linux-kernel - [PATCH v2 04/10] PCIe: qcom: Fixed pcie_phy

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Date:   Thu,  2 Apr 2020 14:11:41 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Andy Gross <agross@...nel.org>
Cc:     Ansuel Smith <ansuelsmth@...il.com>,
        Abhishek Sahu <absahu@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Stanimir Varbanov <svarbanov@...sol.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 04/10] PCIe: qcom: Fixed pcie_phy_clk branch issue

Following backtraces are observed in PCIe deinit operation.

 Hardware name: Qualcomm (Flattened Device Tree)
 (unwind_backtrace) from [] (show_stack+0x10/0x14)
 (show_stack) from [] (dump_stack+0x84/0x98)
 (dump_stack) from [] (warn_slowpath_common+0x9c/0xb8)
 (warn_slowpath_common) from [] (warn_slowpath_fmt+0x30/0x40)
 (warn_slowpath_fmt) from [] (clk_branch_wait+0x114/0x120)
 (clk_branch_wait) from [] (clk_core_disable+0xd0/0x1f4)
 (clk_core_disable) from [] (clk_disable+0x24/0x30)
 (clk_disable) from [] (qcom_pcie_deinit_v0+0x6c/0xb8)
 (qcom_pcie_deinit_v0) from [] (qcom_pcie_host_init+0xe0/0xe8)
 (qcom_pcie_host_init) from [] (dw_pcie_host_init+0x3b0/0x538)
 (dw_pcie_host_init) from [] (qcom_pcie_probe+0x20c/0x2e4)

pcie_phy_clk is generated for PCIe controller itself and the
GCC controls its branch operation. This error is coming since
the assert operations turn off the parent clock before branch
clock. Now this patch moves clk_disable_unprepare before assert
operations.

Similarly, during probe function, the clock branch operation
should be done after dessert operation. Currently, it does not
generate any error since bootloader enables the pcie_phy_clk
but the same error is coming during probe, if bootloader
disables pcie_phy_clk.

Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 1fcc7fed8443..596731b54728 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -280,6 +280,7 @@ static void qcom_pcie_deinit_2_1_0(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_resources_2_1_0 *res = &pcie->res.v2_1_0;
 
+	clk_disable_unprepare(res->phy_clk);
 	reset_control_assert(res->pci_reset);
 	reset_control_assert(res->axi_reset);
 	reset_control_assert(res->ahb_reset);
@@ -287,7 +288,6 @@ static void qcom_pcie_deinit_2_1_0(struct qcom_pcie *pcie)
 	reset_control_assert(res->phy_reset);
 	clk_disable_unprepare(res->iface_clk);
 	clk_disable_unprepare(res->core_clk);
-	clk_disable_unprepare(res->phy_clk);
 	clk_disable_unprepare(res->aux_clk);
 	clk_disable_unprepare(res->ref_clk);
 	regulator_bulk_disable(ARRAY_SIZE(res->supplies), res->supplies);
@@ -325,12 +325,6 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
 		goto err_clk_core;
 	}
 
-	ret = clk_prepare_enable(res->phy_clk);
-	if (ret) {
-		dev_err(dev, "cannot prepare/enable phy clock\n");
-		goto err_clk_phy;
-	}
-
 	ret = clk_prepare_enable(res->aux_clk);
 	if (ret) {
 		dev_err(dev, "cannot prepare/enable aux clock\n");
@@ -383,6 +377,12 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
 		return ret;
 	}
 
+	ret = clk_prepare_enable(res->phy_clk);
+	if (ret) {
+		dev_err(dev, "cannot prepare/enable phy clock\n");
+		goto err_deassert_ahb;
+	}
+
 	/* wait for clock acquisition */
 	usleep_range(1000, 1500);
 
@@ -400,8 +400,6 @@ static int qcom_pcie_init_2_1_0(struct qcom_pcie *pcie)
 err_clk_ref:
 	clk_disable_unprepare(res->aux_clk);
 err_clk_aux:
-	clk_disable_unprepare(res->phy_clk);
-err_clk_phy:
 	clk_disable_unprepare(res->core_clk);
 err_clk_core:
 	clk_disable_unprepare(res->iface_clk);
-- 
2.25.1