Re: [PATCH] PCI: imx: Add imx6sx suspend/resume support

[Philipp Zabel <p.zabel@pengutronix.de>]

Hi Leonard,

On Wed, 2018-10-31 at 11:02 +0000, Leonard Crestez wrote:
> On 10/8/2018 8:38 PM, Leonard Crestez wrote:
> > Enable PCI suspend/resume support on imx6sx socs. This is similar to
> > imx7d with a few differences:
> > 
> > * The PM_Turn_Off bit is exposed through an IOMUX GPR, like all other
> > pcie control bits on 6sx.
> > * The pcie_inbound_axi clk needs to be turned off in suspend. On resume
> > it is restored via resume -> deassert_core_reset -> enable_ref_clk.
> > 
> > Most of the resume logic is shared with the initial reset after probe.
> > 
> > Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> 
> This is a gentle reminder that this patch was posted ~3 weeks ago and 
> there is yet no reply. It's a mostly straight-forward extension of imx7d 
> pci suspend/resume support to a different SOC.
> 
> Lucas/Philipp: can you please take a brief look?

This is a bit out of my wheelhouse, but I'll try my best.

> > ---
> >   drivers/pci/controller/dwc/pci-imx6.c       | 40 ++++++++++++++++++---
> >   include/linux/mfd/syscon/imx6q-iomuxc-gpr.h |  1 +
> >   2 files changed, 36 insertions(+), 5 deletions(-)
> > 
> > Patch is again linux-next, meant to apply here:
> >   https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git/log/?h=pci/dwc
> > 
> > This is quite an old patch, mostly did it to prove that imx7d suspend
> > support is indeed generic.
> > 
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> > index 2cbef2d7c207..6171171db1fc 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -771,12 +771,29 @@ static void imx6_pcie_ltssm_disable(struct device *dev)
> >   	}
> >   }
> >   
> >   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);
> > +	struct device *dev = imx6_pcie->pci->dev;
> > +
> > +	/*
> > +	 * Some variants have a turnoff reset in DT while
> > +	 * others poke at iomuxc registers.
> > +	 */
> > +	if (imx6_pcie->turnoff_reset) {
> > +		reset_control_assert(imx6_pcie->turnoff_reset);
> > +		reset_control_deassert(imx6_pcie->turnoff_reset);
> > +	} else if (imx6_pcie->variant == IMX6SX) {
> > +		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> > +				IMX6SX_GPR12_PCIE_PM_TURN_OFF,
> > +				IMX6SX_GPR12_PCIE_PM_TURN_OFF);
> > +		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> > +				IMX6SX_GPR12_PCIE_PM_TURN_OFF, 0);
> > +	} else {
> > +		dev_err(dev, "PME_Turn_Off not implemented\n");
> > +		return;
> > +	}

I'd use switch(imx6_pcie->variant) for consistency with the other places
where different variants need to be handled separately.

> >   
> >   	/*
> >   	 * Components with an upstream port must respond to
> >   	 * PME_Turn_Off with PME_TO_Ack but we can't check.
> >   	 *
> > @@ -790,22 +807,35 @@ static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
> >   {
> >   	clk_disable_unprepare(imx6_pcie->pcie);
> >   	clk_disable_unprepare(imx6_pcie->pcie_phy);
> >   	clk_disable_unprepare(imx6_pcie->pcie_bus);
> >   
> > -	if (imx6_pcie->variant == IMX7D) {
> > +	switch (imx6_pcie->variant) {
> > +	case IMX6SX:
> > +		clk_disable_unprepare(imx6_pcie->pcie_inbound_axi);
> > +		break;
> > +	case IMX7D:
> >   		regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
> >   				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
> >   				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
> > +		break;
> > +	default:
> > +		break;
> >   	}

This disables the ref clock. Should this be split into a separate
function imx6_pcie_disable_ref_clk() for symmetry with the already
existing imx6_pcie_enable_ref_clk() ?

That could then also be used to disable pcie_inbound_axi in the error
path of imx6_pcie_deassert_core_reset().

> >   }
> >   
> > +static inline bool imx6_pcie_supports_suspend(struct imx6_pcie *imx6_pcie)
> > +{
> > +	return (imx6_pcie->variant == IMX7D ||
> > +		imx6_pcie->variant == IMX6SX);
> > +}
> > +
> >   static int imx6_pcie_suspend_noirq(struct device *dev)
> >   {
> >   	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
> >   
> > -	if (imx6_pcie->variant != IMX7D)
> > +	if (!imx6_pcie_supports_suspend(imx6_pcie))
> >   		return 0;
> >   
> >   	imx6_pcie_pm_turnoff(imx6_pcie);
> >   	imx6_pcie_clk_disable(imx6_pcie);
> >   	imx6_pcie_ltssm_disable(dev);
> > @@ -817,11 +847,11 @@ static int imx6_pcie_resume_noirq(struct device *dev)
> >   {
> >   	int ret;
> >   	struct imx6_pcie *imx6_pcie = dev_get_drvdata(dev);
> >   	struct pcie_port *pp = &imx6_pcie->pci->pp;
> >   
> > -	if (imx6_pcie->variant != IMX7D)
> > +	if (!imx6_pcie_supports_suspend(imx6_pcie))
> >   		return 0;
> >   
> >   	imx6_pcie_assert_core_reset(imx6_pcie);
> >   	imx6_pcie_init_phy(imx6_pcie);
> >   	imx6_pcie_deassert_core_reset(imx6_pcie);
> > diff --git a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> > index 6c1ad160ed87..c1b25f5e386d 100644
> > --- a/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> > +++ b/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
> > @@ -438,10 +438,11 @@
> >   #define IMX6SX_GPR5_DISP_MUX_DCIC1_LCDIF1		(0x0 << 1)
> >   #define IMX6SX_GPR5_DISP_MUX_DCIC1_LVDS			(0x1 << 1)
> >   #define IMX6SX_GPR5_DISP_MUX_DCIC1_MASK			(0x1 << 1)
> >   
> >   #define IMX6SX_GPR12_PCIE_TEST_POWERDOWN		BIT(30)
> > +#define IMX6SX_GPR12_PCIE_PM_TURN_OFF			BIT(16)
> >   #define IMX6SX_GPR12_PCIE_RX_EQ_MASK			(0x7 << 0)
> >   #define IMX6SX_GPR12_PCIE_RX_EQ_2			(0x2 << 0)
> >   
> >   /* For imx6ul iomux gpr register field define */
> >   #define IMX6UL_GPR1_ENET1_CLK_DIR		(0x1 << 17)
> > 

regards
Philipp