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Message-ID: <be3ff287-56bc-1d71-3ae9-da6a9658479d@quicinc.com>
Date:   Wed, 24 Aug 2022 08:58:47 +0530
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Subject: Re: [PATCH v5 1/3] PCI: qcom: Add system PM support
Content-Language: en-US
To:     Rob Herring <robh@kernel.org>
CC:     <helgaas@kernel.org>, <linux-pci@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <mka@chromium.org>, <quic_vbadigan@quicinc.com>,
        <quic_hemantk@quicinc.com>, <quic_nitegupt@quicinc.com>,
        <quic_skananth@quicinc.com>, <quic_ramkri@quicinc.com>,
        <manivannan.sadhasivam@linaro.org>, <swboyd@chromium.org>,
        <dmitry.baryshkov@linaro.org>,
        Stanimir Varbanov <svarbanov@mm-sol.com>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= <kw@linux.com>,
        Bjorn Helgaas <bhelgaas@google.com>
References: <1659526134-22978-1-git-send-email-quic_krichai@quicinc.com>
 <1659526134-22978-2-git-send-email-quic_krichai@quicinc.com>
 <20220810215022.GC557589-robh@kernel.org>
From:   Krishna Chaitanya Chundru <quic_krichai@quicinc.com>
In-Reply-To: <20220810215022.GC557589-robh@kernel.org>
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On 8/11/2022 3:20 AM, Rob Herring wrote:
> On Wed, Aug 03, 2022 at 04:58:52PM +0530, Krishna chaitanya chundru wrote:
>> Add suspend and resume pm callbacks.
>>
>> When system suspends, and if the link is in L1ss, disable the clocks
>> and power down the phy so that system enters into low power state to
>> save the maximum power. And when the system resumes, enable the clocks
>> back and power on phy if they are disabled in the suspend path.
>>
>> we are doing this only when link is in l1ss but not in L2/L3 as
>> no where we are forcing link to L2/L3 by sending PME turn off.
>>
>> is_suspended flag indicates if the clocks are disabled in the suspend
>> path or not. And this flag is being used to restrict the access to
>> config space, dbi etc when clock are turned-off.
>>
>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
>> ---
>> Changes since v4:
>> 	- Rebasing the code and removed the supports_system_suspend flag
>> 	- in the resume path as is_suspended will serve its purpose.
>> Changes since v3:
>> 	- Powering down the phy in suspend and powering it on resume to
>> 	  acheive maximum power savings.
>> Changes since v2:
>> 	- Replaced the enable, disable clks ops with suspend and resume
>> 	- Renamed support_pm_opsi flag  with supports_system_suspend.
>> Changes since v1:
>> 	- Fixed compilation errors.
>> ---
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 76 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 76 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index ccf6953..9dd50fc0 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -44,6 +44,9 @@
>>   #define PCIE20_PARF_PM_CTRL			0x20
>>   #define REQ_NOT_ENTR_L1				BIT(5)
>>   
>> +#define PCIE20_PARF_PM_STTS			0x24
>> +#define PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB	BIT(8)
>> +
>>   #define PCIE20_PARF_PHY_CTRL			0x40
>>   #define PHY_CTRL_PHY_TX0_TERM_OFFSET_MASK	GENMASK(20, 16)
>>   #define PHY_CTRL_PHY_TX0_TERM_OFFSET(x)		((x) << 16)
>> @@ -211,6 +214,8 @@ struct qcom_pcie_ops {
>>   	void (*post_deinit)(struct qcom_pcie *pcie);
>>   	void (*ltssm_enable)(struct qcom_pcie *pcie);
>>   	int (*config_sid)(struct qcom_pcie *pcie);
>> +	int (*suspend)(struct qcom_pcie *pcie);
>> +	int (*resume)(struct qcom_pcie *pcie);
> This is really the wrong direction. We don't need the DWC driver
> defining per platform ops and then a platform defining sub-platform ops.
> IOW, qcom_pcie_ops should go away.
>
> But for now, you don't even need the ops as only 1 version is
> implemented. Do you really expect other versions to do something
> different than turn off clocks and phys?
We will remove this in next patch.
>
>>   };
>>   
>>   struct qcom_pcie_cfg {
>> @@ -219,6 +224,7 @@ struct qcom_pcie_cfg {
>>   	unsigned int has_ddrss_sf_tbu_clk:1;
>>   	unsigned int has_aggre0_clk:1;
>>   	unsigned int has_aggre1_clk:1;
>> +	unsigned int supports_system_suspend:1;
>>   };
>>   
>>   struct qcom_pcie {
>> @@ -229,6 +235,7 @@ struct qcom_pcie {
>>   	struct phy *phy;
>>   	struct gpio_desc *reset;
>>   	const struct qcom_pcie_cfg *cfg;
>> +	unsigned int is_suspended:1;
>>   };
>>   
>>   #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
>> @@ -1297,6 +1304,29 @@ static void qcom_pcie_deinit_2_7_0(struct qcom_pcie *pcie)
>>   	regulator_bulk_disable(ARRAY_SIZE(res->supplies), res->supplies);
>>   }
>>   
>> +static int qcom_pcie_resume_2_7_0(struct qcom_pcie *pcie)
>> +{
>> +	struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
>> +	int ret;
>> +
>> +	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
>> +
>> +	phy_power_on(pcie->phy);
>> +
>> +	return ret;
>> +}
>> +
>> +static int qcom_pcie_suspend_2_7_0(struct qcom_pcie *pcie)
>> +{
>> +	struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
>> +
>> +	phy_power_off(pcie->phy);
>> +
>> +	clk_bulk_disable_unprepare(res->num_clks, res->clks);
>> +
>> +	return 0;
>> +}
>> +
>>   static int qcom_pcie_get_resources_2_9_0(struct qcom_pcie *pcie)
>>   {
>>   	struct qcom_pcie_resources_2_9_0 *res = &pcie->res.v2_9_0;
>> @@ -1590,6 +1620,8 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
>>   	.deinit = qcom_pcie_deinit_2_7_0,
>>   	.ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
>>   	.config_sid = qcom_pcie_config_sid_sm8250,
>> +	.suspend = qcom_pcie_suspend_2_7_0,
>> +	.resume = qcom_pcie_resume_2_7_0,
>>   };
>>   
>>   /* Qcom IP rev.: 2.9.0  Synopsys IP rev.: 5.00a */
>> @@ -1655,6 +1687,7 @@ static const struct qcom_pcie_cfg sm8450_pcie1_cfg = {
>>   static const struct qcom_pcie_cfg sc7280_cfg = {
>>   	.ops = &ops_1_9_0,
>>   	.has_tbu_clk = true,
>> +	.supports_system_suspend = true,
>>   };
>>   
>>   static const struct qcom_pcie_cfg sc8180x_cfg = {
>> @@ -1760,6 +1793,48 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>   	return ret;
>>   }
>>   
>> +static int __maybe_unused qcom_pcie_pm_suspend(struct device *dev)
>> +{
>> +	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>> +	u32 val;
>> +
>> +	if (!pcie->cfg->supports_system_suspend)
>> +		return 0;
>> +
>> +	/* if the link is not in l1ss don't turn off clocks */
>> +	val = readl(pcie->parf + PCIE20_PARF_PM_STTS);
>> +	if (!(val & PCIE20_PARF_PM_STTS_LINKST_IN_L1SUB)) {
>> +		dev_warn(dev, "Link is not in L1ss\n");
>> +		return 0;
>> +	}
> If anything, this looks like the version specific code.

