[PATCH] ARM: dts: imx6q-bx50v3: configure unused pca953x pins

[Ken.Lin]

Hi,

1. As you can see in the datasheet(http://www.ti.com/lit/ds/scps202c/scps202c.pdf), at power on, P00 - P17 are configured as inputs (by chip default setting, datasheet P.3) and an interrupt is generated by any rising or falling edge of the port inputs in the input mode (datasheet P.10)

2. The unhandled interrupts ( return IRQ_NONE in pca953x_irq_handler) in GPIO expander driver (drivers/gpio/gpio-pca953x.c) could happen when unused GPIO pins in GPIO expander are not well configured.

3. As a result, we tried to configure the unused (default floating inputs) pca953x GPIO pins as GPO low to avoid the unexpected interrupts (could be observed during the interference situation e.g. putting fingers on the unused pin to make the signal level change)


Cheers,
ken Lin


-----Original Message-----
From: Uwe Kleine-König [mailto:u.kleine-koenig at pengutronix.de]
Sent: Monday, August 15, 2016 1:31 PM
To: Akshay Bhat
Cc: shawnguo at kernel.org; linux-arm-kernel at lists.infradead.org; kernel at pengutronix.de; Ken.Lin
Subject: Re: [PATCH] ARM: dts: imx6q-bx50v3: configure unused pca953x pins

Hello,

On Fri, Aug 12, 2016 at 01:45:11PM -0400, Akshay Bhat wrote:
> At power on, pca953x GPIO pins are configured as input and may cause 
> unexpected interrupts. Configure the unused pins as GPO low to avoid 
> unexpected interrupts.

Is this really about irqs? There should be no irqs for lines where no irq is requested. Can you describe the problem in more detail?

Bst regards
Uwe

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