* [PATCH] serial: forbid 8250 on s390
@ 2017-12-12 8:08 Christian Borntraeger
2017-12-12 8:48 ` Greg Kroah-Hartman
2017-12-12 15:50 ` Alan Cox
0 siblings, 2 replies; 5+ messages in thread
From: Christian Borntraeger @ 2017-12-12 8:08 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby
Cc: linux-serial, linux-s390, linux-kernel, Christian Borntraeger
Using "make kvmconfig" results in a potentially unusable linux image
on s390. The reason is that both the (default on s390) sclp consoles
as well as the 8250 console register a ttyS<x> as console. Since there
will be no 8250 on s390 let's fence 8250. This will ensure that there
is always a working sclp console.
Reported-by: Alice Frosi <alice@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
---
drivers/tty/serial/8250/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index a5c0ef1..16b1496 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -5,6 +5,7 @@
config SERIAL_8250
tristate "8250/16550 and compatible serial support"
+ depends on !S390
select SERIAL_CORE
---help---
This selects whether you want to include the driver for the standard
--
2.9.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] serial: forbid 8250 on s390
2017-12-12 8:08 [PATCH] serial: forbid 8250 on s390 Christian Borntraeger
@ 2017-12-12 8:48 ` Greg Kroah-Hartman
2017-12-12 8:56 ` Christian Borntraeger
2017-12-12 15:50 ` Alan Cox
1 sibling, 1 reply; 5+ messages in thread
From: Greg Kroah-Hartman @ 2017-12-12 8:48 UTC (permalink / raw)
To: Christian Borntraeger; +Cc: Jiri Slaby, linux-serial, linux-s390, linux-kernel
On Tue, Dec 12, 2017 at 09:08:35AM +0100, Christian Borntraeger wrote:
> Using "make kvmconfig" results in a potentially unusable linux image
> on s390. The reason is that both the (default on s390) sclp consoles
> as well as the 8250 console register a ttyS<x> as console. Since there
> will be no 8250 on s390 let's fence 8250. This will ensure that there
> is always a working sclp console.
>
> Reported-by: Alice Frosi <alice@linux.vnet.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
> ---
> drivers/tty/serial/8250/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
Does this need to be backported to any stable kernels? Or does anyone
who runs them on s390 already have this config option disabled?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] serial: forbid 8250 on s390
2017-12-12 8:48 ` Greg Kroah-Hartman
@ 2017-12-12 8:56 ` Christian Borntraeger
0 siblings, 0 replies; 5+ messages in thread
From: Christian Borntraeger @ 2017-12-12 8:56 UTC (permalink / raw)
To: Greg Kroah-Hartman; +Cc: Jiri Slaby, linux-serial, linux-s390, linux-kernel
On 12/12/2017 09:48 AM, Greg Kroah-Hartman wrote:
> On Tue, Dec 12, 2017 at 09:08:35AM +0100, Christian Borntraeger wrote:
>> Using "make kvmconfig" results in a potentially unusable linux image
>> on s390. The reason is that both the (default on s390) sclp consoles
>> as well as the 8250 console register a ttyS<x> as console. Since there
>> will be no 8250 on s390 let's fence 8250. This will ensure that there
>> is always a working sclp console.
>>
>> Reported-by: Alice Frosi <alice@linux.vnet.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
>> ---
>> drivers/tty/serial/8250/Kconfig | 1 +
>> 1 file changed, 1 insertion(+)
>
> Does this need to be backported to any stable kernels? Or does anyone
> who runs them on s390 already have this config option disabled?
All shipped s390 kernels have 8250 disabled anyway. A backport of this
patch could be helpful to let users who want to use "make kvmconfig" give
a working configuration but it is certainly not critical.
Christian
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] serial: forbid 8250 on s390
2017-12-12 8:08 [PATCH] serial: forbid 8250 on s390 Christian Borntraeger
2017-12-12 8:48 ` Greg Kroah-Hartman
@ 2017-12-12 15:50 ` Alan Cox
2017-12-12 17:50 ` Christian Borntraeger
1 sibling, 1 reply; 5+ messages in thread
From: Alan Cox @ 2017-12-12 15:50 UTC (permalink / raw)
To: Christian Borntraeger
Cc: Greg Kroah-Hartman, Jiri Slaby, linux-serial, linux-s390, linux-kernel
On Tue, 12 Dec 2017 09:08:35 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> Using "make kvmconfig" results in a potentially unusable linux image
> on s390. The reason is that both the (default on s390) sclp consoles
> as well as the 8250 console register a ttyS<x> as console. Since there
> will be no 8250 on s390 let's fence 8250. This will ensure that there
> is always a working sclp console.
And there is no physical way to attach a PCI express UART to a 390 ?
Alan
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] serial: forbid 8250 on s390
2017-12-12 15:50 ` Alan Cox
@ 2017-12-12 17:50 ` Christian Borntraeger
0 siblings, 0 replies; 5+ messages in thread
From: Christian Borntraeger @ 2017-12-12 17:50 UTC (permalink / raw)
To: Alan Cox
Cc: Greg Kroah-Hartman, Jiri Slaby, linux-serial, linux-s390, linux-kernel
On 12/12/2017 04:50 PM, Alan Cox wrote:
> On Tue, 12 Dec 2017 09:08:35 +0100
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>
>> Using "make kvmconfig" results in a potentially unusable linux image
>> on s390. The reason is that both the (default on s390) sclp consoles
>> as well as the 8250 console register a ttyS<x> as console. Since there
>> will be no 8250 on s390 let's fence 8250. This will ensure that there
>> is always a working sclp console.
>
> And there is no physical way to attach a PCI express UART to a 390 ?
There is (some sort of) PCI but these cards are packaged in ibm specific I/O cages.
So someone would need to apply some some serious hardware and firmware hacking (since
only IBM-approved PCi cards are allowed) and you would need to have an MSI-capable
8250 as well as an MSI capable driver. (we only support MSI, no classic interrupts)
In addition to that that 8250 probably needs to support virtual functions since we always
run with LPARs.
And even if we can solve all these issues I would say it really does not make any sense at
all, while the current situation obviously breaks the use case "make kvmconfig"
So unless IBM sees some serious business case for 8250, I am inclined to answer you
question with "no" :-)
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-12-12 17:50 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-12-12 8:08 [PATCH] serial: forbid 8250 on s390 Christian Borntraeger
2017-12-12 8:48 ` Greg Kroah-Hartman
2017-12-12 8:56 ` Christian Borntraeger
2017-12-12 15:50 ` Alan Cox
2017-12-12 17:50 ` Christian Borntraeger
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.