This is common for all qcom specific code. Here we are checking for link 
is in l1ss or not

If the link is present in l1ss only we go ahead turn off clocks and phy.

>
>> +
>> +	if (pcie->cfg->ops->suspend)
>> +		pcie->cfg->ops->suspend(pcie);
>> +
>> +	pcie->is_suspended = true;
>> +
>> +	return 0;
>> +}
>> +
>> +static int __maybe_unused qcom_pcie_pm_resume(struct device *dev)
>> +{
>> +	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>> +
>> +	if (!pcie->is_suspended)
>> +		return 0;
> Pretty sure the driver core should take care of not calling resume if
> not suspended.

We are returning success in suspend call even if we didn't turn off 
clocks/phy. so I am using

this flag to know the clocks are off/not.

>
>> +
>> +	if (pcie->cfg->ops->resume)
>> +		pcie->cfg->ops->resume(pcie);
>> +
>> +	pcie->is_suspended = false;
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct dev_pm_ops qcom_pcie_pm_ops = {
>> +	NOIRQ_SYSTEM_SLEEP_PM_OPS(qcom_pcie_pm_suspend, qcom_pcie_pm_resume)
>> +};
>> +
>>   static const struct of_device_id qcom_pcie_match[] = {
>>   	{ .compatible = "qcom,pcie-apq8084", .data = &apq8084_cfg },
>>   	{ .compatible = "qcom,pcie-ipq8064", .data = &ipq8064_cfg },
>> @@ -1796,6 +1871,7 @@ static struct platform_driver qcom_pcie_driver = {
>>   	.probe = qcom_pcie_probe,
>>   	.driver = {
>>   		.name = "qcom-pcie",
>> +		.pm = pm_sleep_ptr(&qcom_pcie_pm_ops),
>>   		.suppress_bind_attrs = true,
>>   		.of_match_table = qcom_pcie_match,
>>   	},
>> -- 
>> 2.7.4
>>