On 28/09/2024 14:33, Ian Dannapel wrote:

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+
+  spi-cpha: true
+
+  spi-cpol: true
+
+  spi-max-frequency:
+    maximum: 25000000
+
+  reg:
+    maxItems: 1
+
+  creset-gpios:

reset-gpios

Do not invent own properties.

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+    description:
+      reset and re-configuration trigger pin (low active)
+    maxItems: 1
+
+  cs-gpios:
+    description:
+      chip-select pin (low active)

Eee? That's a property of controller, not child. Aren't you duplicating
existing controller property?

This device uses this pin in combination with the reset to enter the
programming mode. Also, the driver must guarantee that the pin is

Isn't this the same on every SPI device?

Yes, but I was not very clear. In this case the pin must be hold
active including entering the programming mode. And if the controller

Just like every CS, no?

The only difference is that you must send entire programming sequence
without releasing the CS.

transfers the data in bursts, the pin is also not allowed to go
inactive between transfer bursts.

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active for the whole transfer process, including ending dummy bits.
This is why I added a warning to NOT use this driver with other
devices on the same bus.

Not really related. None of this grants exception from duplicating
controller's property.

How do you think it will even work in Linux, if same GPIO is requested
twice (imagine controller also has it)? Till now, this would be -EBUSY.

I expected that the controller is not able request the same gpio. From
the controller point of view, it is a device that does not have a chip
select. Not sure if the controller would be able to get to this gpio
if it is not explicitly given.

But it could be given. Don't think only about your case.

Your description earlier clearly suggests it is CS. Description here
suggests it is not a CS.

No clue then.

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But regardless of implementation, I still do not understand why do you
need duplicate same chip-select. Maybe just the naming is the confusion,
dunno.

This could be an option to make the difference to a "real chip-select"
clear, but it would drift away from the datasheet naming. Eg,
prog-select?

Please go back to datasheet. Which pin is this? CS, yes or not? If not,
then which other pin is CS?

Best regards,
Krzysztof