linux-kernel - Re: Regression caused by commit 882164a4a928

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Date:   Thu, 10 May 2018 11:24:12 +0100
From:   Matt Redfearn <matt.redfearn@...s.com>
To:     Michael Büsch <m@...s.ch>
CC:     Larry Finger <Larry.Finger@...inger.net>,
        Rafał Miłecki <zajec5@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Regression caused by commit 882164a4a928

Hi Michael,

On 09/05/18 17:27, Michael Büsch wrote:
> On Wed, 9 May 2018 13:55:43 +0100
> Matt Redfearn <matt.redfearn@...s.com> wrote:
> 
>> Hi Larry
>>
>> On 07/05/18 16:44, Larry Finger wrote:
>>> Matt,
>>>
>>> Although commit 882164a4a928 ("ssb: Prevent build of PCI host features
>>> in module") appeared to be harmless, it leads to complete failure of
>>> drivers b43. and b43legacy, and likely affects b44 as well. The problem
>>> is that CONFIG_SSB_PCIHOST is undefined, which prevents the compilation
>>> of the code that controls the PCI cores of the device. See
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1572349 for details.
>>
>> Sorry for the breakage :-/
>>
>>>
>>> As the underlying errors ("pcibios_enable_device" undefined, and
>>> "register_pci_controller" undefined) do not appear on the architectures
>>> that I have tested (x86_64, x86, and ppc), I suspect something in the
>>> arch-specific code for your setup (MIPS?). As I have no idea on how to
>>> fix that problem, would the following patch work for you?
>>>
>>> diff --git a/drivers/ssb/Kconfig b/drivers/ssb/Kconfig
>>> index 9371651d8017..3743533c8057 100644
>>> --- a/drivers/ssb/Kconfig
>>> +++ b/drivers/ssb/Kconfig
>>> @@ -117,7 +117,7 @@ config SSB_SERIAL
>>>
>>>    config SSB_DRIVER_PCICORE_POSSIBLE
>>>           bool
>>> -       depends on SSB_PCIHOST && SSB = y
>>> +       depends on SSB_PCIHOST && (SSB = y || !MIPS)
>>>           default y
>>>
>>>    config SSB_DRIVER_PCICORE
>>
>> I believe that the problem stems from these drivers being used for some
>> wireless AP functionality built into some MIPS based SoCs. The Kconfig
>> rules sort out building this additional functionality when configured
>> for MIPS (in a round about sort of way), but it allowed it even when SSB
>> is a module, leading to build failures. My patch was intended to prevent
>> that.
>>
>> There was a similar issue in the same Kconfig file, introduced by
>> c5611df96804 and fixed by a9e6d44ddecc. It was fixed the same way as you
>> suggest. I've tested the above patch and it does work for MIPS
>> (preventing the PCICORE being built into the module).
>>
>> Tested-by: Matt Redfearn <matt.redfearn@...s.com>
> 
> 
> Could you please try this?
> 
> config SSB_DRIVER_PCICORE_POSSIBLE
> 	depends on SSB_PCIHOST
> 
> config SSB_PCICORE_HOSTMODE
> 	depends on SSB_DRIVER_PCICORE && SSB_DRIVER_MIPS && (SSB = y) && PCI_DRIVERS_LEGACY
> 
> 
> The affected API pcibios_enable_device() and register_pci_controller()
> is only used in HOSTMODE. So I think it makes sense to make HOSTMODE
> depend on SSB=y and PCI_DRIVERS_LEGACY.
> 
> PCICore itself does not use the API, if hostmode is disabled.
> 

Sure - I've tested the patch:

--- a/drivers/ssb/Kconfig
+++ b/drivers/ssb/Kconfig
@@ -117,7 +117,7 @@ config SSB_SERIAL

  config SSB_DRIVER_PCICORE_POSSIBLE
         bool
-       depends on SSB_PCIHOST && SSB = y
+       depends on SSB_PCIHOST
         default y

  config SSB_DRIVER_PCICORE
@@ -131,7 +131,7 @@ config SSB_DRIVER_PCICORE

  config SSB_PCICORE_HOSTMODE
         bool "Hostmode support for SSB PCI core"
-       depends on SSB_DRIVER_PCICORE && SSB_DRIVER_MIPS
+       depends on SSB_DRIVER_PCICORE && SSB_DRIVER_MIPS && (SSB = y) && 
PCI_DRIVERS_LEGACY
         help
           PCIcore hostmode operation (external PCI bus).


And this seems to work for MIPS, we don't get the build error from 
building the SSB module under nec_markeins allmodconfig, and 
SSB_PCICORE_HOSTMODE=y for bcm47xx allmodconfig, which selects SSB=y.

So this looks like a good fix for MIPS, at least.

Tested-by: Matt Redfearn <matt.redfearn@...s.com>

Thanks,
Matt