| Message ID | 0958510b69cf679fef64ccf535b1cdc43c5ffccc.1449572109.git.nsekhar@ti.com |
|---|---|
| State | Superseded |
| Headers | show |
Hi, Sekhar Nori <nsekhar@ti.com> writes: > Under some conditions, irq sorting procedure used > by INTC can go wrong resulting in a spurious irq > getting reported. > > If this condition is not handled, it results in > endless stream of: > > unexpected IRQ trap at vector 00 > > messages from ack_bad_irq() > > Handle the spurious interrupt condition in omap-intc > driver to prevent this. > > Signed-off-by: Sekhar Nori <nsekhar@ti.com> > --- > v2: increment error irq counter, use pr_err_once, > add a comment on tips to debug spurious irq > condition. > > This patch results in a checkpatch warning about > extern definition of irq_err_count, but looks like > thats the prevalent method of accessing that counter. > > drivers/irqchip/irq-omap-intc.c | 27 ++++++++++++++++++++++++++- > 1 file changed, 26 insertions(+), 1 deletion(-) > > diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c > index 8587d0f8d8c0..639708de5529 100644 > --- a/drivers/irqchip/irq-omap-intc.c > +++ b/drivers/irqchip/irq-omap-intc.c > @@ -47,6 +47,7 @@ > #define INTC_ILR0 0x0100 > > #define ACTIVEIRQ_MASK 0x7f /* omap2/3 active interrupt bits */ > +#define SPURIOUSIRQ_MASK (0x1ffffff << 7) > #define INTCPS_NR_ILR_REGS 128 > #define INTCPS_NR_MIR_REGS 4 > > @@ -330,11 +331,35 @@ static int __init omap_init_irq(u32 base, struct device_node *node) > static asmlinkage void __exception_irq_entry > omap_intc_handle_irq(struct pt_regs *regs) > { > + extern unsigned long irq_err_count; > u32 irqnr; > > irqnr = intc_readl(INTC_SIR); > + > + /* > + * A spurious IRQ can result if interrupt that triggered the > + * sorting is no longer active during the sorting (10 INTC > + * functional clock cycles after interrupt assertion). Or a > + * change in interrupt mask affected the result during sorting > + * time. There is no special handling required except ignoring > + * the SIR register value just read and retrying. > + * See section 6.2.5 of AM335x TRM Literature Number: SPRUH73K > + * > + * Many a times, a spurious interrupt situation has been fixed > + * by adding a flush for the posted write acking the IRQ in > + * the device driver. Typically, this is going be the device > + * driver whose interrupt was handled just before the spurious > + * IRQ occurred. Pay attention to those device drivers if you > + * run into hitting the spurious IRQ condition below. > + */ > + if ((irqnr & SPURIOUSIRQ_MASK) == SPURIOUSIRQ_MASK) { sounds like unlikely() wouldn't hurt here. > + pr_err_once("%s: spurious irq!\n", __func__); > + irq_err_count++; > + omap_ack_irq(NULL); > + return; > + } > + > irqnr &= ACTIVEIRQ_MASK; > - WARN_ONCE(!irqnr, "Spurious IRQ ?\n"); > handle_domain_irq(domain, irqnr, regs); care to run kernel function profiler against omap_intc_handle_irq() before and after this patch ? -- balbi
On Thursday 10 December 2015 08:46 PM, Sekhar Nori wrote: > Hi Felipe, > > On Tuesday 08 December 2015 07:15 PM, Felipe Balbi wrote: >> Sekhar Nori <nsekhar@ti.com> writes: > >>> + /* >>> + * A spurious IRQ can result if interrupt that triggered the >>> + * sorting is no longer active during the sorting (10 INTC >>> + * functional clock cycles after interrupt assertion). Or a >>> + * change in interrupt mask affected the result during sorting >>> + * time. There is no special handling required except ignoring >>> + * the SIR register value just read and retrying. >>> + * See section 6.2.5 of AM335x TRM Literature Number: SPRUH73K >>> + * >>> + * Many a times, a spurious interrupt situation has been fixed >>> + * by adding a flush for the posted write acking the IRQ in >>> + * the device driver. Typically, this is going be the device >>> + * driver whose interrupt was handled just before the spurious >>> + * IRQ occurred. Pay attention to those device drivers if you >>> + * run into hitting the spurious IRQ condition below. >>> + */ >>> + if ((irqnr & SPURIOUSIRQ_MASK) == SPURIOUSIRQ_MASK) { >> >> sounds like unlikely() wouldn't hurt here. > > I can add, but looks like it does not make a big difference. See below. > >> >>> + pr_err_once("%s: spurious irq!\n", __func__); >>> + irq_err_count++; >>> + omap_ack_irq(NULL); >>> + return; >>> + } >>> + >>> irqnr &= ACTIVEIRQ_MASK; >>> - WARN_ONCE(!irqnr, "Spurious IRQ ?\n"); >>> handle_domain_irq(domain, irqnr, regs); >> >> care to run kernel function profiler against omap_intc_handle_irq() >> before and after this patch ? > > Before this patch I see average running time time of 34us. That > increases to 37.8us after this patch. With unlikely() the number I got > was 37.4us. So the benefit with unlikely() is in the noise range. > > This was using AM335x EVM at 720 MHz. Just sent a v3 with unlikely() and profiling information added to commit message. Thanks, Sekhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c index 8587d0f8d8c0..639708de5529 100644 --- a/drivers/irqchip/irq-omap-intc.c +++ b/drivers/irqchip/irq-omap-intc.c @@ -47,6 +47,7 @@ #define INTC_ILR0 0x0100 #define ACTIVEIRQ_MASK 0x7f /* omap2/3 active interrupt bits */ +#define SPURIOUSIRQ_MASK (0x1ffffff << 7) #define INTCPS_NR_ILR_REGS 128 #define INTCPS_NR_MIR_REGS 4 @@ -330,11 +331,35 @@ static int __init omap_init_irq(u32 base, struct device_node *node) static asmlinkage void __exception_irq_entry omap_intc_handle_irq(struct pt_regs *regs) { + extern unsigned long irq_err_count; u32 irqnr; irqnr = intc_readl(INTC_SIR); + + /* + * A spurious IRQ can result if interrupt that triggered the + * sorting is no longer active during the sorting (10 INTC + * functional clock cycles after interrupt assertion). Or a + * change in interrupt mask affected the result during sorting + * time. There is no special handling required except ignoring + * the SIR register value just read and retrying. + * See section 6.2.5 of AM335x TRM Literature Number: SPRUH73K + * + * Many a times, a spurious interrupt situation has been fixed + * by adding a flush for the posted write acking the IRQ in + * the device driver. Typically, this is going be the device + * driver whose interrupt was handled just before the spurious + * IRQ occurred. Pay attention to those device drivers if you + * run into hitting the spurious IRQ condition below. + */ + if ((irqnr & SPURIOUSIRQ_MASK) == SPURIOUSIRQ_MASK) { + pr_err_once("%s: spurious irq!\n", __func__); + irq_err_count++; + omap_ack_irq(NULL); + return; + } + irqnr &= ACTIVEIRQ_MASK; - WARN_ONCE(!irqnr, "Spurious IRQ ?\n"); handle_domain_irq(domain, irqnr, regs); }
Under some conditions, irq sorting procedure used by INTC can go wrong resulting in a spurious irq getting reported. If this condition is not handled, it results in endless stream of: unexpected IRQ trap at vector 00 messages from ack_bad_irq() Handle the spurious interrupt condition in omap-intc driver to prevent this. Signed-off-by: Sekhar Nori <nsekhar@ti.com> --- v2: increment error irq counter, use pr_err_once, add a comment on tips to debug spurious irq condition. This patch results in a checkpatch warning about extern definition of irq_err_count, but looks like thats the prevalent method of accessing that counter. drivers/irqchip/irq-omap-intc.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/