14.06.2019 12:50, Bitan Biswas пишет: > > > On 6/13/19 5:28 AM, Dmitry Osipenko wrote: >> 13.06.2019 14:30, Bitan Biswas пишет: >>> >>> >>> On 6/12/19 7:30 AM, Dmitry Osipenko wrote: >>>> 11.06.2019 13:51, Bitan Biswas пишет: >>>>> Fix expression for residual bytes(less than word) transfer >>>>> in I2C PIO mode RX/TX. >>>>> >>>>> Signed-off-by: Bitan Biswas <bbiswas@xxxxxxxxxx> >>>>> --- >>>> >>>> [snip] >>>> >>>>> /* >>>>> - * Update state before writing to FIFO. If this casues us >>>>> + * Update state before writing to FIFO. If this causes us >>>>> * to finish writing all bytes (AKA buf_remaining goes to >>>>> 0) we >>>>> * have a potential for an interrupt (PACKET_XFER_COMPLETE is >>>>> - * not maskable). We need to make sure that the isr sees >>>>> - * buf_remaining as 0 and doesn't call us back re-entrantly. >>>>> + * not maskable). >>>>> */ >>>>> buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD; >>>> >>>> Looks like the comment could be removed altogether because it doesn't >>>> make sense since interrupt handler is under xfer_lock which is kept >>>> locked during of tegra_i2c_xfer_msg(). >>> I would push a separate patch to remove this comment because of >>> xfer_lock in ISR now. >>> >>>> >>>> Moreover the comment says that "PACKET_XFER_COMPLETE is not maskable", >>>> but then what I2C_INT_PACKET_XFER_COMPLETE masking does? >>>> >>> I2C_INT_PACKET_XFER_COMPLETE masking support available in Tegra chips >>> newer than Tegra30 allows one to not see interrupt after Packet transfer >>> complete. With the xfer_lock in ISR the scenario discussed in comment >>> can be ignored. >> >> Also note that xfer_lock could be removed and replaced with a just >> irq_enable/disable() calls in tegra_i2c_xfer_msg() because we only care >> about IRQ not firing during of the preparation process. > This should need sufficient testing hence let us do it in a different series. I don't think that there is much to test here since obviously it should work. >> >> It also looks like tegra_i2c_[un]nmask_irq isn't really needed and all >> IRQ's could be simply unmasked during the driver's probe, in that case >> it may worth to add a kind of "in-progress" flag to catch erroneous >> interrupts. >> > TX interrupt needs special handling if this change is done. Hence I think it should be > taken up after sufficient testing in a separate patch. This one is indeed a bit more trickier. Probably another alternative could be to keep GIC interrupt disabled while no transfer is performed, then you'll have to request interrupt in a disabled state using IRQ_NOAUTOEN flag. And yes, that all should be a separate changes if you're going to implement them.
