linux-kernel - Re: [PATCH 5.10 14/49] net: ipa: ignore CHANNEL_NOT

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Date:   Wed, 10 Mar 2021 11:48:03 -0600
From:   Alex Elder <elder@...aro.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux-stable <stable@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>, lkft-triage@...ts.linaro.org
Subject: Re: [PATCH 5.10 14/49] net: ipa: ignore CHANNEL_NOT_RUNNING errors

On 3/10/21 11:36 AM, Naresh Kamboju wrote:
> On Wed, 10 Mar 2021 at 18:56, <gregkh@...uxfoundation.org> wrote:
>>
>> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>
>> From: Alex Elder <elder@...aro.org>
>>
>> [ Upstream commit f849afcc8c3b27d7b50827e95b60557f24184df0 ]

Upstream commit f849afcc8c3b27d7b5 is described as:
   v5.10-rc4-1094-gf849afcc8c3b2
Is this being "back-ported" to v5.10 stable?

Maybe I'm confused.

					-Alex

>> IPA v4.2 has a hardware quirk that requires the AP to allocate GSI
>> channels for the modem to use.  It is recommended that these modem
>> channels get stopped (with a HALT generic command) by the AP when
>> its IPA driver gets removed.
>>
>> The AP has no way of knowing the current state of a modem channel.
>> So when the IPA driver issues a HALT command it's possible the
>> channel is not running, and in that case we get an error indication.
>> This error simply means we didn't need to stop the channel, so we
>> can ignore it.
>>
>> This patch adds an explanation for this situation, and arranges for
>> this condition to *not* report an error message.
>>
>> Signed-off-by: Alex Elder <elder@...aro.org>
>> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>   drivers/net/ipa/gsi.c | 24 +++++++++++++++++++++++-
>>   1 file changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
>> index 2a65efd3e8da..48ee43b89fec 100644
>> --- a/drivers/net/ipa/gsi.c
>> +++ b/drivers/net/ipa/gsi.c
>> @@ -1052,10 +1052,32 @@ static void gsi_isr_gp_int1(struct gsi *gsi)
>>          u32 result;
>>          u32 val;
>>
>> +       /* This interrupt is used to handle completions of the two GENERIC
>> +        * GSI commands.  We use these to allocate and halt channels on
>> +        * the modem's behalf due to a hardware quirk on IPA v4.2.  Once
>> +        * allocated, the modem "owns" these channels, and as a result we
>> +        * have no way of knowing the channel's state at any given time.
>> +        *
>> +        * It is recommended that we halt the modem channels we allocated
>> +        * when shutting down, but it's possible the channel isn't running
>> +        * at the time we issue the HALT command.  We'll get an error in
>> +        * that case, but it's harmless (the channel is already halted).
>> +        *
>> +        * For this reason, we silently ignore a CHANNEL_NOT_RUNNING error
>> +        * if we receive it.
>> +        */
>>          val = ioread32(gsi->virt + GSI_CNTXT_SCRATCH_0_OFFSET);
>>          result = u32_get_bits(val, GENERIC_EE_RESULT_FMASK);
>> -       if (result != GENERIC_EE_SUCCESS_FVAL)
>> +
>> +       switch (result) {
>> +       case GENERIC_EE_SUCCESS_FVAL:
>> +       case GENERIC_EE_CHANNEL_NOT_RUNNING_FVAL:
> 
> 
> While building stable rc 5.10 for arm64 the build failed due to
> the following errors / warnings.
> 
> make --silent --keep-going --jobs=8
> O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=arm64
> CROSS_COMPILE=aarch64-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> clang'
> drivers/net/ipa/gsi.c:1074:7: error: use of undeclared identifier
> 'GENERIC_EE_CHANNEL_NOT_RUNNING_FVAL'
>          case GENERIC_EE_CHANNEL_NOT_RUNNING_FVAL:
>               ^
> 1 error generated.
> make[4]: *** [scripts/Makefile.build:279: drivers/net/ipa/gsi.o] Error 1
> 
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> 
> Build log link,
> https://gitlab.com/Linaro/lkft/mirrors/stable/linux-stable-rc/-/jobs/1086862412#L210
>