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

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Date:   Thu, 25 Jan 2018 15:45:39 +0000
From:   Lina Iyer <ilina@...eaurora.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     tglx@...utronix.de, jason@...edaemon.net, marc.zyngier@....com,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        sboyd@...eaurora.org, rnayak@...eaurora.org,
        asathyak@...eaurora.org
Subject: Re: [PATCH RFC 3/4] drivers: irqchip: pdc: log PDC info in FTRACE

On Tue, Jan 23 2018 at 18:13 +0000, Steven Rostedt wrote:
>On Tue, 23 Jan 2018 10:56:55 -0700
>Lina Iyer <ilina@...eaurora.org> wrote:
>
>> From: Archana Sathyakumar <asathyak@...eaurora.org>
>
>Hi Lina and Archana,
>
>>
>> Log key PDC pin configuration in FTRACE.
>>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Signed-off-by: Archana Sathyakumar <asathyak@...eaurora.org>
>> Signed-off-by: Lina Iyer <ilina@...eaurora.org>
>> ---
>>  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>
>