netdev - Re: [PATCH] ptp: ocp: don't allow on S390

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Message-ID: <0e6bd492-a3f5-845c-9d93-50f1cc182a62@infradead.org>
Date:   Thu, 19 Aug 2021 15:58:32 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jonathan Lemon <jonathan.lemon@...il.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
Cc:     netdev@...r.kernel.org, Richard Cochran <richardcochran@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] ptp: ocp: don't allow on S390

On 8/16/21 2:41 PM, Jonathan Lemon wrote:
> On Mon, Aug 16, 2021 at 02:15:51PM -0700, Randy Dunlap wrote:
>> On 8/16/21 2:09 PM, Jonathan Lemon wrote:
>>> On Fri, Aug 13, 2021 at 01:30:26PM -0700, Randy Dunlap wrote:
>>>> There is no 8250 serial on S390. See commit 1598e38c0770.
>>>
>>> There's a 8250 serial device on the PCI card.   Its been
>>> ages since I've worked on the architecture, but does S390
>>> even support PCI?
>>
>> Yes, it does.
>>
>>>> Is this driver useful even without 8250 serial?
>>>
>>> The FB timecard has an FPGA that will internally parse the
>>> GNSS strings and correct the clock, so the PTP clock will
>>> work even without the serial devices.
>>>
>>> However, there are userspace tools which want to read the
>>> GNSS signal (for holdolver and leap second indication),
>>> which is why they are exposed.
>>
>> So what do you recommend here?
> 
> Looking at 1598e38c0770, it appears the 8250 console is the
> problem.  Couldn't S390 be fenced by SERIAL_8250_CONSOLE, instead
> of SERIAL_8250, which would make the 8250 driver available?

OK, that sounds somewhat reasonable.

> For now, just disabling the driver on S390 sounds reasonable.
> 

S390 people, how does this look to you?

This still avoids having serial 8250 console conflicting
with S390's sclp console.
(reference commit 1598e38c0770)


---
  drivers/tty/serial/8250/Kconfig |    2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20210819.orig/drivers/tty/serial/8250/Kconfig
+++ linux-next-20210819/drivers/tty/serial/8250/Kconfig
@@ -6,7 +6,6 @@
  
  config SERIAL_8250
  	tristate "8250/16550 and compatible serial support"
-	depends on !S390
  	select SERIAL_CORE
  	select SERIAL_MCTRL_GPIO if GPIOLIB
  	help
@@ -85,6 +84,7 @@ config SERIAL_8250_FINTEK
  config SERIAL_8250_CONSOLE
  	bool "Console on 8250/16550 and compatible serial port"
  	depends on SERIAL_8250=y
+	depends on !S390
  	select SERIAL_CORE_CONSOLE
  	select SERIAL_EARLYCON
  	help


-- 
~Randy