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    SubjectRe: [PATCH v2 04/22] clk: qcom: smd-rpm: Export clock scaling availability


    On 10.06.2023 21:25, Stephan Gerhold wrote:
    > On Sat, Jun 10, 2023 at 08:53:05PM +0200, Konrad Dybcio wrote:
    >> On 10.06.2023 14:15, Konrad Dybcio wrote:
    >>> On 10.06.2023 13:35, Stephan Gerhold wrote:
    >>>> On Fri, Jun 09, 2023 at 10:19:09PM +0200, Konrad Dybcio wrote:
    >>>>> Before we issue a call to RPM through clk_smd_rpm_enable_scaling() the
    >>>>> clock rate requests will not be commited in hardware. This poses a
    >>>>> race threat since we're accessing the bus clocks directly from within
    >>>>> the interconnect framework.
    >>>>>
    >>>>> Add a marker to indicate that we're good to go with sending new requests
    >>>>> and export it so that it can be referenced from icc.
    >>>>>
    >>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
    >>>>> ---
    >>>>> drivers/clk/qcom/clk-smd-rpm.c | 9 +++++++++
    >>>>> include/linux/soc/qcom/smd-rpm.h | 2 ++
    >>>>> 2 files changed, 11 insertions(+)
    >>>>>
    >>>>> diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
    >>>>> index 937cb1515968..482fe30ee6f0 100644
    >>>>> --- a/drivers/clk/qcom/clk-smd-rpm.c
    >>>>> +++ b/drivers/clk/qcom/clk-smd-rpm.c
    >>>>> @@ -151,6 +151,7 @@
    >>>>> #define to_clk_smd_rpm(_hw) container_of(_hw, struct clk_smd_rpm, hw)
    >>>>>
    >>>>> static struct qcom_smd_rpm *rpmcc_smd_rpm;
    >>>>> +static bool smd_rpm_clk_scaling;
    >>>>>
    >>>>> struct clk_smd_rpm {
    >>>>> const int rpm_res_type;
    >>>>> @@ -385,6 +386,12 @@ static unsigned long clk_smd_rpm_recalc_rate(struct clk_hw *hw,
    >>>>> return r->rate;
    >>>>> }
    >>>>>
    >>>>> +bool qcom_smd_rpm_scaling_available(void)
    >>>>> +{
    >>>>> + return smd_rpm_clk_scaling;
    >>>>> +}
    >>>>> +EXPORT_SYMBOL_GPL(qcom_smd_rpm_scaling_available);
    >>>>> +
    >>>>> static int clk_smd_rpm_enable_scaling(void)
    >>>>> {
    >>>>> int ret;
    >>>>> @@ -410,6 +417,8 @@ static int clk_smd_rpm_enable_scaling(void)
    >>>>> return ret;
    >>>>> }
    >>>>>
    >>>>> + smd_rpm_clk_scaling = true;
    >>>>> +
    >>>>
    >>>> If you move the platform_device_register_data(&rpdev->dev,
    >>>> "icc_smd_rpm", ...) from drivers/soc/qcom/smd-rpm.c to here you can
    >>>> avoid the race completely and drop this API. I think that would be
    >>>> cleaner. And it will likely probe much faster because probe deferral
    >>>> is slow. :)
    >>> Sounds like an idea.. especially since it's pretty much the only
    >>> dependency other than SMDRPM itself!
    >> It sounds great, but to not break bisecting one has to:
    >>
    >> 1. change the registration in soc/smd-rpm to store rpm ptr in driver
    >> data, in addition to parent driver data
    >>
    >> 2. change icc/smd-rpm to use the device and not parent data
    >>
    >> 3. add a platform_device_register_data call in clk-smd-rpm that will
    >> always fail because the device is always registered
    >>
    >> 4. remove the registration from soc/smd-rpm
    >>
    >
    > Logically the icc_smd_rpm device still fits better as child of
    > smd-rpm and not clk-smd-rpm. So I would probably just continue
    > registering it on the parent device from clk-smd-rpm.
    > Then there are no changes necessary in icc_smd_rpm.
    >
    > You could use this. Both touched files are Bjorn-maintained so should be
    > manageable to have it in one commit. (note: compile-tested only)
    >
    > Thanks,
    > Stephan
    >
    > From a2610adb2551b01e76b9de8e4cbcc89853814a8f Mon Sep 17 00:00:00 2001
    > From: Stephan Gerhold <stephan@gerhold.net>
    > Date: Sat, 10 Jun 2023 21:19:48 +0200
    > Subject: [PATCH] soc: qcom: smd-rpm: Move icc_smd_rpm registration to
    > clk-smd-rpm
    >
    > icc_smd_rpm will do bus clock votes itself rather than taking the
    > unnecessary detour through the clock subsystem. However, it can only
    > do that after the clocks have been handed off and scaling has been
    > enabled in the RPM in clk-smd-rpm.
    >
    > Move the icc_smd_rpm registration from smd-rpm.c to clk-smd-rpm.c
    > to avoid any possible races. icc_smd_rpm gets the driver data from
    > the smd-rpm device, so still register the platform device on the
    > smd-rpm parent device.
    >
    > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
    > ---
    Generally it looks good.. I'll give it a spin next week. One
    thing below.

