linux-kernel - Re: [PATCH] serial: 8250: Add support for using platform

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Date:   Tue, 7 May 2019 00:04:30 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Esben Haabendal <esben@...bendal.dk>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lee Jones <lee.jones@...aro.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Enrico Weigelt <lkml@...ux.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Darwin Dingel <darwin.dingel@...iedtelesis.co.nz>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        He Zhe <zhe.he@...driver.com>, Marek Vasut <marex@...x.de>,
        Douglas Anderson <dianders@...omium.org>,
        Paul Burton <paul.burton@...s.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250: Add support for using platform_device resources

Let's start from simple things:
- I really failed to find where resources are requested in
mfd_add_device():
https://elixir.bootlin.com/linux/latest/ident/mfd_add_device
- as for 8250_dw.c (as MFD child of intel-lpss-pci.c) see below...

1. 8250_dw.c remaps resources, but doesn't request them.
2. It calls
 -> serial8250_register_8250_port(), which sets UPF_BOOT_AUTOCONF
unconditionally, as you noticed
  -> uart_add_one_port()
   -> uart_configure_port()
    -> port->ops->config_port(), if UPF_BOOT_AUTOCONF is set, see above
3. And ->config_port() is defined to serial8250_config_port() in
https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/8250/8250_port.c#L3147

So, it *does* request resources implicitly via 8250 core.

I maybe miss something obvious, though.

-- 
With Best Regards,
Andy Shevchenko