[PATCH v3 5/6] PCI: qcom: Add support for host_stop_link() & host_start_link()

[Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>]

For the switches like QPS615 which needs to configure it before
the PCIe link is established.

If the link is up, the boatloader might powered and configured the
endpoint/switch already. In that case don't touch PCIe link else
assert the PERST# and disable LTSSM bit so that PCIe controller
will not participate in the link training as part of host_stop_link().

De-assert the PERST# and enable LTSSM bit back in host_start_link().

Introduce ltssm_disable function op to stop the link training.

Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 39 ++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index ef44a82be058..048aea94e319 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -246,6 +246,7 @@ struct qcom_pcie_ops {
 	void (*host_post_init)(struct qcom_pcie *pcie);
 	void (*deinit)(struct qcom_pcie *pcie);
 	void (*ltssm_enable)(struct qcom_pcie *pcie);
+	void (*ltssm_disable)(struct qcom_pcie *pcie);
 	int (*config_sid)(struct qcom_pcie *pcie);
 };
 
@@ -617,6 +618,41 @@ static int qcom_pcie_post_init_1_0_0(struct qcom_pcie *pcie)
 	return 0;
 }
 
+static int qcom_pcie_host_start_link(struct dw_pcie *pci)
+{
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+
+	if (!dw_pcie_link_up(pcie->pci))  {
+		qcom_ep_reset_deassert(pcie);
+
+		if (pcie->cfg->ops->ltssm_enable)
+			pcie->cfg->ops->ltssm_enable(pcie);
+	}
+
+	return 0;
+}
+
+static void qcom_pcie_host_stop_link(struct dw_pcie *pci)
+{
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+
+	if (!dw_pcie_link_up(pcie->pci))  {
+		qcom_ep_reset_assert(pcie);
+
+		if (pcie->cfg->ops->ltssm_disable)
+			pcie->cfg->ops->ltssm_disable(pcie);
+	}
+}
+
+static void qcom_pcie_2_3_2_ltssm_disable(struct qcom_pcie *pcie)
+{
+	u32 val;
+
+	val = readl(pcie->parf + PARF_LTSSM);
+	val &= ~LTSSM_EN;
+	writel(val, pcie->parf + PARF_LTSSM);
+}
+
 static void qcom_pcie_2_3_2_ltssm_enable(struct qcom_pcie *pcie)
 {
 	u32 val;
@@ -1361,6 +1397,7 @@ static const struct qcom_pcie_ops ops_1_9_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,
+	.ltssm_disable = qcom_pcie_2_3_2_ltssm_disable,
 	.config_sid = qcom_pcie_config_sid_1_9_0,
 };
 
@@ -1418,6 +1455,8 @@ static const struct qcom_pcie_cfg cfg_sc8280xp = {
 static const struct dw_pcie_ops dw_pcie_ops = {
 	.link_up = qcom_pcie_link_up,
 	.start_link = qcom_pcie_start_link,
+	.host_start_link = qcom_pcie_host_start_link,
+	.host_stop_link = qcom_pcie_host_stop_link,
 };
 
 static int qcom_pcie_icc_init(struct qcom_pcie *pcie)

-- 
2.34.1