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Date: Sat, 10 Jul 2021 00:28:54 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Andy Gross <agross@...nel.org>, Rob Herring <robh+dt@...nel.org>,
Stephen Boyd <sboyd@...nel.org>,
Taniya Das <tdas@...eaurora.org>,
Jonathan Marek <jonathan@...ek.ca>,
Michael Turquette <mturquette@...libre.com>,
linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
linux-clk@...r.kernel.org,
Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
Mark Brown <broonie@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/7] clk: qcom: gdsc: enable optional power domain
support
On 09/07/2021 21:38, Bjorn Andersson wrote:
> On Fri 09 Jul 12:31 CDT 2021, Dmitry Baryshkov wrote:
>
>> On sm8250 dispcc and videocc registers are powered up by the MMCX power
>> domain. Currently we use a regulator to enable this domain on demand,
>> however this has some consequences, as genpd code is not reentrant.
>>
>> Teach Qualcomm clock controller code about setting up runtime PM and
>> using specified for gdsc powerup.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>> drivers/clk/qcom/common.c | 37 +++++++++++++++++++++++++++++++------
>> drivers/clk/qcom/gdsc.c | 4 ++++
>> 2 files changed, 35 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c
>> index 60d2a78d1395..43d8f8feeb3c 100644
>> --- a/drivers/clk/qcom/common.c
>> +++ b/drivers/clk/qcom/common.c
>> @@ -10,6 +10,7 @@
>> #include <linux/clk-provider.h>
>> #include <linux/reset-controller.h>
>> #include <linux/of.h>
>> +#include <linux/pm_runtime.h>
>>
>> #include "common.h"
>> #include "clk-rcg.h"
>> @@ -224,6 +225,11 @@ static struct clk_hw *qcom_cc_clk_hw_get(struct of_phandle_args *clkspec,
>> return cc->rclks[idx] ? &cc->rclks[idx]->hw : NULL;
>> }
>>
>> +static void qcom_cc_pm_runtime_disable(void *data)
>> +{
>> + pm_runtime_disable(data);
>> +}
>> +
>> int qcom_cc_really_probe(struct platform_device *pdev,
>> const struct qcom_cc_desc *desc, struct regmap *regmap)
>> {
>> @@ -241,6 +247,18 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>> if (!cc)
>> return -ENOMEM;
>>
>> + pm_runtime_enable(dev);
>
> In turingcc-qcs404.c I'm using pm_runtime to have the clock framework
> ensure that the iface clock is enabled during clock operations, so this
> will result in a "unbalanced enable" warning.
And later I register the disabler:
ret = devm_add_action_or_reset(dev, qcom_cc_pm_runtime_disable, dev);
You might want to add this to qcs404 code.
>
>> + ret = pm_runtime_get_sync(dev);
>
> I don't think you should wrap the entire initialization in a
> pm_runtime_get_sync()/put() region. Instead follow the clock framework
> and wrap gdsc initialization that needs to touch the hardware in:
Init should be wrapped in the pm_runtime_get/put calls, so that the MMCX
domain is on through the fall init sequence. Otherwise it can get turned
off during it, boom, failed register access and reboot.
>
> if (pm_runtime_enabled())
> pm_runtime_get_sync();
I don't think it's worth doing that. Having single lock for the whole
init sequence is safer (and cleaner).
If you check other pm-enabled drivers, they would either call
pm_runtime_enable at the end of the probe or get_sync in the beginning
of the probe and put_FOO in the end. In this driver calling
pm_runtime_enable() at the end of the probe function will not work,
since this way clk subsystem will not pick up the device for runtime
power management (as pm_runtime_enabled() would return false).
>
> I do however think that as of this patch, when probe returns MMCX might
> very well be turned off, as the only user (this driver) has pm_runtime
> enabled and it's idle. So I think you should introduce the
> pm_runtime_get()/put() in the gdsc functions before this patch.
Maybe I'd just squash them together.
>
>
> To summarize, I think you should rely on the individual clock drivers to
> pm_runtime_enable()/disable().
>
>> + if (ret < 0) {
>> + pm_runtime_put(dev);
>> + pm_runtime_disable(dev);
>> + return ret;
>> + }
>> +
>> + ret = devm_add_action_or_reset(dev, qcom_cc_pm_runtime_disable, dev);
>> + if (ret)
>> + goto err;
>> +
>> reset = &cc->reset;
>> reset->rcdev.of_node = dev->of_node;
>> reset->rcdev.ops = &qcom_reset_ops;
>> @@ -251,7 +269,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>>
>> ret = devm_reset_controller_register(dev, &reset->rcdev);
>> if (ret)
>> - return ret;
>> + goto err;
>>
>> if (desc->gdscs && desc->num_gdscs) {
>> scd = devm_kzalloc(dev, sizeof(*scd), GFP_KERNEL);
>> @@ -262,11 +280,11 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>> scd->num = desc->num_gdscs;
>> ret = gdsc_register(scd, &reset->rcdev, regmap);
>> if (ret)
>> - return ret;
>> + goto err;
>> ret = devm_add_action_or_reset(dev, qcom_cc_gdsc_unregister,
>> scd);
>> if (ret)
>> - return ret;
>> + goto err;
>> }
>>
>> cc->rclks = rclks;
>> @@ -277,7 +295,7 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>> for (i = 0; i < num_clk_hws; i++) {
>> ret = devm_clk_hw_register(dev, clk_hws[i]);
>> if (ret)
>> - return ret;
>> + goto err;
>> }
>>
>> for (i = 0; i < num_clks; i++) {
>> @@ -286,14 +304,21 @@ int qcom_cc_really_probe(struct platform_device *pdev,
>>
>> ret = devm_clk_register_regmap(dev, rclks[i]);
>> if (ret)
>> - return ret;
>> + goto err;
>> }
>>
>> ret = devm_of_clk_add_hw_provider(dev, qcom_cc_clk_hw_get, cc);
>> if (ret)
>> - return ret;
>> + goto err;
>> +
>> + pm_runtime_put(dev);
>>
>> return 0;
>> +
>> +err:
>> + pm_runtime_put(dev);
>> +
>> + return ret;
>> }
>> EXPORT_SYMBOL_GPL(qcom_cc_really_probe);
>>
>> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
>> index 51ed640e527b..ccd36617d067 100644
>> --- a/drivers/clk/qcom/gdsc.c
>> +++ b/drivers/clk/qcom/gdsc.c
>> @@ -439,6 +439,8 @@ int gdsc_register(struct gdsc_desc *desc,
>> continue;
>> if (scs[i]->parent)
>> pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd);
>> + else if (!IS_ERR_OR_NULL(dev->pm_domain))
>> + pm_genpd_add_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
>
> Nice, I didn't know that we could fish it out of the dev.
>
> Regards,
> Bjorn
>
>> }
>>
>> return of_genpd_add_provider_onecell(dev->of_node, data);
>> @@ -457,6 +459,8 @@ void gdsc_unregister(struct gdsc_desc *desc)
>> continue;
>> if (scs[i]->parent)
>> pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd);
>> + else if (!IS_ERR_OR_NULL(dev->pm_domain))
>> + pm_genpd_remove_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
>> }
>> of_genpd_del_provider(dev->of_node);
>> }
>> --
>> 2.30.2
>>
--
With best wishes
Dmitry
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