Am 2023-04-24 17:39, schrieb Sahin, Okan:
Am 2023-04-09 16:25, schrieb Sahin, Okan:
Fri, Apr 07, 2023 at 03:48:25PM +0200, Linus Walleij kirjoitti:
On Wed, Apr 5, 2023 at 3:57 PM Michael Walle <michael@xxxxxxxx>
wrote:
> OTOH I'm not sure the driver is doing it correctly, because it also
> seems to switch the pullup resisters together with the direction.
> I'm not sure that is correct. So there might be just one register
> involved after all and the GPIO_REGMAP should work again.
I'm pretty sure that should be in the .set_config() callback.
> Also, according to the datasheet this has some nv memory (to set the
> initial state of the GPIOs [?]). So it should really be a
> multi-function device. I'm not sure if this has to be considered
> right from the beginning or if the device support can start with
> GPIO only and later be transitioned to a full featured MFD (probably with
nvmem
support).
That's a bit of a soft definition.
If the chip is *only* doing GPIO and nvram it can be a GPIO-only
device I think.
The precedent is a ton of ethernet drivers with nvram for storing
e.g.
the MAC address. We don't make all of those into MFDs, as the nvram
is
closely tied to the one and only function of the block.
I agree with Linus. This should be part of the actual (main) driver
for the chip as many
do (like USB to serial adapters that have GPIO capability).
You mean the gpio driver is calling nvmem_register()? Yeah I agree,
that
should work.
I think gpio_regmap is not suitable for this driver as Michael
stated.
https://www.analog.com/media/en/technical-documentation/data-
sheets/ds4520.pdf
Please check block diagram. There are two input registers that
control
gpio state
so gpio_regmap does not look ok for this. Am I missing something?
You mean F8/F9? That will work as they are for different GPIOs. What
doesn't work with gpio-regmap is when you need to modify two different
registers for one GPIO. Have a look at gpio_regmap_get() and
gpio_regmap_set(). If the default gpio_regmap_simple_xlate() doesn't
work
you can use your own .xlate() op.
Actually, I checked the functions that you suggested, but as far as I
understand
they might work if there would be one bit to set direction or value.
However,
this is not the case for ds4520. In other words, if I want to set the
gpio direction
as output, I need to set a corresponding bit for both F0 and F1
registers.
I can't follow. F0/F1 is for the pull-up. That was actually my initial
question and Linus said, that should probably be done in a seperate
.set_config operation not together with a direction change.
In the document, you can see block diagram. I do not know why, but
design is
not standard that’s why I think I can not use gpio-regmap.
Also, at this point I am not planning to add nvmem support.
That is a pity, because that is the whole use case for this gpio
expander,
no? "Programmable Replacement for Mechanical Jumpers and Switches"
I can set "SEE" bit as "0" in the Configuration Register to write
EEPROM so it might solve
issue.
If you do that unconditionally, that might wear out the EEPROM,
though.
-michael
