> -----Original Message----- > From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] > Sent: Thursday, February 09, 2017 9:33 PM > To: Bharat Kumar Gogada <bharatku@xxxxxxxxxx>; bhelgaas@xxxxxxxxxx; > robh@xxxxxxxxxx; paul.gortmaker@xxxxxxxxxxxxx; colin.king@xxxxxxxxxxxxx; > linux-pci@xxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > michal.simek@xxxxxxxxxx; arnd@xxxxxxxx; Ravikiran Gummaluri > <rgummal@xxxxxxxxxx> > Subject: Re: [PATCH v5] PCI: Xilinx NWL: Modifying irq chip for legacy interrupts > > On 09/02/17 15:16, Bharat Kumar Gogada wrote: > >> > >> On 09/02/17 12:01, Bharat Kumar Gogada wrote: > >>>> On 06/02/17 07:03, Bharat Kumar Gogada wrote: > >>>>> +static struct irq_chip nwl_leg_irq_chip = { > >>>>> + .name = "nwl_pcie:legacy", > >>>>> + .irq_enable = nwl_unmask_leg_irq, > >>>>> + .irq_disable = nwl_mask_leg_irq, > >>>> > >>>> You don't need these two if they are implemented in terms of > mask/unmask. > >>> > >>> These are being invoked by some drivers other than interrupt flow. > >>> Ex: drivers/net/wireless/ath/ath9k/main.c > >>> static int ath_reset_internal(struct ath_softc *sc, struct > >>> ath9k_channel *hchan) { > >>> .... > >>> disable_irq(sc->irq); > >>> tasklet_disable(&sc->intr_tq); > >>> ... > >>> ... > >>> enable_irq(sc->irq); > >>> spin_unlock_bh(&sc->sc_pcu_lock); } For us masking/unmasking > >>> is the way to enable/disable interrupts. > >> > >> And if you looked at the way disable_irq is implemented, you would > >> have found out that it falls back to masking if there is no disable > >> method, preserving the semantic you expect. > >> > > Yes I did see, but this fall back requires extra "IRQ_DISABLE_UNLAZY" flag to > be set to each virq. > > No it doesn't. If you do a disable_irq(), the interrupt is flagged as disabled, but > nothing gets done. If an interrupt actually fires, then the interrupts gets masked, > and the handler is not called. Yes agreed, this is where the problem comes for us. Here is the scenario Ex:drivers/net/wireless/ath/ath9k/main.c static int ath_reset_internal(struct ath_softc *sc, struct ath9k_channel *hchan) { .... ath9k_hw_set_interrupts(ah); ath9k_hw_enable_interrupts(ah); ... enable_irq(sc->irq); ... } If you observe this they enable hardware interrupts first and then call enable_irq, at this point of time virq is in disabled state. So, if interrupt is raised in this period of time the handler is never invoked and DEASEERT_INTx will not be seen. As I mentioned in my subject the irq line between bridge and GIC goes low only after it sees DEASSERT_INTx. But since DEASSERT_INTx is never seen line is always high causing cpu stall. So for this kind of EP's we need those two methods. Bharat
