Re: [PATCH v2 1/2] clocksource: Add Oxford Semiconductor RPS Dual Timer

[Daniel Lezcano]

On 06/14/2016 11:52 AM, Neil Armstrong wrote:
> Hi Daniel,

Hi Neil,

[ ... ]

> > > +config OXNAS_RPS_TIMER
> >
> >     config OXNAS_RPS_TIMER "bla bla" if COMPILE_TEST
> OK
>
> Shoud I also add CLKSRC_OF ?

Yes, right.

> > > +	bool
> > > +	select CLKSRC_MMIO
> > > +	help
> > > +	  This enables support for the Oxford Semiconductor OXNAS RPS timers.
> > > +
> > > @@ -0,0 +1,270 @@
> > > +/*
> > > + * drivers/clocksource/timer-oxnas-rps.c
> > > + *
> > > + * Copyright (C) 2009 Oxford Semiconductor Ltd
> > > + * Copyright (C) 2013 Ma Haijun <mahaijuns@xxxxxxxxx>
> >
> > What are these two copyrights ?
> >
> > [ ... ]
>
> This driver is based from a driver from the OX820 sdk from Oxford and modified by Ma Haijun, thus the copyrights.

Ok.

> > > +static void __init oxnas_rps_timer_init(struct device_node *np)
> > > +{
> > > +	struct oxnas_rps_timer *rps;
> > > +	void __iomem *base;
> > > +	int ret;
> > > +
> > > +	rps = kzalloc(sizeof(*rps), GFP_KERNEL);
> > > +	if (WARN_ON(!rps))
> >
> > It is pointless to add a WARN_ON, kzalloc already does that on failure.
> >
> > > +		return;
> > > +
> > > +	rps->clk = of_clk_get(np, 0);
> > > +	if (WARN_ON(IS_ERR(rps->clk)))
> > > +		return;
>
> [....]
>
> > > +		goto err;
> > > +
> > > +	oxnas_rps_clockevent_init(rps);
> > > +	oxnas_rps_clocksource_init(rps);
> > > +
> > > +	return;
> >
> > err_iounmap:
> > 	iounmap(base);
> >
> > err_clk_unprepare:
> > 	clk_unprepare(rps->clk)
> >
> > err_clk_put:
> > > +	clk_put(rps->clk);
> > > +	kfree(rps);
> > > +}
> >
> > Regarding the current work I am doing to change the init function to return
> > an error in case of failure, can you do proper error handling in this
> > function and rollback ?
> >
> > 1. replace WARN_ON by a pr_err
> > 2. make oxnas_rps_clockevent_init and oxnas_rps_clocksource_init to return
> > an error code
> It can be done.
>
> > 3. rollback clockevent or clocksource if one fails.
> Sure, but as for 4.6, it seems neither sched_clock_register, clocksource_mmio_init or clockevents_config_and_register can be reverted !
> What should I do ?

Just try to do the best effort.

eg.

ret = oxnas_rps_clockevent_init(rps);
if (ret)
	goto err_...

ret = oxnas_rps_clocksource_init(rps);
if (ret)
	goto err_...

If the function themselves just return 0, it is fine for me.

I initiated a process to cleanup and factor out the clocksource / 
clockevents, so any changes being able to rollback will help in this 
process.

  -- Daniel



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