linux-kernel - Re: [PATCH 1/3] mfd: tps65090: Allow charger module to be used when no irq

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Date:	Wed, 16 Apr 2014 10:45:15 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Anton Vorontsov <anton@...msg.org>,
	Olof Johansson <olof@...om.net>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	AJAY KUMAR RAMAKRISHNA SHYMALAMMA <ajaykumar.rs@...sung.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mfd: tps65090: Allow charger module to be used when
 no irq

Lee,

On Wed, Apr 16, 2014 at 9:26 AM, Lee Jones <lee.jones@...aro.org> wrote:
>> >> On the ARM Chromebook tps65090 has two masters: the AP (the main
>> >> processor running linux) and the EC (the embedded controller).  The AP
>> >> is allowed to mess with FETs but the EC is in charge of charge control.
>> >>
>> >> The tps65090 interupt line is routed to both the AP and the EC, which
>> >> can cause quite a headache.  Having two people adjusting masks and
>> >> acking interrupts is a recipe for disaster.
>> >>
>> >> In the shipping kernel we had a hack to have the AP pay attention to
>> >> the IRQ but not to ack it.  It also wasn't supposed to configure the
>> >> IRQ in any way.  That hack allowed us to detect when the device was
>> >> charging without messing with the EC's state.
>> >>
>> >> The current tps65090 infrastructure makes the above difficult, and it
>> >> was a bit of a hack to begin with.  Rather than uglify the driver to
>> >> support it, just extend the driver's existing notion of "no irq" to
>> >> the charger.  This makes the charger code poll every 2 seconds for AC
>> >> detect, which is sufficient.
>> >>
>> >> Signed-off-by: Doug Anderson <dianders@...omium.org>
>> >> ---
>> >>  drivers/mfd/tps65090.c           | 14 ++++++--
>> >>  drivers/power/tps65090-charger.c | 76 +++++++++++++++++++++++++++++++---------
>> >>  2 files changed, 70 insertions(+), 20 deletions(-)
>> >
>> > For the MFD part:
>> >   Acked-by: Lee Jones <lee.jones@...aro.org>
>> >
>> > Anton,
>> >   If you are okay with this patch I'd be happy to create an immutable
>> > branch for you to pull from?
>> >
>> > Doug,
>> >   What is the relationship (dependencies) between this and the other
>> > patches in the set?
>>
>> This patch can be applied irrespective of other others in the series.
>
> What about the files in the patch? Could you make two separate patches
> from this one patch and it would still compile okay? I'm _guessing_
> the answer is yes?

Yes, they'll compile and even boot on their own.  I just tested it.

If I put only the MFD part in, then at boot I see:
  tps65090-charger tps65090-charger: Unable to get charger irq = -6
...but otherwise the system functions.

If I put only the charger part in, then at boot:
  tps65090-charger tps65090-charger: Unable to register irq 1 err -22
  tps65090-charger: probe of tps65090-charger failed with error -22

...so you need both patches in order to make things function, but they
can be applied separately.  I'll assume it will make your life easier
if I split this into two patches so I'll do that.

-Doug
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