linux-kernel - Re: [PATCH v3 09/11] serial: 8250_lpss: move Quark code from PCI driver

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Message-ID: <1462360835.17131.224.camel@linux.intel.com>
Date:	Wed, 04 May 2016 14:20:35 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>,
	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Vinod Koul <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dmaengine <dmaengine@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Puustinen, Ismo" <ismo.puustinen@...el.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v3 09/11] serial: 8250_lpss: move Quark code from PCI
 driver

On Wed, 2016-05-04 at 12:01 +0100, Bryan O'Donoghue wrote:
> On Wed, 2016-05-04 at 13:03 +0300, Andy Shevchenko wrote:
> > 
> > On Wed, May 4, 2016 at 12:51 PM, Bryan O'Donoghue
> > <pure.logic@...us-software.ie> wrote:
> > > 
> > > The default may be set to SERIAL_8250 but, without the QRK
> > > specific
> > > entry in 8250_pci.c you won't get console output.

That's, by the way, not true.

> > > 
> > > So if you are going to remove the QRK entry from 8250_pci.c and
> > > stuff
> > > it into 8250_lpss.c then 8250_lpss needs to be selected by
> > > CONFIG_SERIAL_8250_PCI.
> > Why?!
> > 
> > Now it should be enough to have SERIAL_8250 set to non-n to have
> > 8250_lpss compiled.
> > Can you check it?
> I'm sure that's true.
> 
> My point to you is that - its a highly non-intuitive thing to do on a
> reading of the datasheet for this part.
> 
> LPSS is, ostensibly at least, for passing processor resources via
> APCI.
> 
> If you look at a QRK datasheet it says "enumerate all this stuff via
> PCI" - there's not a single mention of LPSS. Its reasonable, correct
> and currently required for QRK to set CONFIG_8250_PCI.

User has no such item even visible until enable CONFIG_EXPERT.

Heikki sent an answer to you (and to the list, but by some reason it's
not yet there) an hour ago.

> 
> To move away from a valid/standard PCI probe routine into a new
> special
> LPSS/PCI shim (which the hardware doesn't actually mandate) I do think
> you should to setup the dependency CONFIG_8250_PCI =>
> CONFIG_8250_LPSS.

No, this is what we try avoiding, thus it will not happen.

If user selects CONFIG_SERIAL_8250_PCI, the CONFIG_SERIAL_8250_LPSS will
be selected as well since it has same dependencies.

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