Re: [PATCH RFC v2 3/3] drivers: irqchip: pdc: log PDC info in FTRACE

[Steven Rostedt]

On Fri,  2 Feb 2018 07:22:00 -0700
Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote:

Hi Lina,

This looks really good. I have one nit below.


> From: Archana Sathyakumar <asathyak@xxxxxxxxxxxxxx>
> 
> 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 |  7 ++++++
>  include/trace/events/pdc.h | 55 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 62 insertions(+)
>  create mode 100644 include/trace/events/pdc.h
> 
> diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
> index a392380eada6..7f177ad88713 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"
>  
>  #define PDC_MAX_IRQS		126
>  
> @@ -68,6 +70,8 @@ static inline void pdc_enable_intr(struct irq_data *d, bool on)
>  	enable = on ? ENABLE_INTR(enable, mask) : CLEAR_INTR(enable, mask);
>  	pdc_reg_write(IRQ_ENABLE_BANK, index, enable);
>  	spin_unlock_irqrestore(&pdc_lock, flags);
> +
> +	trace_irq_pin_config(PDC_ENTRY, pin_out, (u64)d->chip_data, 0, on);
>  }
>  
>  static void qcom_pdc_gic_mask(struct irq_data *d)
> @@ -149,6 +153,9 @@ static int qcom_pdc_gic_set_type(struct irq_data *d, unsigned int type)
>  
>  	pdc_reg_write(IRQ_i_CFG, pin_out, pdc_type);
>  
> +	trace_irq_pin_config(PDC_TYPE_CONFIG, pin_out, (u64)d->chip_data,
> +				pdc_type, 0);

I wonder if it makes more sense to just pass 'd' into the trace events,
and then do the dereference there. The reason is to try to get as much
code out of the calling path as possible. Even though trace events use
jump labels and have no conditional branches, the code to call the
function is still within the code using the trace events. By passing in
'd' and doing the redirect in the trace event code, we remove the
setting up of the redirect from the caller, and save some cache lines
in the process.

-- Steve



> +
>  	return irq_chip_set_type_parent(d, type);
>  }
>  
> diff --git a/include/trace/events/pdc.h b/include/trace/events/pdc.h
> new file mode 100644
> index 000000000000..0e894bbc9e85
> --- /dev/null
> +++ b/include/trace/events/pdc.h
> @@ -0,0 +1,55 @@
> +/* 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>
> +
> +#define PDC_ENTRY		1
> +#define PDC_TYPE_CONFIG		2
> +
> +TRACE_EVENT(irq_pin_config,
> +
> +	TP_PROTO(u32 func, int pin, u64 hwirq, u32 type, u32 enable),
> +
> +	TP_ARGS(func, pin, hwirq, type, enable),
> +
> +	TP_STRUCT__entry(
> +		__field(u32, func)
> +		__field(int, pin)
> +		__field(u64, hwirq)
> +		__field(u32, type)
> +		__field(u32, enable)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->func = func;
> +		__entry->pin = pin;
> +		__entry->hwirq = hwirq;
> +		__entry->type = type;
> +		__entry->enable = enable;
> +	),
> +
> +	TP_printk("%s hwirq:%lu pin:%d type:%u enable:%u",
> +		print_symbolic(__entry->func,
> +				{ PDC_ENTRY, "pdc_entry" },
> +				{ PDC_TYPE_CONFIG, "pdc_type_config" }),
> +		__entry->pin, __entry->hwirq, __entry->type, __entry->enable)
> +);
> +
> +#endif
> +#define TRACE_INCLUDE_FILE pdc
> +#include <trace/define_trace.h>