Hi Vineet, > -----Original Message----- > From: Vineet Gupta [mailto:vgupta at synopsys.com] > Sent: Tuesday, January 31, 2017 8:54 PM > To: Yuriy Kolerov <yuriy.kolerov at synopsys.com>; linux-snps- > arc at lists.infradead.org > Cc: marc.zyngier at arm.com; Alexey.Brodkin at synopsys.com; linux- > kernel at vger.kernel.org > Subject: Re: [PATCH v2 4/4] ARCv2: IRQ: Set a default priority for all core > interrupts > > On 01/31/2017 03:45 AM, Yuriy Kolerov wrote: > > After reset all interrupts in the core interrupt controller has the > > highest priority P0. If the platform supports Fast IRQs and has more > > than 1 banks of registers then CPU automatically switch banks of > > registers when P0 interrupt comes. > > > > The problem is that the kernel expects that by default switching of > > banks is not used by all interrupts. It is necessary to set a default > > nonzero priority for all available interrupts to avoid undefined > > behaviour. > > > > Signed-off-by: Yuriy Kolerov <yuriy.kolerov at synopsys.com> > > --- > > arch/arc/kernel/intc-arcv2.c | 12 +++++++++++- > > 1 file changed, 11 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arc/kernel/intc-arcv2.c > > b/arch/arc/kernel/intc-arcv2.c index 31246cc..d4fa4a5 100644 > > --- a/arch/arc/kernel/intc-arcv2.c > > +++ b/arch/arc/kernel/intc-arcv2.c > > @@ -22,7 +22,7 @@ > > */ > > void arc_init_IRQ(void) > > { > > - unsigned int tmp, irq_prio; > > + unsigned int tmp, irq_prio, i; > > > > struct bcr_irq_arcv2 irq_bcr; > > > > @@ -62,6 +62,16 @@ void arc_init_IRQ(void) > > irq_prio + 1, ARCV2_IRQ_DEF_PRIO, > > irq_bcr.firq ? " FIRQ (not used)":""); > > > > + /* > > + * Set a default priority for all available interrupts to prevent > > + * switching of register banks if Fast IRQ and multiple register banks > > + * are supported by CPU. > > + */ > > + for (i = NR_EXCEPTIONS; i < irq_bcr.irqs + NR_EXCEPTIONS; i++) { > > + write_aux_reg(AUX_IRQ_SELECT, i); > > + write_aux_reg(AUX_IRQ_PRIORITY, ARCV2_IRQ_DEF_PRIO); > > + } > > + > > This itself is fine. However going forward can we move to the genirq > irq_cpu_online() etc instead of doing this in our platform per cpu hook ? > > https://www.linux-mips.org/archives/linux-mips/2011-03/msg00115.html We need to set a default priority for all interrupts for each CPU before interrupt controller is configured. In other words it this necessary to guaranty a default state of all interrupts before doing something else with interrupts. Moreover as I understand irq_cpu_online() is intended to be used with virtual IRQs (already allocated interrupts) but the configuration of priorities must be done for all hardware interrupts to bring CPU to the default state. > > /* setup status32, don't enable intr yet as kernel doesn't want */ > > tmp = read_aux_reg(ARC_REG_STATUS32); > > tmp |= STATUS_AD_MASK | (ARCV2_IRQ_DEF_PRIO << 1); > >
