Hi Wolfram, On 07/10/2015 12:09 PM, Wolfram Sang wrote: > >> 60 s sounds way too much and actually I simply don't believe this is >> the root cause. If I take a look into the driver, then I see, that > > I agree, this is just a workaround. > >> the design is not really the best. The whole IRQ handling could be >> actually performed in hard IRQ handler, without threading overhead. >> Putting even 2 bytes in the controller FIFO should not be too heavy >> for the hard IRQ handler. Then these ridiculous spin_lock()s. What >> is the reason behind? The IRQ is flagged with ONESHOT, so thread and >> hardirq handler are anyway mutually excluded. But if this thread >> ever runs longer than it's allowed in IRQ context, then it anyway >> produces this IRQ latency because it locks spin_lock_irqsave() for >> the whole time! So the whole point of threaded interrupt is missing. > > Furthermore, this combination of threaded_irq and struct completion seems > bogus to me. If you just want to ensure the irq happened before timeout, > you just complete when the irq happened and do the "bottom half" after the > completion returned? > I'd very appreciated if You would be able to clarify your point a bit, pls? completion is used to indicate end of one message transfer (+check for msg timeout), so .master_xfer()->omap_i2c_xfer could switch to next msg. And there could be more than on IRQ triggered depending on msg length while one message is being transfered. -- regards, -grygorii -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
