Am 24.07.2018 um 12:31 schrieb Michal Simek:
On 23.7.2018 20:42, Stefan Herbrechtsmeier wrote:
Am 23.07.2018 um 13:43 schrieb Michal Simek:
Reading registers for finding out output value is not working because input value is read instead in case of tristate.
Reported-by: Stefan Herbrechtsmeier stefan@herbrechtsmeier.net Signed-off-by: Michal Simek michal.simek@xilinx.com
drivers/gpio/xilinx_gpio.c | 38 +++++++++++++++++++++++++++++++++----- 1 file changed, 33 insertions(+), 5 deletions(-)
diff --git a/drivers/gpio/xilinx_gpio.c b/drivers/gpio/xilinx_gpio.c index 4da9ae114d87..9d3e9379d0e5 100644 --- a/drivers/gpio/xilinx_gpio.c +++ b/drivers/gpio/xilinx_gpio.c
[snip]
+ priv->output_val[bank] = val;
return val; }; @@ -441,6 +449,7 @@ static int xilinx_gpio_get_function(struct udevice *dev, unsigned offset) static int xilinx_gpio_get_value(struct udevice *dev, unsigned offset) { struct xilinx_gpio_platdata *platdata = dev_get_platdata(dev); + struct xilinx_gpio_privdata *priv = dev_get_priv(dev); int val, ret; u32 bank, pin; @@ -451,7 +460,14 @@ static int xilinx_gpio_get_value(struct udevice *dev, unsigned offset) debug("%s: regs: %lx, gpio: %x, bank %x, pin %x\n", __func__, (ulong)platdata->regs, offset, bank, pin); - val = readl(&platdata->regs->gpiodata + bank * 2); + if (xilinx_gpio_get_function(dev, offset) == GPIOF_INPUT) { + debug("%s: Read input value from reg\n", __func__); + val = readl(&platdata->regs->gpiodata + bank * 2); + } else { + debug("%s: Read saved output value\n", __func__); + val = priv->output_val[bank]; + }
Why you don't always read the data register? This doesn't work for three state outputs.
In three state register every bit/pin is 0 - output, 1 input. It means else part is output and I read saved value in priv->output_val. If pin is setup as INPUT then I need read data reg to find out input value. Maybe you are commenting something else but please let me know if there is any other bug.
What happen if I have an open drain output. Even if the gpio output is 1 the input could read a 0. You driver will always return the output value and not the real input value. According to the picture in documentation and my tests a data register write writes the output registers and a data register read reads the input registers.
Why should the driver return the desired state (output register) and not the real state (input register)?
Best regards Stefan