linux-kernel - Re: [PATCH] spmi-pmic-arb: add irq tracepoints to the pmic-arb driver

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Date:	Thu, 28 May 2015 17:02:50 -0600
From:	Gilad Avidov <gavidov@...eaurora.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Ankit Gupta <ankgupta@...eaurora.org>, sdharia@...eaurora.org,
	ivan.ivanov@...aro.org, svarbanov@...sol.com, rostedt@...dmis.org,
	linux-arm-msm@...r.kernel.org, gregkh@...uxfoundation.org,
	collinsd@...eaurora.org, osvaldob@...eaurora.org,
	linux-kernel@...r.kernel.org, mlocke@...eaurora.org,
	galak@...eaurora.org, agross@...eaurora.org
Subject: Re: [PATCH] spmi-pmic-arb: add irq tracepoints to the pmic-arb
 driver

On Wed, 27 May 2015 13:06:29 -0700
Stephen Boyd <sboyd@...eaurora.org> wrote:

> On 05/27, Ankit Gupta wrote:
> > >
> > > How is this any better than irq tracepoints that we already have
> > > for generic irqs?
> > >
> > It is better than generic irq tracepoints because it provides bus
> > specific information (sid and address(pid) of slave write), driver
> > specific information (apid (pmic-peripheral) and func_num) and
> > statistics (apid range).
> > Recall that *slave* read/write cannot be traced by the spmi
> > framework ftrace.
> > 
> 
> Don't we already get all this information based on how we map
> interrupts to devices in DT? It feels to me that the same
> argument here could be applied to all the random gpio expanders
> and chained interrupt controllers that we support in the kernel.
> 

We don't.
We could get the same information if we had the irq-domain and hw-irq
32bit value. While these values are available from /proc/interrupt,
they are not available from the irq event tracing.

This patch traces spmi slave-originated events. If we had one such
slave we could cross information from both sources to filter the trace
events. However, we have hundreds of transaction-capable spmi slaves.

Thanks,
Gilad

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