Re: [PATCH] serial: 8250: Add support for using platform_device resources

From: Esben Haabendal
Date: Tue May 07 2019 - 07:33:37 EST

Lee Jones <lee.jones@xxxxxxxxxx> writes:

> On Tue, 07 May 2019, Lee Jones wrote:
>> On Thu, 02 May 2019, Esben Haabendal wrote:
>> > Could you help clarify whether or not this patch is trying to do
>> > something odd/wrong?
>> >
>> > I might be misunderstanding Andy (probably is), but the discussion
>> > revolves around the changes I propose where I change the serial8250
>> > driver to use platform_get_resource() in favour of
>> > request_mem_region()/release_mem_region().
>> Since 'serial8250' is registered as a platform device, I don't see any
>> reason why it shouldn't have the capability to obtain its memory
>> regions from the platform_get_*() helpers.
> Not sure which device you're trying to enable, but if it's booted
> using Device Tree, you could always use 'of_serial'.

It is an x86_64 platform, so there is unfortunately no device tree.

> It does seem a little odd that the 'serial8250' IP block has been
> incorporated into an MFD. Which device is it you're trying to enable
> exactly?

It is a Xilinx FPGA, containing a number of different devices, including
5 16550A UART devices (XPS 16550 UART v3.00a). It also contains 3
Ethernet interfaces and a number of custom IP blocks.

The FPGA is connected to the CPU using PCIe, with all devices using
parts of a big common io memory block, specified by a PCI BAR.