linux-kernel - Re: [PATCH v5 4/4] PCI: qcom: Switch pcie_1_pipe_clk

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Date:   Wed, 25 Aug 2021 16:25:49 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Prasad Malisetty <pmaliset@...eaurora.org>, agross@...nel.org,
        bhelgaas@...gle.com, bjorn.andersson@...aro.org,
        lorenzo.pieralisi@....com, robh+dt@...nel.org,
        svarbanov@...sol.com, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, dianders@...omium.org,
        mka@...omium.org, vbadigan@...eaurora.org, sallenki@...eaurora.org,
        manivannan.sadhasivam@...aro.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v5 4/4] PCI: qcom: Switch pcie_1_pipe_clk_src after PHY
 init in SC7280

[+cc linux-pci; patches to drivers/pci/ should always be cc'd there]

On Wed, Aug 25, 2021 at 07:30:09PM +0000, Stephen Boyd wrote:
> Quoting Prasad Malisetty (2021-08-24 01:10:48)
> > On 2021-08-17 22:56, Prasad Malisetty wrote:
> > > On 2021-08-10 09:38, Prasad Malisetty wrote:
> > >> On the SC7280, By default the clock source for pcie_1_pipe is
> > >> TCXO for gdsc enable. But after the PHY is initialized, the clock
> > >> source must be switched to gcc_pcie_1_pipe_clk from TCXO.
> > >>
> > >> Signed-off-by: Prasad Malisetty <pmaliset@...eaurora.org>
> > >> ---
> > >>  drivers/pci/controller/dwc/pcie-qcom.c | 18 ++++++++++++++++++
> > >>  1 file changed, 18 insertions(+)
> > >>
> > >> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c
> > >> b/drivers/pci/controller/dwc/pcie-qcom.c
> > >> index 8a7a300..39e3b21 100644
> > >> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > >> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > >> @@ -166,6 +166,8 @@ struct qcom_pcie_resources_2_7_0 {
> > >>      struct regulator_bulk_data supplies[2];
> > >>      struct reset_control *pci_reset;
> > >>      struct clk *pipe_clk;
> > >> +    struct clk *gcc_pcie_1_pipe_clk_src;
> > >> +    struct clk *phy_pipe_clk;
> > >>  };
> > >>
> > >>  union qcom_pcie_resources {
> > >> @@ -1167,6 +1169,16 @@ static int qcom_pcie_get_resources_2_7_0(struct
> > >> qcom_pcie *pcie)
> > >>      if (ret < 0)
> > >>              return ret;
> > >>
> > >> +    if (of_device_is_compatible(dev->of_node, "qcom,pcie-sc7280")) {
> > >> +            res->gcc_pcie_1_pipe_clk_src = devm_clk_get(dev, "pipe_mux");
> > >> +            if (IS_ERR(res->gcc_pcie_1_pipe_clk_src))
> > >> +                    return PTR_ERR(res->gcc_pcie_1_pipe_clk_src);
> > >> +
> > >> +            res->phy_pipe_clk = devm_clk_get(dev, "phy_pipe");
> > >> +            if (IS_ERR(res->phy_pipe_clk))
> > >> +                    return PTR_ERR(res->phy_pipe_clk);
> > >> +    }
> > >
> > > I would like to check is there any other better approach instead of
> > > compatible method here as well or is it fine to use compatible method.
> 
> I'd prefer the compatible method. If nobody is responding then it's best
> to just resend the patches with the approach you prefer instead of
> waiting for someone to respond to a review comment.

I'm missing some context here, so I'm not exactly sure what your
question is, Prasad, but IMO drivers generally should not need to use
of_device_is_compatible() if they've already called
of_device_get_match_data() (as qcom_pcie_probe() has).

of_device_is_compatible() does basically the same work of looking for
a match in qcom_pcie_match[] that of_device_get_match_data() does, so
it seems pointless to repeat it.

I am a little confused because while [1] adds "qcom,pcie-sc7280" to
qcom,pcie.txt, I don't see a patch that adds it to qcom_pcie_match[].

Bjorn

[1] https://lore.kernel.org/linux-arm-msm/1628568516-24155-2-git-send-email-pmaliset@codeaurora.org/