[PATCH] Revert "PCI: qcom: Remove custom ASPM enablement code"

[Bjorn Helgaas <helgaas@kernel.org>]

From: Bjorn Helgaas <bhelgaas@google.com>

This reverts commit a729c16646198872e345bf6c48dbe540ad8a9753.

Prior to a729c1664619 ("PCI: qcom: Remove custom ASPM enablement code"),
the qcom controller driver enabled ASPM, including L0s, L1, and L1 PM
Substates, for all devices powered on at the time the controller driver
enumerates them.

ASPM was *not* enabled for devices powered on later by pwrctrl (unless the
kernel was built with PCIEASPM_POWERSAVE or PCIEASPM_POWER_SUPERSAVE, or
the user enabled ASPM via module parameter or sysfs).

After f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for
devicetree platforms"), the PCI core enabled all ASPM states for all
devices whether powered on initially or by pwrctrl, so a729c1664619 was
unnecessary and reverted.

But f3ac2ff14834 was too aggressive and broke platforms that didn't support
CLKREQ# or required device-specific configuration for L1 Substates, so
df5192d9bb0e ("PCI/ASPM: Enable only L0s and L1 for devicetree platforms")
enabled only L0s and L1.

On Qualcomm platforms, this left L1 Substates disabled, which was a
regression.  Revert a729c1664619 so L1 Substates will be enabled on devices
that are initially powered on.  Devices powered on by pwrctrl will be
addressed later.

Fixes: df5192d9bb0e ("PCI/ASPM: Enable only L0s and L1 for devicetree platforms")
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 32 ++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 6948824642dc..c48a20602d7f 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -247,6 +247,7 @@ struct qcom_pcie_ops {
 	int (*get_resources)(struct qcom_pcie *pcie);
 	int (*init)(struct qcom_pcie *pcie);
 	int (*post_init)(struct qcom_pcie *pcie);
+	void (*host_post_init)(struct qcom_pcie *pcie);
 	void (*deinit)(struct qcom_pcie *pcie);
 	void (*ltssm_enable)(struct qcom_pcie *pcie);
 	int (*config_sid)(struct qcom_pcie *pcie);
@@ -1038,6 +1039,25 @@ static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
 	return 0;
 }
 
+static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata)
+{
+	/*
+	 * Downstream devices need to be in D0 state before enabling PCI PM
+	 * substates.
+	 */
+	pci_set_power_state_locked(pdev, PCI_D0);
+	pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
+
+	return 0;
+}
+
+static void qcom_pcie_host_post_init_2_7_0(struct qcom_pcie *pcie)
+{
+	struct dw_pcie_rp *pp = &pcie->pci->pp;
+
+	pci_walk_bus(pp->bridge->bus, qcom_pcie_enable_aspm, NULL);
+}
+
 static void qcom_pcie_deinit_2_7_0(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
@@ -1312,9 +1332,19 @@ static void qcom_pcie_host_deinit(struct dw_pcie_rp *pp)
 	pcie->cfg->ops->deinit(pcie);
 }
 
+static void qcom_pcie_host_post_init(struct dw_pcie_rp *pp)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+
+	if (pcie->cfg->ops->host_post_init)
+		pcie->cfg->ops->host_post_init(pcie);
+}
+
 static const struct dw_pcie_host_ops qcom_pcie_dw_ops = {
 	.init		= qcom_pcie_host_init,
 	.deinit		= qcom_pcie_host_deinit,
+	.post_init	= qcom_pcie_host_post_init,
 };
 
 /* Qcom IP rev.: 2.1.0	Synopsys IP rev.: 4.01a */
@@ -1376,6 +1406,7 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
 	.get_resources = qcom_pcie_get_resources_2_7_0,
 	.init = qcom_pcie_init_2_7_0,
 	.post_init = qcom_pcie_post_init_2_7_0,
+	.host_post_init = qcom_pcie_host_post_init_2_7_0,
 	.deinit = qcom_pcie_deinit_2_7_0,
 	.ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
 	.config_sid = qcom_pcie_config_sid_1_9_0,
@@ -1386,6 +1417,7 @@ static const struct qcom_pcie_ops ops_1_21_0 = {
 	.get_resources = qcom_pcie_get_resources_2_7_0,
 	.init = qcom_pcie_init_2_7_0,
 	.post_init = qcom_pcie_post_init_2_7_0,
+	.host_post_init = qcom_pcie_host_post_init_2_7_0,
 	.deinit = qcom_pcie_deinit_2_7_0,
 	.ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
 };
-- 
2.43.0