linux-kernel - Re: [PATCH] coresight replicator: set default y after Kconfig rename

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Date:   Thu, 8 Feb 2018 11:53:44 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kim Phillips <kim.phillips@....com>,
        Robin Murphy <robin.murphy@....com>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH] coresight replicator: set default y after Kconfig rename

On 02/08/2018 11:23 AM, Kim Phillips wrote:
> On Thu, 8 Feb 2018 16:13:16 +0000
> Robin Murphy <robin.murphy@....com> wrote:
> 
>> On 07/02/18 21:03, Kim Phillips wrote:
>>> Commit 1c8859848dbb ("coresight replicator: Cleanup programmable
>>> replicator naming") changed the Kconfig symbol name from
>>> QCOM_REPLICATOR, which, whilst not in the single arm64 defconfig,
>>> was being set in my juno build script, which left the new symbol unset,
>>> causing the following unexpected grief:
>>>
>>>   # ./perf record -vvv -C 0 -e cs_etm/@...70000.etr/ --per-thread true
>>>   ..<snip>..
>>>   sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 5
>>>   mmap size 528384B
>>>   AUX area mmap length 4194304
>>>   perf event ring buffer mmapped per cpu
>>>   failed to mmap AUX area
>>>   failed to mmap with 12 (Cannot allocate memory)
>>>
>>> Make it default y to help not surprise unsuspecting users.
>>
>> How many users are there relying on your Juno build script? :P
> 
> This shouldn't be that uncommon for coresight users:
> 
> make defconfig
> scripts/config -e CONFIG_CORESIGHT
> scripts/config -e CONFIG_CORESIGHT_LINK_AND_SINK_TMC
> scripts/config -e CONFIG_CORESIGHT_SINK_TPIU
> scripts/config -e CONFIG_CORESIGHT_SINK_ETBV10
> scripts/config -e CONFIG_CORESIGHT_LINKS_AND_SINKS
> scripts/config -e CONFIG_CORESIGHT_SOURCE_ETM3X
> scripts/config -e CONFIG_CORESIGHT_SOURCE_ETM4X
> #scripts/config -e CONFIG_CORESIGHT_QCOM_REPLICATOR
> scripts/config -e CONFIG_CORESIGHT_DYNAMIC_REPLICATOR
> scripts/config -e CONFIG_CORESIGHT_STM
> scripts/config -e CONFIG_CORESIGHT_CPU_DEBUG
> 
> FWIW, Mathieu - who helped me track the cannot allocate memory problem
> down to this config symbol - has also benn caught by this issue.
> 
>>> Fixes: 1c8859848dbb ("coresight replicator: Cleanup programmable replicator naming")
>>
>> Before that commit, CORESIGHT_QCOM_REPLICATOR was not "default y", nor 
>> selected by any in-tree configs, so whatever the problem may be this is 
>> clearly not the correct fix.
> 
> Well, there's only one defconfig for arm64.  I don't know why it
> doesn't set CORESIGHT, but you're right, this is taking the build fix
> one step further to facilitate user coresight configuration.  I can
> change the patch to make the change to the arm64 defconfig, but I still
> believe CORESIGHT_DYNAMIC_REPLICATOR should be default=y, and the
> defconfig just set CORESIGHT.
> 
>>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>>> Signed-off-by: Kim Phillips <kim.phillips@....com>
>>> ---
>>>   drivers/hwtracing/coresight/Kconfig | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
>>> index ef9cb3c164e1..b94bbd95efa6 100644
>>> --- a/drivers/hwtracing/coresight/Kconfig
>>> +++ b/drivers/hwtracing/coresight/Kconfig
>>> @@ -73,6 +73,7 @@ config CORESIGHT_SOURCE_ETM4X
>>>   config CORESIGHT_DYNAMIC_REPLICATOR
>>>   	bool "CoreSight Programmable Replicator driver"
>>>   	depends on CORESIGHT_LINKS_AND_SINKS
>>> +	default y
>>
>> CORESIGHT_LINKS_AND_SINKS is "default n" (as indeed is CORESIGHT), and 
>> not selected by any defconfigs, so in general this doesn't really help 
>> anyway.
> 
> Yeah, CORESIGHT_LINKS_AND_SINKS should probably be default y too.

Are they required for system operation?  If not, they should not default to y.

and if they are required, it seems odd that they are in drivers/hwtracing/.


-- 
~Randy