linux-kernel - Re: [PATCH v3] rpmsg: qcom_smd: Access APCS through mailbox framework

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Date:   Fri, 31 Aug 2018 13:55:19 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-remoteproc@...r.kernel.org,
        Nicolas Dechesne <nicolas.dechesne@...aro.org>
Subject: Re: [PATCH v3] rpmsg: qcom_smd: Access APCS through mailbox framework

On Fri 31 Aug 13:41 PDT 2018, Frank Rowand wrote:

> On 08/30/18 21:07, Bjorn Andersson wrote:
> > On Thu 30 Aug 20:57 PDT 2018, Frank Rowand wrote:
> > 
> >> Hi Bjorn,
> >>
> >>
> >> On 04/19/18 18:17, Bjorn Andersson wrote:
> >>> Attempt to acquire the APCS IPC through the mailbox framework and fall
> >>> back to the old syscon based approach, to allow us to move away from
> >>> using the syscon.
> >>>
> >>> Reviewed-by: Arun Kumar Neelakantam <aneela@...eaurora.org>
> >>> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> >>> ---
> >>>
> >>> Changes since v2:
> >>> - Added comment about mbox_send_message() return value.
> >>>
> >>>  .../devicetree/bindings/soc/qcom/qcom,smd.txt      |  8 ++-
> >>>  drivers/rpmsg/Kconfig                              |  1 +
> >>>  drivers/rpmsg/qcom_smd.c                           | 67 ++++++++++++++++------
> >>>  3 files changed, 56 insertions(+), 20 deletions(-)
> >>
> >> This patch in the mainline Linux kernel as commit ab460a2e72dabecfdabd45eb7e3ee2d73fc876d4
> >> causes a problem with the APQ8074 Dragonboard.  The mmc device is not set up
> >> with the patch applied, thus I do not have the block device my root file system
> >> is located on.
> >>
> >> Testing on v4.18, if I revert this commit the mmc device is available.
> >>
> >> I'll reply to this email with the console messages for 4.18 and for 4.18 with
> >> this commit reverted.
> >>
> > 
> > The mmc device would fail to come up if the regulators didn't come up,
> > which would be the result of smd not working. But it should fallback to
> > the old mechanism if no mailbox is specified.
> > 
> > Can you double check that CONFIG_RPMSG_QCOM_SMD is still set in your
> > .config after applying and building with this commit included? And if
> > not, try to enable CONFIG_MAILBOX.
> 
> Thank you!
> 
> That is indeed the cause.  ab460a2e72da added a "depends on MAILBOX" to
> CONFIG_RPMSG_QCOM_SMD, so CONFIG_RPMSG_QCOM_SMD becomes unset since
> CONFIG_MAILBOX is not enabled in qcom_defconfig and is not otherwise
> selected for the dragonboard.
> 

Thanks for verifying this!

> Is there a config variable that should be selecting MAILBOX for a class
> of systems that would include the APQ8074 Dragonboard?  For my testing
> I added the "select MAILBOX" to CONFIG_ARCH_MSM8974, but I do not know
> what systems that includes, and whether it is appropriate to do the
> select for all of them.
> 

We typically don't use the CONFIG_ARCH_* to enable user selectable
config options, even if they serve a critical role in the system.

So minimum change would be to add CONFIG_MAILBOX to the qcom_defconfig
(and multi_v7_defconfig I presume). The fuller solution would be to add
qcom,msm8974-apcs-kpss-global (.data is 8) to the qcom-apcs-ipc-mailbox
list of compatibles and replace the syscon currently used, and then
enable these in the defconfigs.

Regards,
Bjorn