[PATCH v2 0/1] gpio: mpc8xxx: latch GPIOs state on module load when configured as output

[PATCH v2 0/1] gpio: mpc8xxx: latch GPIOs state on module load when configured as output

[msmulski2]

From: Michal Smulski <michal.smulski@ooma.com>

Changes between v1 and v2:
* moved comments closer to the added code for clarity.

Michal Smulski (1):
  gpio: mpc8xxx: latch GPIOs state on module load when configured as
    output

 drivers/gpio/gpio-mpc8xxx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.34.1

[PATCH v2 1/1] gpio: mpc8xxx: latch GPIOs state on module load when configured as output

[msmulski2]

From: Michal Smulski <michal.smulski@ooma.com>

Qoriq and related devices allow reading out state of GPIO set as output.
However, currently on driver's init, all outputs are configured as driven
low. So, any changes to GPIO confiuration will drive all pins (configured
as output) as output-low.
This patch latches state of output GPIOs before any GPIO configuration
takes place. This preserves any output settings done prior to loading
the driver (for example, by u-boot).

Signed-off-by: Michal Smulski <michal.smulski@ooma.com>
---
 drivers/gpio/gpio-mpc8xxx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-mpc8xxx.c b/drivers/gpio/gpio-mpc8xxx.c
index 3eb08cd1fdc0..6340e738c912 100644
--- a/drivers/gpio/gpio-mpc8xxx.c
+++ b/drivers/gpio/gpio-mpc8xxx.c
@@ -375,8 +375,12 @@ static int mpc8xxx_probe(struct platform_device *pdev)
 	if (of_device_is_compatible(np, "fsl,qoriq-gpio") ||
 	    of_device_is_compatible(np, "fsl,ls1028a-gpio") ||
 	    of_device_is_compatible(np, "fsl,ls1088a-gpio") ||
-	    is_acpi_node(fwnode))
+	    is_acpi_node(fwnode)) {
 		gc->write_reg(mpc8xxx_gc->regs + GPIO_IBE, 0xffffffff);
+		/* Also, latch state of GPIOs configured as output by bootloader. */
+		gc->bgpio_data = gc->read_reg(mpc8xxx_gc->regs + GPIO_DAT) &
+			gc->read_reg(mpc8xxx_gc->regs + GPIO_DIR);
+	}
 
 	ret = devm_gpiochip_add_data(&pdev->dev, gc, mpc8xxx_gc);
 	if (ret) {
-- 
2.34.1

Re: [PATCH v2 1/1] gpio: mpc8xxx: latch GPIOs state on module load when configured as output

[Bartosz Golaszewski]

On Fri, Jun 2, 2023 at 1:02 AM <msmulski2@gmail.com> wrote:
>
> From: Michal Smulski <michal.smulski@ooma.com>
>
> Qoriq and related devices allow reading out state of GPIO set as output.
> However, currently on driver's init, all outputs are configured as driven
> low. So, any changes to GPIO confiuration will drive all pins (configured
> as output) as output-low.
> This patch latches state of output GPIOs before any GPIO configuration
> takes place. This preserves any output settings done prior to loading
> the driver (for example, by u-boot).
>
> Signed-off-by: Michal Smulski <michal.smulski@ooma.com>
> ---
>  drivers/gpio/gpio-mpc8xxx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-mpc8xxx.c b/drivers/gpio/gpio-mpc8xxx.c
> index 3eb08cd1fdc0..6340e738c912 100644
> --- a/drivers/gpio/gpio-mpc8xxx.c
> +++ b/drivers/gpio/gpio-mpc8xxx.c
> @@ -375,8 +375,12 @@ static int mpc8xxx_probe(struct platform_device *pdev)
>         if (of_device_is_compatible(np, "fsl,qoriq-gpio") ||
>             of_device_is_compatible(np, "fsl,ls1028a-gpio") ||
>             of_device_is_compatible(np, "fsl,ls1088a-gpio") ||
> -           is_acpi_node(fwnode))
> +           is_acpi_node(fwnode)) {
>                 gc->write_reg(mpc8xxx_gc->regs + GPIO_IBE, 0xffffffff);
> +               /* Also, latch state of GPIOs configured as output by bootloader. */
> +               gc->bgpio_data = gc->read_reg(mpc8xxx_gc->regs + GPIO_DAT) &
> +                       gc->read_reg(mpc8xxx_gc->regs + GPIO_DIR);
> +       }
>
>         ret = devm_gpiochip_add_data(&pdev->dev, gc, mpc8xxx_gc);
>         if (ret) {
> --
> 2.34.1
>

Applied, thanks!

Bart