linux-kernel - Re: [RFC PATCH 0/2] serial: 8250_dw: IO space + polling mode support

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Date:   Mon, 26 Feb 2018 14:21:09 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     John Garry <john.garry@...wei.com>, gregkh@...uxfoundation.org,
        jslaby@...e.com, p.zabel@...gutronix.de, heiko@...ech.de,
        ed.blake@...drel.com, jhogan@...nel.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [RFC PATCH 0/2] serial: 8250_dw: IO space + polling mode support

On Mon, 2018-02-26 at 11:56 +0000, John Garry wrote:
> > > > > > Why you can't do properly in ACPI?
> > > > 
> > > > No answer here either.
> > > > 
> > > > Sorry, but with this level of communication it's no go for the
> > > > series.
> > > > 
> > > 
> > > Sorry if my answers did not tell you want you want to know.
> > > 
> > > My point was that the 8250_pnp driver would be used for a
> > > pnp_device,
> > > but we are creating a platform device for this UART slave so would
> > > require a platform device driver, that which 8250_dw.c is. But I
> > > will
> > > check on pnp device support.
> 
> Hi Andy,
> 
> > Perhaps it's not visible, though below is a description of the
> > drivers
> > we have:
> > 
> > 8250_dw - OF/ACPI driver for Synopsys DW (+ DW DMA)
> > 8250_lpss - PCI driver for Synopsys DW (+ DW DMA)
> > 8250_of -  generic 8250 compatible driver for OF
> > 8250_pci - generic 8250 compatible driver for PCI
> > 8250_pnp - generic 8250 compatible driver for ACPI
> > 
> > 8250_* (except core parts) - custom glue drivers per some IPs
> > 
> > By description you gave your driver fits 8250_pnp if ACPI tables
> > crafted
> > properly.
> > 
> > Share the ACPI excerpt and we can discuss further how to improve
> > them.
> > 
> 
> For a bit of background, MFD support was discussed here initially:
> https://lkml.org/lkml/2017/6/13/796
> 
> Here is the ACPI table:
> Scope(_SB) {
>    Device (LPC0) {
>      Name (_HID, "HISI0191")  // HiSi LPC
>      Name (_CRS, ResourceTemplate () {
>        Memory32Fixed (ReadWrite, 0xa01b0000, 0x1000)
>      })
>    }
> 
>    Device (LPC0.CON0) {
>      Name (_HID, "HISI1031")
>      // Name (_CID, "PNP0501") // cannot support PNP
>      Name (LORS, ResourceTemplate() {
>        QWordIO (
>          ResourceConsumer,
>      MinNotFixed,     // _MIF
>      MaxNotFixed,     // _MAF
>      PosDecode,
>      EntireRange,
>      0x0,             // _GRA
>      0x2F8,           // _MIN

>      0x3fff,          // _MAX

Shouldn't be 0x2ff ?

>      0x0,             // _TRA
>      0x08,            // _LEN
>      , ,
>      IO02
> 
> 
> The latest framework changes and host driver patchset are here:
> https://lkml.org/lkml/2018/2/19/465
> 

It still doesn't explain impediments you have.

Just few approaches comes to my mind:
 - move UART outside of parent device
 - register PNP driver manually for that cell instead of MFD
 - use serial8250 platform driver (I totally forgot that we have a
generic platform driver, so, it might be what you need to use at the
end)

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy