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Message-ID: <c52f0311-a8a0-79af-2a08-51a8564a8b25@linaro.org>
Date: Sat, 10 Jun 2023 21:39:00 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Stephan Gerhold <stephan@...hold.net>
Cc: Andy Gross <agross@...nel.org>,
Bjorn Andersson <andersson@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>,
Georgi Djakov <djakov@...nel.org>,
Leo Yan <leo.yan@...aro.org>,
Evan Green <evgreen@...omium.org>,
Marijn Suijten <marijn.suijten@...ainline.org>,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-clk@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [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@...aro.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@...hold.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@...hold.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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