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 <ste...@herbrechtsmeier.net>
Signed-off-by: Michal Simek <michal.si...@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
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