linux-kernel - Re: [PATCH v2 1/2] firmware: qcom: scm: Return -EOPNOTSUPP for unsupported SHM bridge enabling

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Message-ID: <CAMRc=MeiPbtHUQgJ5yR2EZbqRTS30zeuNEsXcgKdYt2c-X=fZA@mail.gmail.com>
Date: Mon, 14 Oct 2024 17:56:28 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kuldeep Singh <quic_kuldsing@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, linux-arm-msm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Qingqing Zhou <quic_qqzhou@...cinc.com>
Subject: Re: [PATCH v2 1/2] firmware: qcom: scm: Return -EOPNOTSUPP for
 unsupported SHM bridge enabling

On Mon, Oct 14, 2024 at 5:48 PM Kuldeep Singh <quic_kuldsing@...cinc.com> wrote:
>
>
> On 10/14/2024 6:35 PM, Bartosz Golaszewski wrote:
> > On Mon, Oct 14, 2024 at 1:19 PM Kuldeep Singh <quic_kuldsing@...cinc.com> wrote:
> >>
> >> From: Qingqing Zhou <quic_qqzhou@...cinc.com>
> >>
> >> When enabling SHM bridge, QTEE returns 0 and sets error 4 in result to
> >> qcom_scm for unsupported platforms. Currently, tzmem interprets this as
> >> an unknown error rather than recognizing it as an unsupported platform.
> >>
> >> Error log:
> >> [    0.177224] qcom_scm firmware:scm: error (____ptrval____): Failed to enable the TrustZone memory allocator
> >> [    0.177244] qcom_scm firmware:scm: probe with driver qcom_scm failed with error 4
> >>
> >> To address this, modify the function call qcom_scm_shm_bridge_enable()
> >> to remap result to indicate an unsupported error. This way, tzmem will
> >> correctly identify it as an unsupported platform case instead of
> >> reporting it as an error.
> >>
> >> Fixes: 178e19c0df1b ("firmware: qcom: scm: add support for SHM bridge operations")
> >> Signed-off-by: Qingqing Zhou <quic_qqzhou@...cinc.com>
> >> Co-developed-by: Kuldeep Singh <quic_kuldsing@...cinc.com>
> >> Signed-off-by: Kuldeep Singh <quic_kuldsing@...cinc.com>
> >> ---
> >>  drivers/firmware/qcom/qcom_scm.c | 13 ++++++++++++-
> >>  1 file changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> >> index 10986cb11ec0..0df81a9ed438 100644
> >> --- a/drivers/firmware/qcom/qcom_scm.c
> >> +++ b/drivers/firmware/qcom/qcom_scm.c
> >> @@ -112,6 +112,7 @@ enum qcom_scm_qseecom_tz_cmd_info {
> >>  };
> >>
> >>  #define QSEECOM_MAX_APP_NAME_SIZE              64
> >> +#define SHMBRIDGE_RESULT_NOTSUPP               4
> >>
> >>  /* Each bit configures cold/warm boot address for one of the 4 CPUs */
> >>  static const u8 qcom_scm_cpu_cold_bits[QCOM_SCM_BOOT_MAX_CPUS] = {
> >> @@ -1361,6 +1362,8 @@ EXPORT_SYMBOL_GPL(qcom_scm_lmh_dcvsh_available);
> >>
> >>  int qcom_scm_shm_bridge_enable(void)
> >>  {
> >> +       int ret;
> >> +
> >>         struct qcom_scm_desc desc = {
> >>                 .svc = QCOM_SCM_SVC_MP,
> >>                 .cmd = QCOM_SCM_MP_SHM_BRIDGE_ENABLE,
> >> @@ -1373,7 +1376,15 @@ int qcom_scm_shm_bridge_enable(void)
> >>                                           QCOM_SCM_MP_SHM_BRIDGE_ENABLE))
> >>                 return -EOPNOTSUPP;
> >>
> >> -       return qcom_scm_call(__scm->dev, &desc, &res) ?: res.result[0];
> >> +       ret = qcom_scm_call(__scm->dev, &desc, &res);
> >> +
> >> +       if (ret)
> >> +               return ret;
> >> +
> >> +       if (res.result[0] == SHMBRIDGE_RESULT_NOTSUPP)
> >> +               return -EOPNOTSUPP;
> >> +
> >> +       return res.result[0];
> >>  }
> >>  EXPORT_SYMBOL_GPL(qcom_scm_shm_bridge_enable);
> >>
> >> --
> >> 2.34.1
> >>
> >>
> >
> > The patch looks correct to me and like something that should go upstream.
> It's upstream mailing list only. Please see :)
>

Yes I know, by saying "go upstream" I mean "merged into mainline".

> >
> > Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>>
> > That being said, this doesn't seem to address any of the issues that
> > we saw with SHM Bridge and it still leads to a crash on sc8180x. :(
>
> Verified on qcs615, and qcs9100 by explicitly making shmbridge
> unsupported in QTEE and patch worked there.
> Sc,8180x is something different it seems as there's no scm driver probe
> failure and instead screen stuck is observed.
> I'd like to check this behavior and get rid off it from blacklist
> platform list.
>

Ah then my review is only more confident then. :)

Thanks,
Bartosz