Messages in this thread | | | Subject | Re: [RFC PATCH 0/2] serial: 8250_dw: IO space + polling mode support | From | John Garry <> | Date | Mon, 26 Feb 2018 09:33:51 +0000 |
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On 23/02/2018 17:31, Andy Shevchenko wrote: > On Fri, 2018-02-23 at 11:02 +0000, John Garry wrote: >> On 23/02/2018 10:30, Andy Shevchenko wrote: >>> On Fri, 2018-02-23 at 02:42 +0800, John Garry wrote: >>>> There is a requirement >> >>> Where? >>
Hi Andy,
>> We require it for a development board for our hip06 platform. > > Okay, and this particular platform uses Synopsys IP?
As I see this uart is really a virtual 8250, so HW details like apb clocks and the like are hidden, so may not be relevant.
However I will check with the BMC team to know the specific details.
> >>>> for supporting an 8250-compatible UART with >>>> the following profile/features: >>>> - platform device >>>> - polling mode (i.e. no interrupt support) >>>> - ACPI FW >>> >>> Elaborate this one, please. >> >> So we need to define our own HID here, and cannot use PNP compatible >> CID >> (like PNP0501) as we cannot use the 8250 PNP driver. > > Why not? What are the impediments? >
To support the host controller for this device, we will create an MFD, i.e. platform device, per slave device.
>> This is related to the Hisi LPC ACPI support, where we would create >> an >> MFD (i.e. platform device) for the UART. > > Why you can't do properly in ACPI? > >>>> - IO port iotype >>>> - 16550-compatible >>>> >>>> For OF, we have 8250_of.c, and for PNP device we have 8250_pnp.c >>>> drivers. However there does not seem to any driver satisfying >>>> the above requirements. So this RFC is to find opinion on >>>> modifying the Synopsys DW 8250_dw.c driver to support these >>>> generic features. >>> >>> Synopsys 8250 is a particular case of platform drivers. It doesn't >>> satisfy "8250-compatible UART" requirement. > >> Right, but I wanted to try to use the generic parts of the driver to >> support this UART to save writing yet another driver. > > It's still odd. Why this one, why not 8250_foo_bar to touch instead? >
Agreed, it's odd. I choose as 8250_dw.c as it has ACPI support already. And I recognise the hw from popularity. No stronger reasons than that.
Thanks, John
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