FROMLIST: 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.

Link: https://lore.kernel.org/linux-pci/20240210-topic-8280_pcie-v2-0-1cef4b606883@linaro.org/
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Krishna Chaitanya Chundru <krichai@qti.qualcomm.com>

Author: konradybcio

drivers/pci/controller/dwc/pcie-qcom.c

@@ -944,27 +944,27 @@ 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);
 
@@ -994,8 +994,6 @@ 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);