -382,6 +382,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > { > int ret; > bool has_unre_flag = dev->pdata->has_unre_flag; > + bool timed_out = false; > > dev_dbg(dev->dev, "transfer: %s %d bytes.\n", > (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len); > @@ -440,7 +441,7 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > dev->adapter.timeout); > if (ret == 0) { > dev_err(dev->dev, "controller timed out\n"); > - at91_init_twi_bus(dev); > + timed_out = true; > ret = -ETIMEDOUT; > goto error; > } > @@ -471,6 +472,11 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) > > error: > at91_twi_dma_cleanup(dev); > + if (timed_out) { > + at91_twi_irq_save(dev); > + at91_init_twi_bus(dev); > + at91_twi_irq_restore(dev); > + } > return ret; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
