On Monday 05 August 2013 09:44 PM, Joel Fernandes wrote: > We certainly don't want error conditions to be cleared any other > place but the EDMA error handler, as this will make us 'forget' > about missed events we might need to know errors have occurred. > > This fixes a race condition where the EMR was being cleared > by the transfer completion interrupt handler. > > Basically, what was happening was: > > Missed event > | > | > V > SG1-SG2-SG3-Null > \ > \__TC Interrupt (Almost same time as ARM is executing > TC interrupt handler, an event got missed and also forgotten > by clearing the EMR). > > This causes the following problems: > > 1. > If error interrupt is also pending and TC interrupt clears the EMR > by calling edma_stop as has been observed in the edma_callback function, > the ARM will execute the error interrupt even though the EMR is clear. > As a result, the dma_ccerr_handler returns IRQ_NONE. If this happens > enough number of times, IRQ subsystem disables the interrupt thinking > its spurious which makes error handler never execute again. > > 2. > Also even if error handler doesn't return IRQ_NONE, the removing of EMR > removes the knowledge about which channel had a missed event, and thus > a manual trigger on such channels cannot be performed. > > The EMR is ultimately being cleared by the Error interrupt handler > once it is handled so we remove code that does it in edma_stop and > allow it to happen there. > > Signed-off-by: Joel Fernandes <joelf@xxxxxx> Queuing this for v3.11 fixes. While committing, I changed the headline to remove capitalization and made it more readable by removing register level details. The new headline is: ARM: edma: don't clear missed events in edma_stop() Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
