Re: [PATCH v3] PCI: imx6: Add PHY reference clock source support

[Ilya Ledvich <ilya@xxxxxxxxxxxxxx>]

Hi Lucas,

On 01/08/2018 12:43 PM, Lucas Stach wrote:
> Am Donnerstag, den 04.01.2018, 15:52 +0200 schrieb Ilya Ledvich:
> > i.MX7D variant of the IP can use either Crystal Oscillator input
> > or internal clock input as a Reference Clock input for PCIe PHY.
> > Add support for an optional property 'fsl,pcie-phy-refclk-internal'.
> > If present then an internal clock input is used as PCIe PHY
> > reference clock source. By default an external oscillator input
> > is still used.
> >
> > Verified on Compulab SBC-iMX7 Single Board Computer.
>
> Sorry to get in late here, but I would rather have the external clock
> input modeled as a real clock and only use the internal clock if that
> isn't present.

I tried to follow the logic described in the iMX7 TRM, where external 
oscillator is a default option. Additionally, the external clock input 
model you've suggested, requires additional changes in the iMX7 SabreSD 
board (and probably other boards which use an external input too) 
devicetree files.

> Are you even sure that the i.MX7 clock you mention isn't the already
> documented "pcie_bus" clock? This one is also allowed to be sourced
> externally on the i.MX6.

To the best of my understanding it's not the pcie_bus clock, but I'm 
absolutely sure. Could anybody from the BSP team guys elaborate on this 
issue? Thanks a lot!
Best regards,
Ilya.

> > ---
> > changes since V2:
> > 	add a vendor prefix 'fsl' to a new property
> >
> >   Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt | 5 +++++
> >   drivers/pci/dwc/pci-imx6.c                               | 8
> > +++++++-
> >   2 files changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > index 7b1e48b..1591a6a 100644
> > --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> > @@ -50,6 +50,11 @@ Additional required properties for imx7d-pcie:
> >   	       - "pciephy"
> >   	       - "apps"
> >   
> > +Additional optional properties for imx7d-pcie:
> > +- fsl,pcie-phy-refclk-internal: If present then an internal PLL
> > input is used
> > +  as PCIe PHY reference clock source. By default an external
> > oscillator input
> > +  is used.
> > +
> >   Example:
> >   
> >   	pcie@0x01000000 {
> > diff --git a/drivers/pci/dwc/pci-imx6.c b/drivers/pci/dwc/pci-imx6.c
> > index b734835..36812d3 100644
> > --- a/drivers/pci/dwc/pci-imx6.c
> > +++ b/drivers/pci/dwc/pci-imx6.c
> > @@ -61,6 +61,7 @@ struct imx6_pcie {
> >   	u32			tx_swing_low;
> >   	int			link_gen;
> >   	struct regulator	*vpcie;
> > +	bool			pciephy_refclk_sel;
> >   };
> >   
> >   /* Parameters for the waiting for PCIe PHY PLL to lock on i.MX7 */
> > @@ -474,7 +475,9 @@ static void imx6_pcie_init_phy(struct imx6_pcie
> > *imx6_pcie)
> >   	switch (imx6_pcie->variant) {
> >   	case IMX7D:
> >   		regmap_update_bits(imx6_pcie->iomuxc_gpr,
> > IOMUXC_GPR12,
> > -				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
> > 0);
> > +				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
> > +				   imx6_pcie->pciephy_refclk_sel ?
> > +				   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL :
> > 0);
> >   		break;
> >   	case IMX6SX:
> >   		regmap_update_bits(imx6_pcie->iomuxc_gpr,
> > IOMUXC_GPR12,
> > @@ -840,6 +843,9 @@ static int imx6_pcie_probe(struct platform_device
> > *pdev)
> >   		imx6_pcie->vpcie = NULL;
> >   	}
> >   
> > +	imx6_pcie->pciephy_refclk_sel =
> > +		of_property_read_bool(node, "fsl,pcie-phy-refclk-
> > internal");
> > +
> >   	platform_set_drvdata(pdev, imx6_pcie);
> >   
> >   	ret = imx6_add_pcie_port(imx6_pcie, pdev);