linux-kernel - Re: [PATCH V2 3/4] ARM64 LPC: support serial based on low-pin-count

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Message-ID: <13406676.rztgqQLiFa@wuerfel>
Date:   Wed, 14 Sep 2016 14:07:22 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     "zhichang.yuan" <yuanzhichang@...ilicon.com>,
        zhichang <zhichang.yuan02@...il.com>, lorenzo.pieralisi@....com,
        gabriele.paoloni@...wei.com, minyard@....org,
        benh@...nel.crashing.org, john.garry@...wei.com,
        liviu.dudau@....com, linuxarm@...wei.com,
        linux-kernel@...r.kernel.org, zourongrong@...il.com
Subject: Re: [PATCH V2 3/4] ARM64 LPC: support serial based on low-pin-count

On Wednesday, September 14, 2016 7:48:49 PM CEST zhichang.yuan wrote:
> On 2016/9/8 17:58, Arnd Bergmann wrote:
> > On Thursday, September 8, 2016 5:51:25 PM CEST zhichang wrote:
> >> On 2016年09月07日 22:50, Arnd Bergmann wrote:
> >>> On Wednesday, September 7, 2016 9:33:52 PM CEST Zhichang Yuan wrote:
> >>>> From: "zhichang.yuan" <yuanzhichang@...ilicon.com>
> >>>>
> >>>> On Hip06 platform, a 16550 compatible UART is connected to low-pin-count and
> >>>> controlled through the LPC I/O cycles. This patch drives the UART port with
> >>>> the specific serial in/out function pair based on the indirect-IO mechanism
> >>>> introduced by Hip06 LPC driver.
> >>>>
> >>>> Signed-off-by: zhichang.yuan <yuanzhichang@...ilicon.com>
> >>>
> >>> Any reason this cannot just use the regular drivers/tty/serial/8250/8250_of.c
> >>> driver?
> >> I think two reasons for that:
> >> 1. 8250_of.c is only for devicetree, but we need to support ACPI device too;
> > 
> > ACPI has its own way of describing serial ports, use that instead.
> Could you give me some info about ACPI serial ports?
> I found there is _CRS specific for serial, but it seems no serial driver use that.

drivers/tty/serial/8250/8250_dw.c is a driver that uses ACPI matching,
and possibly drivers/tty/serial/8250/8250_pnp.c could work as well.

	Arnd