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From:   Stephen Boyd <swboyd@chromium.org>
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Date:   Wed, 21 Jul 2021 06:37:00 +0000
Message-ID: <CAE-0n506v5cmyUb+Ge-H7t1HsqNatgxDmq28rqdyGZDbsM4pXg@mail.gmail.com>
Subject: Re: [PATCH v4 1/2] soc: qcom: aoss: Expose send for generic usecase
To:     Sibi Sankar <sibis@codeaurora.org>, bjorn.andersson@linaro.org
Cc:     agross@kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, manivannan.sadhasivam@linaro.org,
        Deepak Kumar Singh <deesin@codeaurora.org>,
        Chris Lew <clew@codeaurora.org>
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Quoting Sibi Sankar (2021-06-09 04:18:51)
> From: Deepak Kumar Singh <deesin@codeaurora.org>
>
> Not all upcoming usecases will have an interface to allow the aoss
> driver to hook onto. Expose the send api and create a get function to
> enable drivers to send their own messages to aoss.
>
> Signed-off-by: Chris Lew <clew@codeaurora.org>
> Signed-off-by: Deepak Kumar Singh <deesin@codeaurora.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
> ---
>
> v4:
>  * Fix compilation error due to missing qmp_put
>  * Minor typos [s/tarcks/tracks]
>
>  drivers/soc/qcom/qcom_aoss.c       | 70 ++++++++++++++++++++++++++++++++++++--
>  include/linux/soc/qcom/qcom_aoss.h | 36 ++++++++++++++++++++
>  2 files changed, 104 insertions(+), 2 deletions(-)
>  create mode 100644 include/linux/soc/qcom/qcom_aoss.h
>
> diff --git a/drivers/soc/qcom/qcom_aoss.c b/drivers/soc/qcom/qcom_aoss.c
> index 934fcc4d2b05..e8f48760bac8 100644
> --- a/drivers/soc/qcom/qcom_aoss.c
> +++ b/drivers/soc/qcom/qcom_aoss.c
> @@ -522,13 +582,14 @@ static int qmp_probe(struct platform_device *pdev)
>         int irq;
>         int ret;
>
> -       qmp = devm_kzalloc(&pdev->dev, sizeof(*qmp), GFP_KERNEL);
> +       qmp = kzalloc(sizeof(*qmp), GFP_KERNEL);
>         if (!qmp)
>                 return -ENOMEM;
>
>         qmp->dev = &pdev->dev;
>         init_waitqueue_head(&qmp->event);
>         mutex_init(&qmp->tx_lock);
> +       kref_init(&qmp->refcount);
>
>         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>         qmp->msgram = devm_ioremap_resource(&pdev->dev, res);
> @@ -569,6 +630,8 @@ static int qmp_probe(struct platform_device *pdev)
>
>         platform_set_drvdata(pdev, qmp);
>
> +       atomic_set(&qmp->orphan, 0);
> +
>         return 0;
>
>  err_remove_qdss_clk:
> @@ -577,6 +640,7 @@ static int qmp_probe(struct platform_device *pdev)
>         qmp_close(qmp);
>  err_free_mbox:
>         mbox_free_channel(qmp->mbox_chan);
> +       kfree(qmp);
>
>         return ret;
>  }
> @@ -590,7 +654,9 @@ static int qmp_remove(struct platform_device *pdev)
>         qmp_cooling_devices_remove(qmp);
>
>         qmp_close(qmp);
> +       atomic_set(&qmp->orphan, 1);

This looks odd. Why are we letting the device be removed while it is in
use by other drivers? Can't we pin the device with get_device() so it
can't be removed and then prevent the driver from being removed until
all the consumer drivers drop the reference, i.e. suppress sysfs unbind?

Otherwise it looks like a generic problem that all provider devices,
clks, regulators, gpios, etc. have to deal with and thus this
hand-rolled mechanism can't be right.

>         mbox_free_channel(qmp->mbox_chan);
> +       kref_put(&qmp->refcount, qmp_handle_release);
>
>         return 0;
>  }