Re: [PATCH RFC 3/4] drivers: irqchip: pdc: log PDC info in FTRACE

[Lina Iyer]

On Tue, Jan 23 2018 at 18:13 +0000, Steven Rostedt wrote:
> On Tue, 23 Jan 2018 10:56:55 -0700
> Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote:
>
> > From: Archana Sathyakumar <asathyak@xxxxxxxxxxxxxx>
>
> Hi Lina and Archana,
>
> > Log key PDC pin configuration in FTRACE.
> >
> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> > Signed-off-by: Archana Sathyakumar <asathyak@xxxxxxxxxxxxxx>
> > Signed-off-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>
> > ---
> >  drivers/irqchip/qcom-pdc.c |  6 ++++++
> >  include/trace/events/pdc.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 56 insertions(+)
> >  create mode 100644 include/trace/events/pdc.h
> >
> > diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
> > index 57f1348bd81c..9b626e9f3a29 100644
> > --- a/drivers/irqchip/qcom-pdc.c
> > +++ b/drivers/irqchip/qcom-pdc.c
> > @@ -26,6 +26,8 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/slab.h>
> >  #include <linux/types.h>
> > +#define CREATE_TRACE_POINTS
> > +#include "trace/events/pdc.h"
> >
> >  #include "qcom-pdc.h"
> >
> > @@ -78,6 +80,7 @@ static inline void pdc_enable_intr(struct irq_data *d, bool on)
> >  			break;
> >  		udelay(5);
> >  	} while (1);
> > +	trace_irq_pin_config("enable", (u32)pin_out, (u32)d->hwirq, 0, on);
>
> I'm concerned with that string you are passing in.
>
> >  	spin_unlock_irqrestore(&pdc_lock, flags);
> >  	WARN_ON(r_enable != enable);
> >  }
> > @@ -161,6 +164,9 @@ static int qcom_pdc_gic_set_type(struct irq_data *d, unsigned int type)
> >  		udelay(5);
> >  	} while (1);
> >
> > +	trace_irq_pin_config("type_config", (u32)pin_out, (u32)d->hwirq,
>
> This one too.
>
> > +				pdc_type, 0);
> > +
> >  	/*
> >  	 * If type is edge triggered, forward that as Rising edge as PDC
> >  	 * takes care of converting falling edge to rising edge signal
> > diff --git a/include/trace/events/pdc.h b/include/trace/events/pdc.h
> > new file mode 100644
> > index 000000000000..bec54c414880
> > --- /dev/null
> > +++ b/include/trace/events/pdc.h
> > @@ -0,0 +1,50 @@
> > +/* Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 and
> > + * only version 2 as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#undef TRACE_SYSTEM
> > +#define TRACE_SYSTEM pdc
> > +
> > +#if !defined(_TRACE_PDC_) || defined(TRACE_HEADER_MULTI_READ)
> > +#define _TRACE_PDC_H_
> > +
> > +#include <linux/tracepoint.h>
> > +
> > +TRACE_EVENT(irq_pin_config,
> > +
> > +	TP_PROTO(char *func, u32 pin, u32 hwirq, u32 type, u32 enable),
> > +
> > +	TP_ARGS(func, pin, hwirq, type, enable),
> > +
> > +	TP_STRUCT__entry(
> > +		__field(char *, func)
> > +		__field(u32, pin)
> > +		__field(u32, hwirq)
> > +		__field(u32, type)
> > +		__field(u32, enable)
> > +	),
> > +
> > +	TP_fast_assign(
> > +		__entry->pin = pin;
> > +		__entry->func = func;
> > +		__entry->hwirq = hwirq;
> > +		__entry->type = type;
> > +		__entry->enable = enable;
> > +	),
> > +
> > +	TP_printk("%s hwirq:%u pin:%u type:%u enable:%u",
>
> %s is dereferencing a pointer, which works fine when reading the ASCII
> translated trace files (/sys/kernel/debug/tracing/trace and friends).
> But it breaks when we use trace-cmd or perf. Because they record the
> binary data and they do not have access to memory inside the kernel.
>
> What I would recommend is in pdc.h have:
>
> #define PDC_ENTRY		1
> #define PDC_TYPE_CONFIG		2
>
> Then have the tracepoints do instead of:
>
> 	trace_irq_pin_config("enable", ...);
> 	trace_irq_pin_config("type_config", ...);
>
> Have them do:
>
> 	trace_irq_pin_config(PDC_ENTRY, ...);
> 	trace_irq_pin_config(PDC_TYPE_CONFIG, ...);
>
> And then have:
>
> 	TP_PROTO(u32 func, ...)
>
> 	TP_STRUCT__entry(
> 		__field(u32, func)
> 		[...]
>
> 	TP_fast_assign(
> 		__entry->func = func;
> 		[...]
>
> 	TP_printk("%s hwirq...",
> 		print_symbolic(__entry->func,
> 				{ PDC_ENTRY, "entry" },
> 				{ PDC_TYPE_CONFIG, "type_config" }),
> 		[...]
>
> And you will get the same effect, with trace-cmd and perf still working
> as expected.
Thanks Steve. I will take care of it in the next spin.

-- Lina

> -- Steve
>
>
> > +		__entry->func, __entry->pin, __entry->hwirq, __entry->type,
> > +		__entry->enable)
> > +);
> > +
> > +#endif
> > +#define TRACE_INCLUDE_FILE pdc
> > +#include <trace/define_trace.h>