linux-kernel - Re: [PATCH v4 1/2] PCI: qcom: Add system PM support

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Date:   Fri, 15 Jul 2022 15:43:01 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     helgaas@...nel.org, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        mka@...omium.org, quic_vbadigan@...cinc.com,
        quic_hemantk@...cinc.com, quic_nitegupt@...cinc.com,
        quic_skananth@...cinc.com, quic_ramkri@...cinc.com,
        manivannan.sadhasivam@...aro.org, swboyd@...omium.org,
        dmitry.baryshkov@...aro.org,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v4 1/2] PCI: qcom: Add system PM support

On Wed, Jul 06, 2022 at 08:10:24PM +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.
 
> 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.

Changelogs typically go below the --- line below so that they don't end
up in the git logs.
 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 85 ++++++++++++++++++++++++++++++++++
>  1 file changed, 85 insertions(+)

> +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;
> +
> +	clk_prepare_enable(res->pipe_clk);

Note that pipe clock management has now been removed from this driver.

Please consider rebasing on this branch:

	https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/ctrl/qcom

> +
> +	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
> +
> +	phy_power_on(pcie->phy);
> +
> +	return ret;
> +}

Johan