Hi Marc, can you please look into my last comments ?
Regards, Bharat > Subject: RE: [PATCH v5] PCI: Xilinx NWL: Modifying irq chip for legacy > interrupts > > Waiting for Marc's Reply... > > > > -----Original Message----- > > > From: Marc Zyngier [mailto:marc.zyng...@arm.com] > > > Sent: Thursday, February 09, 2017 9:33 PM > > > To: Bharat Kumar Gogada <bhara...@xilinx.com>; bhelg...@google.com; > > > r...@kernel.org; paul.gortma...@windriver.com; > > > colin.k...@canonical.com; linux-...@vger.kernel.org > > > Cc: linux-arm-ker...@lists.infradead.org; > > > linux-kernel@vger.kernel.org; michal.si...@xilinx.com; > > > a...@arndb.de; Ravikiran Gummaluri <rgum...@xilinx.com> > > > 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
