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From:   Stephen Boyd <swboyd@chromium.org>
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Date:   Fri, 23 Jul 2021 19:28:13 +0000
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Subject: Re: [PATCH v4 1/2] soc: qcom: aoss: Expose send for generic usecase
To:     Deepak Kumar Singh <deesin@codeaurora.org>,
        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,
        Chris Lew <clew@codeaurora.org>
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Quoting Deepak Kumar Singh (2021-07-23 02:51:50)
>
> On 7/21/2021 12:07 PM, Stephen Boyd wrote:
> > 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.
>
> As per my earlier discussion with Bjorn, device could be unbound using
> sysfs, in which case
>
> remove() is called irrespective of whether any client driver is holding
> struct device reference
>
> or not. That's why i have added separate refcount for qmp handle and
> marking it invalid if
>
> qmp_remove() is called.
>

We have struct device_driver::suppress_bind_attrs for that. Can you set
it?