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

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  Re: [PATCH V2 3/4] ARM64 LPC: support serial based on low-pin-count "zhichang.yuan" <yuanzhichang@hisilicon.com> - 2016-09-14 14:00 +0200
    Re: [PATCH V2 3/4] ARM64 LPC: support serial based on low-pin-count Arnd Bergmann <arnd@arndb.de> - 2016-09-14 14:10 +0200

#1483218 — Re: [PATCH V2 3/4] ARM64 LPC: support serial based on low-pin-count

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@hisilicon.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@hisilicon.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.

Thanks!
Zhichang

> 
>> 2. It seems UPIO_PORT is not supported there.
> 
> Should be easy enough to add.
> 
> 	Arnd
> 
> .
> 

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#1483230

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@hisilicon.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@hisilicon.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

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