Messages in this thread | | | Date | Fri, 16 Jul 2021 12:23:58 +0530 | From | Prasad Malisetty <> | Subject | Re: [PATCH v3 4/4] PCIe: qcom: Add support to control pipe clk mux |
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On 2021-07-12 21:33, Bjorn Andersson wrote: > On Tue 22 Jun 11:00 CDT 2021, Prasad Malisetty wrote: > >> pipe-clk mux needs to switch between pipe_clk > > If you spell "pipe-clk mux" as "gcc_pcie_N_pipe_clk_src" there's no > ambiguity in which clock you refer to. > Sure, it looks fine, I will modify accordingly.
>> and XO as part of LPM squence. This is done by setting >> pipe_clk mux as parent of pipe_clk after phy init. > > I thought the two possible cases where: > > xo -> gcc_pcie_N_pipe_clk_src -> gcc_pcie_N_pipe_clk > PHY::pipe_clk -> gcc_pcie_N_pipe_clk_src -> gcc_pcie_N_pipe_clk > > But here you're saying that you're setting the parent of PHY::pipe_clk > to gcc_pcie_N_pipe_clk? > Yeah, I will correct that statement.
>> This is a new requirement for sc7280. >> For accessing to DBI registers during L23, >> need to switch the pipe clock with free-running >> clock (TCXO) using GCC’s registers > > So in previous platforms we could access DBI registers, in L23, without > any clock? > > What happens if we use xo as parent for the pipe clock > From SC7280 onwards, POR value for "gcc_pcie_N_pipe_clk_src" is TCX0. we need TCXO as parent to enable gdsc and then once PHY init successful we are changing gcc_pcie_N_pipe_clk_src to PHY pipe clk. In system suspend call back GDSC will be disabled and gcc_pcie_N_pipe_clk_src changed to TCX0. In the same way resume call back switching back gcc_pcie_N_pipe_clk_src to PHY pipe clk .
>> >> Signed-off-by: Prasad Malisetty <pmaliset@codeaurora.org> >> --- >> drivers/pci/controller/dwc/pcie-qcom.c | 22 ++++++++++++++++++++++ >> 1 file changed, 22 insertions(+) >> >> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c >> b/drivers/pci/controller/dwc/pcie-qcom.c >> index 8a7a300..80e9ee4 100644 >> --- a/drivers/pci/controller/dwc/pcie-qcom.c >> +++ b/drivers/pci/controller/dwc/pcie-qcom.c >> @@ -166,6 +166,9 @@ struct qcom_pcie_resources_2_7_0 { >> struct regulator_bulk_data supplies[2]; >> struct reset_control *pci_reset; >> struct clk *pipe_clk; >> + struct clk *pipe_clk_mux; >> + struct clk *pipe_ext_src; >> + struct clk *ref_clk_src; >> }; >> >> union qcom_pcie_resources { >> @@ -1167,6 +1170,20 @@ 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")) { > > So this is the first 2.7.0 that has this need? Are we just going to add > more compatibles to this list going forward? > Will check and confirm whether above change will be applicable to future targets or not.
>> + res->pipe_clk_mux = devm_clk_get(dev, "pipe_mux"); >> + if (IS_ERR(res->pipe_clk_mux)) >> + return PTR_ERR(res->pipe_clk_mux); > > So this is gcc_pcie_N_pipe_clk_src? > Yes >> + >> + res->pipe_ext_src = devm_clk_get(dev, "phy_pipe"); >> + if (IS_ERR(res->pipe_ext_src)) >> + return PTR_ERR(res->pipe_ext_src); > > And this is the pipe_clk coming out of the PHY (What I call > PHY::pipe_clk above)? > Yes >> + >> + res->ref_clk_src = devm_clk_get(dev, "ref"); >> + if (IS_ERR(res->ref_clk_src)) >> + return PTR_ERR(res->ref_clk_src); > > And this is TCXO? > Yes >> + } >> + >> res->pipe_clk = devm_clk_get(dev, "pipe"); >> return PTR_ERR_OR_ZERO(res->pipe_clk); >> } >> @@ -1255,6 +1272,11 @@ static void qcom_pcie_deinit_2_7_0(struct >> qcom_pcie *pcie) >> static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie) >> { >> struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0; >> + struct dw_pcie *pci = pcie->pci; >> + struct device *dev = pci->dev; >> + >> + if (of_device_is_compatible(dev->of_node, "qcom,pcie-sc7280")) >> + clk_set_parent(res->pipe_clk_mux, res->pipe_ext_src); >> > > So after phy_power_on() (not "phy init" as you say in the commit > message, perhaps you don't mean phy_init() but in general terms "phy > initialization") you need to make sure that gcc_pcie_N_pipe_clk_src is > actually fed by PHY::pipe_clk? > > 1) What's the gcc_pcie_N_pipe_clk_src parent before this? > TCXO is POR value.
> 2) Will the PHY initialization really succeed if the pipe_clk feeding > back from gcc isn't based on the PHY's pipe_clk? Is this a change in > sc7280? > PHY init will be successful but PCIe link will not be initialized. yes, this change is only applicable to SC7280.
> 3) In the commit message you're talking about the need to make XO the > parent of gcc_pcie_N_pipe_clk_src during L23, where in this patch does > that happen? > Changes are in validation stage. will submit them soon in coming releases. Just mentioned the purpose of mux settings.
> Regards, > Bjorn > >> return clk_prepare_enable(res->pipe_clk); >> } >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora >> Forum, >> a Linux Foundation Collaborative Project >>
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