From: syin@broadcom•com (Sherman Yin)
To: linux-arm-kernel@lists•infradead.org
Subject: pinctrl: pinctrl-single vs custom driver
Date: Fri, 7 Mar 2014 16:49:40 -0800 [thread overview]
Message-ID: <531A6924.8080009@broadcom.com> (raw)
In-Reply-To: <CACRpkdYhCDpKxkMxcHHLyp2mTf8-3mhioZkNqQACHcKjL+3erQ@mail.gmail.com>
>> Like the bcm281xx, in this SoC, each pin is also controlled by 1 register,
>> so pinctrl-single should work.
>
> One other deciding factor is what kind of information you have available
> on these pin registers and what format they are in. If your system is
> well documented and not delivered in some register map description
> format you should typically open code the hardware information in the
> driver.
The info available is similar to the bcm281xx pinctrl driver - basically
just what is available in the binding documentation. Although that is
still not 100% clear, it is still much better than just numerical
register values.
>> Is this efficiency enough to warrant using pinctrl-single over a "normal"
>> pinctrl driver in this case?
>
> So I would say that this code execution is likely not on the time-critical
> path?
Pins are typically changed on suspend/resume to save power, so I don't
think it is time-critical. Also, I could cache the pin values (provided
we can assure that all software change pins via my driver) to save a few
messages should timing/messaging congestion become a concern. I won't
implement the cache unless we really run into timing problems without it.
> Also take the debuggability and understandability of the code as a
> very important factor. Which driver will be easiest for a developer to
> cope with, and which will be easiest to use when debugging the
> system?
Okay. The new driver will be similar to the bcm281xx one and will not
be based on pinctrl-single, so that code is a bit easier to understand
and the device tree nodes will be more readable.
Thanks for your input, Linus!
Regards,
Sherman
prev parent reply other threads:[~2014-03-08 0:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-25 2:24 pinctrl: pinctrl-single vs custom driver Sherman Yin
2014-03-05 1:31 ` Linus Walleij
2014-03-08 0:49 ` Sherman Yin [this message]
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