linux-kernel - [PATCH v3 1/2] PCI: qcom: reshuffle reset logic in 2_7

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Message-Id: <20240210-topic-8280_pcie-v3-1-ee7af6f892a0@linaro.org>
Date: Wed, 27 Mar 2024 20:49:08 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Johan Hovold <johan+linaro@...nel.org>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: [PATCH v3 1/2] PCI: qcom: reshuffle reset logic in 2_7_0 .init

At least on SC8280XP, if the PCIe reset is asserted, the corresponding
AUX_CLK will be stuck at 'off'. This has not been an issue so far,
since the reset is both left de-asserted by the previous boot stages
and the driver only toggles it briefly in .init.

As part of the upcoming suspend procedure however, the reset will be
held asserted.

Assert the reset (which may end up being a NOP in some cases) and
de-assert it back *before* turning on the clocks in preparation for
introducing RC powerdown and reinitialization.

Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 14772edcf0d3..d875a9b2b7be 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -925,27 +925,27 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
 		return ret;
 	}
 
-	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
-	if (ret < 0)
-		goto err_disable_regulators;
-
+	/* Assert the reset to hold the RC in a known state */
 	ret = reset_control_assert(res->rst);
 	if (ret) {
 		dev_err(dev, "reset assert failed (%d)\n", ret);
-		goto err_disable_clocks;
+		goto err_disable_regulators;
 	}
-
 	usleep_range(1000, 1500);
 
+	/* GCC_PCIE_n_AUX_CLK won't come up if the reset is asserted */
 	ret = reset_control_deassert(res->rst);
 	if (ret) {
 		dev_err(dev, "reset deassert failed (%d)\n", ret);
-		goto err_disable_clocks;
+		goto err_disable_regulators;
 	}
-
 	/* Wait for reset to complete, required on SM8450 */
 	usleep_range(1000, 1500);
 
+	ret = clk_bulk_prepare_enable(res->num_clks, res->clks);
+	if (ret < 0)
+		goto err_disable_regulators;
+
 	/* configure PCIe to RC mode */
 	writel(DEVICE_TYPE_RC, pcie->parf + PARF_DEVICE_TYPE);
 
@@ -976,8 +976,6 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
 	writel(val, pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
 
 	return 0;
-err_disable_clocks:
-	clk_bulk_disable_unprepare(res->num_clks, res->clks);
 err_disable_regulators:
 	regulator_bulk_disable(ARRAY_SIZE(res->supplies), res->supplies);
 

-- 
2.44.0