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

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Message-ID: <1795efc94a7b87fb4d9f769e03ce21c6@codeaurora.org>
Date:   Thu, 26 Aug 2021 12:51:53 +0530
From:   Prasad Malisetty <pmaliset@...eaurora.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Stephen Boyd <swboyd@...omium.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

On 2021-08-26 02:55, Bjorn Helgaas wrote:
> [+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
> 
Hi Bjorn,

I agree on your point, but the main reason is to use compatible in 
get_resources_2_7_0 is same hardware version. For SM8250 & SC7280 
platforms, the hw version is same. Since we can't have a separate ops 
for SC7280, we are using compatible method in get_resources_2_7_0 to 
differentiate SM8250 and SC7280.

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