linux-kernel - Re: [PATCH 2/3] PCI: dwc: qcom: Set suspend

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Date:   Mon, 16 May 2022 15:19:50 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     bhelgaas@...gle.com, lorenzo.pieralisi@....com, kbusch@...nel.org,
        hch@....de, linux-nvme@...ts.infradead.org,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, svarbanov@...sol.com,
        bjorn.andersson@...aro.org, axboe@...com,
        quic_vbadigan@...cinc.com, quic_krichai@...cinc.com,
        quic_nitirawa@...cinc.com, vidyas@...dia.com, sagi@...mberg.me
Subject: Re: [PATCH 2/3] PCI: dwc: qcom: Set suspend_poweroff flag for SC7280

On Fri, May 13, 2022 at 04:30:26PM +0530, Manivannan Sadhasivam wrote:
> For aggressive power saving on SC7280 SoCs, the power for the PCI devices
> will be taken off during system suspend. Hence, notify the same to the
> PCI device drivers using "suspend_poweroff" flag so that the drivers can
> prepare the PCI devices to handle the poweroff and recover them during
> resume.

No doubt "power ... will be taken off during system suspend" is true,
but this isn't very informative.  Is this a property of SC7280?  A
choice made by the SC7280 driver?  Why is this not applicable to other
systems?

> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 6ab90891801d..4b0ad2827f8f 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -199,6 +199,7 @@ 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 suspend_poweroff:1;
>  };
>  
>  struct qcom_pcie {
> @@ -1220,6 +1221,10 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
>  	if (pcie->cfg->pipe_clk_need_muxing)
>  		clk_set_parent(res->pipe_clk_src, res->ref_clk_src);
>  
> +	/* Indicate PCI device drivers that the power will be taken off during system suspend */
> +	if (pcie->cfg->suspend_poweroff)
> +		pci->pp.bridge->suspend_poweroff = true;
> +
>  	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
>  	if (ret < 0)
>  		goto err_disable_regulators;
> @@ -1548,6 +1553,7 @@ static const struct qcom_pcie_cfg sc7280_cfg = {
>  	.ops = &ops_1_9_0,
>  	.has_tbu_clk = true,
>  	.pipe_clk_need_muxing = true,
> +	.suspend_poweroff = true,
>  };
>  
>  static const struct dw_pcie_ops dw_pcie_ops = {
> -- 
> 2.25.1
>