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

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Date:   Wed, 10 Mar 2021 23:06:09 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>, Alex Elder <elder@...aro.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 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 ]
>
> 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

-- 
Linaro LKFT
https://lkft.linaro.org