Re: [PATCH v2 4/4] PCI: imx: Add PME_Turn_Off support

[Lucas Stach]

Am Donnerstag, den 04.10.2018, 16:34 +0000 schrieb Leonard Crestez:
> When the root complex suspends it must send a PME_Turn_Off TLP.
> Implement this by asserting the "turnoff" reset.
> 
> On imx7d this functionality is part of the SRC and exposed through the
> linux reset-controller subsystem. On imx6 equivalent bits are in the
> IOMUXC GPR area which the imx6-pcie driver accesses directly.
> 
> This is only for imx7d right now but it's deliberately implemented as an
> optional reset, ignoring the chip variant:
> * Older dtbs won't have this reset so it will be ignored.
> * Future chips might also expose this as a reset controller.
> 
> For example imx8m (not yet supported) has the exact same
> PCIE_CTRL_APPS_TURNOFF bit in the same location.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>

Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>

> ---
> Âdrivers/pci/controller/dwc/pci-imx6.c | 24 ++++++++++++++++++++++++
> Â1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 6ba16fd1373c..2bf80f1ad852 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -50,10 +50,11 @@ struct imx6_pcie {
> > > Â	struct clk		*pcie_inbound_axi;
> > > Â	struct clk		*pcie;
> > > Â	struct regmap		*iomuxc_gpr;
> > > Â	struct reset_control	*pciephy_reset;
> > > Â	struct reset_control	*apps_reset;
> > > +	struct reset_control	*turnoff_reset;
> > Â	enum imx6_pcie_variants variant;
> > > Â	u32			tx_deemph_gen1;
> > > Â	u32			tx_deemph_gen2_3p5db;
> > > Â	u32			tx_deemph_gen2_6db;
> > > Â	u32			tx_swing_full;
> @@ -812,10 +813,25 @@ static void imx6_pcie_ltssm_disable(struct device *dev)
> > Â	default:
> > Â		dev_err(dev, "ltssm_disable not supported\n");
> > Â	}
> Â}
> Â
> +static void imx6_pcie_pm_turnoff(struct imx6_pcie *imx6_pcie)
> +{
> > +	reset_control_assert(imx6_pcie->turnoff_reset);
> > +	reset_control_deassert(imx6_pcie->turnoff_reset);
> +
> > +	/*
> > +	Â* Components with an upstream port must respond to
> > +	Â* PME_Turn_Off with PME_TO_Ack but we can't check.
> > +	Â*
> > +	Â* The standard recommends a 1-10ms timeout after which to
> > +	Â* proceed anyway as if acks were received.
> > +	Â*/
> > +	usleep_range(1000, 10000);
> +}
> +
> Âstatic void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
> Â{
> > Â	clk_disable_unprepare(imx6_pcie->pcie);
> > Â	clk_disable_unprepare(imx6_pcie->pcie_phy);
> > Â	clk_disable_unprepare(imx6_pcie->pcie_bus);
> @@ -832,10 +848,11 @@ static int imx6_pcie_suspend_noirq(struct device *dev)
> > Â	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
> Â
> > Â	if (imx6_pcie->variant != IMX7D)
> > Â		return 0;
> Â
> > +	imx6_pcie_pm_turnoff(imx6_pcie);
> > Â	imx6_pcie_clk_disable(imx6_pcie);
> > Â	imx6_pcie_ltssm_disable(dev);
> Â
> > Â	return 0;
> Â}
> @@ -959,10 +976,17 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> > Â		break;
> > Â	default:
> > Â		break;
> > Â	}
> Â
> > +	/* Grab turnoff reset */
> > +	imx6_pcie->turnoff_reset = devm_reset_control_get_optional_exclusive(dev, "turnoff");
> > +	if (IS_ERR(imx6_pcie->turnoff_reset)) {
> > +		dev_err(dev, "Failed to get TURNOFF reset control\n");
> > +		return PTR_ERR(imx6_pcie->turnoff_reset);
> > +	}
> +
> > Â	/* Grab GPR config register range */
> > Â	imx6_pcie->iomuxc_gpr =
> > Â		Âsyscon_regmap_lookup_by_compatible("fsl,imx6q-iomuxc-gpr");
> > Â	if (IS_ERR(imx6_pcie->iomuxc_gpr)) {
> > Â		dev_err(dev, "unable to find iomuxc registers\n");