linux-kernel - [v2] wdat_wdt: Problem with WDAT using shared registers

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Date:   Wed, 11 Oct 2023 16:47:42 +0800
From:   "xingtong.wu" <xingtong_wu@....com>
To:     linux-watchdog@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "Wu, Xing Tong" <XingTong.Wu@...mens.com>, jan.kiszka@...mens.com,
        tobias.schaffner@...mens.com, cedric.hombourger@...mens.com,
        gerd.haeussler.ext@...mens.com
Subject: [v2] wdat_wdt: Problem with WDAT using shared registers

change since v1:
 The time of the last email was wrong, correct the time in v2.

Hi

I want to use the wdat_wdt to support a watchdog of SIONCT (a multi-function device
(mfd)), and I register instructions for wdat_wdt in BIOS, it need registers 0x2e-0x2f
to access the watchdog, then register 0x2e-0x2f will be forever occupied by platform
device wdat_wdt, see the code: https://elixir.bootlin.com/linux/v6.6-rc5/source/drivers/acpi/acpi_watchdog.c#L180

but the 0x2e-0x2f are special, they are used for a multi-function device --SIONCT, the
device have many pins can not only support features for watchdog, but also other
features like leds, fans, temperature monitor... there are drivers for these pins, e.g.
gpio-f7188x, nct6775, w83627hf... these driver use the shared register 0x2e-0x2f. 

So the issue happened, the wdat_wdt occupied the shared register 0x2e-0x2f, then
the other driver can not load.

Here is the msg I collected from my device:

root@...-SIMATIC-IPC-BX-21A:/home/ipc# cat /proc/ioports 
0000-0cf7 : PCI Bus 0000:00
  0000-001f : dma1
  0020-0021 : pic1
  002e-002e : wdat_wdt
  002f-002f : wdat_wdt

It will cause other SIONCT drivers can not load, e.g.
root@...-SIMATIC-IPC-BX-21A:/home/ipc# modprobe gpio-f7188x
modprobe: ERROR: could not insert 'gpio_f7188x': No such device

And dmesg info is:
[  213.559168] gpio-f7188xI/O address 0x002e already in use

Same reason for other drivers:
root@...-SIMATIC-IPC-BX-21A:/home/ipc# modprobe nct6775
modprobe: ERROR: could not insert 'nct6775': No such device

Do you have any idea for the wdat_wdt to add support for multi-function device?

BRS
Xing Tong Wu