    > drivers/clk/qcom/clk-smd-rpm.c | 21 +++++++++++++++++++++
    > drivers/soc/qcom/smd-rpm.c | 23 +----------------------
    > 2 files changed, 22 insertions(+), 22 deletions(-)
    >
    > diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
    > index e4de74b68797..91adb16889b3 100644
    > --- a/drivers/clk/qcom/clk-smd-rpm.c
    > +++ b/drivers/clk/qcom/clk-smd-rpm.c
    > @@ -1302,12 +1302,20 @@ static struct clk_hw *qcom_smdrpm_clk_hw_get(struct of_phandle_args *clkspec,
    > return desc->clks[idx] ? &desc->clks[idx]->hw : ERR_PTR(-ENOENT);
    > }
    >
    > +static void rpm_smd_unregister_icc(void *data)
    > +{
    > + struct platform_device *icc_pdev = data;
    > +
    > + platform_device_unregister(icc_pdev);
    > +}
    > +
    > static int rpm_smd_clk_probe(struct platform_device *pdev)
    > {
    > int ret;
    > size_t num_clks, i;
    > struct clk_smd_rpm **rpm_smd_clks;
    > const struct rpm_smd_clk_desc *desc;
    > + struct platform_device *icc_pdev;
    >
    > rpmcc_smd_rpm = dev_get_drvdata(pdev->dev.parent);
    > if (!rpmcc_smd_rpm) {
    > @@ -1357,6 +1365,19 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
    > if (ret)
    > goto err;
    >
    > + icc_pdev = platform_device_register_data(pdev->dev.parent,
    > + "icc_smd_rpm", -1, NULL, 0);
    > + if (IS_ERR(icc_pdev)) {
    > + dev_err(&pdev->dev, "Failed to register icc_smd_rpm device: %pE\n",
    > + icc_pdev);
    > + /* No need to unregister clocks because of this */
    > + } else {
    > + ret = devm_add_action_or_reset(&pdev->dev, rpm_smd_unregister_icc,
    > + icc_pdev);
    > + if (ret)
    > + goto err;
    > + }
    > +
    > return 0;
    > err:
    > dev_err(&pdev->dev, "Error registering SMD clock driver (%d)\n", ret);
    > diff --git a/drivers/soc/qcom/smd-rpm.c b/drivers/soc/qcom/smd-rpm.c
    > index 0c1aa809cc4e..427dd5392b82 100644
    > --- a/drivers/soc/qcom/smd-rpm.c
    > +++ b/drivers/soc/qcom/smd-rpm.c
    > @@ -19,7 +19,6 @@
    > /**
    > * struct qcom_smd_rpm - state of the rpm device driver
    > * @rpm_channel: reference to the smd channel
    > - * @icc: interconnect proxy device
    > * @dev: rpm device
    > * @ack: completion for acks
    > * @lock: mutual exclusion around the send/complete pair
    > @@ -27,7 +26,6 @@
    > */
    > struct qcom_smd_rpm {
    > struct rpmsg_endpoint *rpm_channel;
    > - struct platform_device *icc;
    > struct device *dev;
    >
    > struct completion ack;
    > @@ -197,7 +195,6 @@ static int qcom_smd_rpm_callback(struct rpmsg_device *rpdev,
    > static int qcom_smd_rpm_probe(struct rpmsg_device *rpdev)
    > {
    > struct qcom_smd_rpm *rpm;
    > - int ret;
    >
    > rpm = devm_kzalloc(&rpdev->dev, sizeof(*rpm), GFP_KERNEL);
    > if (!rpm)
    > @@ -210,24 +207,7 @@ static int qcom_smd_rpm_probe(struct rpmsg_device *rpdev)
    > rpm->rpm_channel = rpdev->ept;
    > dev_set_drvdata(&rpdev->dev, rpm);
    >
    > - rpm->icc = platform_device_register_data(&rpdev->dev, "icc_smd_rpm", -1,
    > - NULL, 0);
    > - if (IS_ERR(rpm->icc))
    > - return PTR_ERR(rpm->icc);
    > -
    > - ret = of_platform_populate(rpdev->dev.of_node, NULL, NULL, &rpdev->dev);
    > - if (ret)
    > - platform_device_unregister(rpm->icc);
    > -
    > - return ret;
    > -}
    > -
    > -static void qcom_smd_rpm_remove(struct rpmsg_device *rpdev)
    > -{
    > - struct qcom_smd_rpm *rpm = dev_get_drvdata(&rpdev->dev);
    > -
    > - platform_device_unregister(rpm->icc);
    > - of_platform_depopulate(&rpdev->dev);
    > + return devm_of_platform_populate(&rpdev->dev);
    > }
    >
    > static const struct of_device_id qcom_smd_rpm_of_match[] = {
    > @@ -256,7 +236,6 @@ MODULE_DEVICE_TABLE(of, qcom_smd_rpm_of_match);
    >
    > static struct rpmsg_driver qcom_smd_rpm_driver = {
    > .probe = qcom_smd_rpm_probe,
    > - .remove = qcom_smd_rpm_remove,
    This reaches over the removal of the icc registration, the depopulate
    call should stay.

    Konrad
    > .callback = qcom_smd_rpm_callback,
    > .drv = {
    > .name = "qcom_smd_rpm",

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