Re: [PATCH 1/3][v6] gpiolib: allow simultaneous setting of multiple GPIO outputs

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, Nov 4, 2014 at 5:12 PM, Rojhalat Ibrahim <imr@xxxxxxxxxxx> wrote:

> Introduce new functions gpiod_set_array & gpiod_set_raw_array to the consumer
> interface which allow setting multiple outputs with just one function call.
> Also add an optional set_multiple function to the driver interface. Without an
> implementation of that function in the chip driver outputs are set
> sequentially.
>
> Implementing the set_multiple function in a chip driver allows for:
> - Improved performance for certain use cases. The original motivation for this
>   was the task of configuring an FPGA. In that specific case, where 9 GPIO
>   lines have to be set many times, configuration time goes down from 48 s to
>   20 s when using the new function.
> - Simultaneous glitch-free setting of multiple pins on any kind of parallel
>   bus attached to GPIOs provided they all reside on the same chip and bank.
>
> Limitations:
>   Performance is only improved for normal high-low outputs. Open drain and
>   open source outputs are always set separately from each other. Those kinds
>   of outputs could probably be accelerated in a similar way if we could
>   forgo the error checking when setting GPIO directions.
>
> Signed-off-by: Rojhalat Ibrahim <imr@xxxxxxxxxxx>
> Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> Reviewed-by: Mark Brown <broonie@xxxxxxxxxx>

OK let's do this.

Patch applied!

Yours,
Linus Walleij
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