Re: mt7621: gpio-hog not working properly

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Wed, Nov 13, 2019 at 9:54 PM René van Dorst <opensource@xxxxxxxxxx> wrote:

> mt7621 used bgpio_set_with_clear() because we have `set` and `clear`
> registers.
(...)
> It seems that writing to the 'clear' register doesn't do anything.
> I noticed that register address is 0x1e000000 in the DTS but in the
> code it is 0xbe000000.

Do you mean physical memory 0x1e000000 gets remapped
at virtual memory 0xbe000000?

> [    3.158002] bgpio_write32: 0xbe000600 <= 0x80
> [    3.165258] GPIO line 487 (sfp_i2c_clk_gate) hogged as output/high
> [    3.177532] gpiochip_add_data_with_key: gpiochip0 gpio7: 0x843
>
> When using program 'io' writing to the `clear` register 0x1e000640
> does have effect.
>
> root@OpenWrt:/# io -4 0x1e000620
> 1e000620:  0b75f7de
> root@OpenWrt:/# io -4 -w 0x1e000640 0x80
> root@OpenWrt:/# io -4 0x1e000620
> 1e000620:  0b75f74e
(...)
> If I change the bgpio_init() values so that we don't have the `set`
> and `clear` registers.
> With the patch below I do get right results.

That's weird!

> Any idea what this can be?

Try to pass the flag BGPIOF_UNREADABLE_REG_SET,
it seems the code is using the set register to read back the
value. In this case it is actually working you just don't see
it in debugfs.

Cc:ed Sergio maybe he has some ideas.

It seems to be hardware related then, hm.

Yours,
Linus Walleij