linux-kernel - Re: [PATCH] imx8mm-venice-gw7902: update pci refclk

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Date:   Fri, 29 Apr 2022 09:04:13 -0700
From:   Tim Harvey <tharvey@...eworks.com>
To:     Shawn Guo <shawnguo@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Richard Zhu <hongxing.zhu@....com>
Subject: Re: [PATCH] imx8mm-venice-gw7902: update pci refclk

On Mon, Apr 18, 2022 at 12:57 AM Shawn Guo <shawnguo@...nel.org> wrote:
>
> On Mon, Apr 11, 2022 at 12:44:23PM -0700, Tim Harvey wrote:
> > On Sun, Apr 10, 2022 at 6:31 PM Shawn Guo <shawnguo@...nel.org> wrote:
> > >
> > > On Tue, Apr 05, 2022 at 01:06:25PM -0700, Tim Harvey wrote:
> > > > Use the correct PCI clock bindings.
> > >
> > > Please improve the commit log to explain why clock "pcie_phy" can be
> > > dropped.
> > >
> >
> > Shawn,
> >
> > The original PCIe bindings for this board were wrong - they were from
> > a version of the bindings that was not yet approved (my mistake) and
> > I'm just trying to bring them up to date.
> >
> > That said, I looked at the latest fsl,imx6q-pcie.yaml dt-bindings [1]
> > and see that there should be a min of 3 clocks called 'pcie',
> > 'pcie_bus', and 'pcie_phy'. However I notice that all of the current
> > imx8mm boards that enable PCI have clock-names of 'pcie', 'pcie_aux',
> > and 'pcie_bus'. It seems like all the imx8mm boards having pcie have
> > clock-names this way:
> >
> > arch/arm64/boot/dts/freescale/imx8mm-beacon-baseboard.dtsi
> > arch/arm64/boot/dts/freescale/imx8mm-evk.dtsi
> > arch/arm64/boot/dts/freescale/imx8mm-tqma8mqml-mba8mx.dts
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw71xx.dtsi
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw72xx.dtsi
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw73xx.dtsi
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw7901.dts
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw7902.dts
> > arch/arm64/boot/dts/freescale/imx8mm-venice-gw7903.dts
> >
> > Does the binding need to change or do the clock names need to change
> > in the above?
>
> If the bindings is approved/correct, device tree should match bindings.
>

Shawn,

I think the bindings are wrong.

Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml has [1]:

  clocks:
    minItems: 3
    items:
      - description: PCIe bridge clock.
      - description: PCIe bus clock.
      - description: PCIe PHY clock.
      - description: Additional required clock entry for imx6sx-pcie,
          imx8mq-pcie.

  clock-names:
    minItems: 3
    items:
      - const: pcie
      - const: pcie_bus
      - const: pcie_phy
      - const: pcie_inbound_axi for imx6sx-pcie, pcie_aux for imx8mq-pcie

This indicates the "pcie_phy" clock is required yet
drivers/pci/controller/dwc/pci-imx6.c [2] doesn't require it if it has
an abstract PHY driver which is the case for IMX8M (and that's why my
patch drops it)

Additionally I note that the 4th clock described in the bindings could
use some clarification for imx8mm-pcie as for this "pcie_aux" is
required.

Best Regards,

Tim
[1] https://elixir.bootlin.com/linux/v5.18-rc4/source/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.yaml
[2] https://elixir.bootlin.com/linux/v5.18-rc4/source/drivers/pci/controller/dwc/pci-imx6.c#L1140