[U-Boot] [PATCH] mx6: gpio: read data register if direction is out

[Fabio Estevam]

On Tue, Jun 24, 2014 at 10:07 AM, Stefano Babic <sbabic at denx.de> wrote:

> What you are describing looks an issue in your pinmux configuration
> because you do not set the SION bit, as requested to read back the value
> of the GPIO from the Pad Register.

Yes, correct.

Klaus, please check this commit:

commit 7773fd196918826ebaab769e63a4775607f5256c
Author: Otavio Salvador <otavio at ossystems.com.br>
Date:   Mon Dec 16 20:44:00 2013 -0200

    imx: Easy enabling of SION per-pin using MUX_MODE_SION helper macro

    The macro allows easy setting in per-pin, as for example:

    ,----
    | imx_iomux_v3_setup_pad(MX6_PAD_NANDF_D1__GPIO_2_1 | MUX_MODE_SION);
    `----

    The IOMUX_CONFIG_SION allows for reading PAD value from PSR register.

    The following quote from the datasheet:

    ,----
    | ...
    | 28.4.2.2 GPIO Write Mode
    | The programming sequence for driving output signals should be as follows:
    | 1. Configure IOMUX to select GPIO mode (Via IOMUXC), also enable
SION if need
    | to read loopback pad value through PSR
    | 2. Configure GPIO direction register to output (GPIO_GDIR[GDIR]
set to 1b).
    | 3. Write value to data register (GPIO_DR).
    | ...
    `----

    This fixes the gpio_get_value to properly work when a GPIO is set for
    output and has no conflicts.

    Thanks for Benoît Thébaudeau <benoit.thebaudeau at advansee.com>, Fabio
    Estevam <fabio.estevam at freescale.com> and Eric Bénard
    <eric at eukrea.com> for helping to properly trace this down.

    Signed-off-by: Otavio Salvador <otavio at ossystems.com.br>
    Acked-by: Stefano Babic <sbabic at denx.de>